Column liquid chromatography: equipment and ... - ACS Publications

Anal. Chem. 1992, 64, 255 R-270 R

Column Liquid Chromatography: Equipment and Instrumentation Timothy J. Bahowick, Veeravagu Murugaiah, Andrew W.Sulya, Daniel B. Taylor, and Robert E. Synovec* Center for Process Analytical Chemistry, Department of Chemistry, BG-10, University of Washington, Seattle, Washington 98195

Richard J. Berman, Curtis8 N.R e m , and Edward L.Johnson*

ALPKEM Corporation, 9445 Southwest Ridder Road, Suite 310, Wilsonville, Oregon 97070

INTRODUCTION This review covers the fundamental developments in the field of column liquid chromatography (LC), dealing with equipment and instrumentation, during the period 1990-1991. Our main data base for this review was CA Selects from Dec 1989 to Dec 1991. The literature search included manuscripts, patents, and theses published in English,,French, German, Japanese, and Russian, with some exceptions. This review is not a comprehensive coverage of all LC literature dealing with equipment and instrumentation. Rather, the review reflects our critical selection of fundamental developments in this field of LC. For this reason, atents and theses were considered, although manuscripts ominate the cover e. Your sug estions and comments are welcome and should e addreeset! to the senior authors (E.L.J. and R.E.S.). Reprint re uests should be made to R.E.S. %he review is organized with the followin sections: A, Columns; B, Instrumentation; C, Detectors: eneral Introduction; D, Absorbance Detectors; E, Chemiluminescence Detectors; F, Electrochemical Detectors; G, Fluorescence Detectors; H, Indirect Detection; I, Infrared Detectors; J, LC/MS; K, Optical Activity Detectors; L, Refractive Index Detectors; M. Miscellaneous Detectors. An introductory paragraph covering books and reviews begins each section.

x

Y)

&

A. COLUMNS This section of the review is focused on the general as of column design, hardware, and maintenance. New pac gs are covered in a separate review. Schombur (AI) reviewed column technology and instrumentation for &romatopaphy and ca illary electrophoresis. The effect of miniaturuation in capiaries was discussed. A review of column technology for packed capillary columns (A2) was published. The comparson of f i e ae aration parameters and analysis of binary mixtures by liquifchromatography on ca illary columns, long packed microcolumns and short packerf microcolumns was reported (A3). Capillary columns were found to provide a significant reduction of analysis time and a pressure drop at the system inlet. A mathematical model for capillary chromatogra hy on open columns (A4) was published. Ying and introduced a wa of characterizing retentivity Dorsey of reversed-phase columns. $he role of column variables in re arative HPLC under isocratic conditions was reported y nyder and Cox (A6). The influence of pore structure of silica packing on HPLC column characteristics was reported ( A n . Mallett and Law (A8) demonstrated the com atibility of narrow-bore packed HPLC with conventional Betaction systems. Theoretical discussions of column “dead volume” in LC (A91 and dispersion in the interstitial space of packed columns (A10) were reported.

E?

pA6)

El

Packlng Techniques

A new technique for packing preparative HPLC columns by article sedimentation was reported by Wang and coworters (All). A slurry consisting of the packin and a deflocculating solvent is poured into the column; t f e bed was formed by sedimentation and then solidified by a flocculating 0003-2700/92/0364-255R$10.00/0

solvent. Shalon (A12) developed a slurry compressor for obtaining a homogeneous, pressurized, packed absorbent bed of slurry in a chromatographic column. The influence of column preparation and particle size of silica on the operating conditions in preparative medium pressure LC (A13) was reported. Five packing methods were tested and two newly elaborated dry-packing procedures, using vacuum and nitrogen overpressure, resulted in best packing. As an alternative to conventional column preparation techniques which use beads, a method based on a chromatographic bed consisting of a compressed gel lug with interconnecting “channels” (A14) was reported. d e gel bed was formed by the olymerization of a monomer solution in the chromatograpiic tube. The resultant polymer chains aggregate into bundles where the voids between them act as channels to allow eluent pass e Several techni ues for coating the inner wall of open-tub& columns for LE (A15-A17) were reported. Column Hardware and Dedgn

Ito and co-workers (A181 developed a chromatography column which contains a dispersion plate on the inlet side before the filter which resulted in increased resolution of the column. A high-pressure column assembly for a liquid chromatyraphy s r t e m was described by America (A19). The design o lar e- iameter columns for preparative liquid chromatograpfy was reported by Cox (A20).A novel HPLC column system was re orted by Ge and Wallace (A21). The systt?mconsisted of a iexible-walled column made of Teflon tubing and a compression chamber through which the eluent was pumped. The system can be useful for characterization or application of new stationary phases which are not commercially available. Malntensnce and Troublerhootlng

A review (A22) examines the heterogeneity of the silica surface and the existence of a low population of strong adsorption sites. Methods of detection and determination of these sites were discussed as well as techni uea for suppreasion of unwanted adsorption activity. Tana%a and co-workers (A23)re rted on the TEM characterizationof HPLC pac m a t e r i g The evaluation of the stability of polymer-coate silica-based packing materials for HPLC was examined by Takeuchi and co-workers (AH). Jinno (A25)used cross-polarization and magic an le spinnin carbon-13 solid-state NMR spectrometry to irkntify the functionality of Cu stationary phases. The NMR method was compared to the retention behavior method for the identification. Jeng and Langer (A26) described the use of hydroquinone oxidation to benzoquinone as a diagnostic reaction for the detection of reactive zones in silica columns for HPLC. Law and coworkers (A27)studied the stability of silica packing materials toward a mixed aqueous-organic eluent at alkaline pH. The stability was found to be excellent with certain types of alkaline eluent. Pfannkoch and co-workers (A28)reported on aluminum ion mediated stabilization of silica-based anionexchange packings to caustic regenerants. The presence of aluminum ions in the caustic wash significantly reduced and in some cases virtually eliminated silica dissolution. The

k”fi

@ 1992 American Chemical Society

255 R

COLUMN LIQUID CHROMATOGRAPHY M h y J. Bahowlck is a graduate student at the University of Washington. He received a B.S. Degree with Honors and Distinction In Chemical Engineering from the University of Wisconson, Madison, WI, in 1982. Ptior to beginning graduate work in 1989, he was a Research Chemist for Appieton Papers Inc. in Appleton, WI, where he was named co-inventor for two patents. His research interests include process analysis and monitoring, chromatographic data analysis, high-speed LC, and the statistical design and analysis of experiments.

Vwavsgu Mwugalah is a graduate student in Analytical Chemistry at the University of Washington. He received a B.S. in Chemistry at the University of Sri Lanka. He worked at the Geological Survey Department of Sri Lanka as a Senior Chemist for 15 years. He was awarded a M.S. from the Imperial College of Science and Technoiogy, University of London, in 1976. He was the Head of the Analytical DMsion at the Institute of Applied Science and Technology, Guyana, from 1984 to 1988. His work I experience includes the analysis of geochemical, environmental, and industrial raw materials. pesticide residues. and food stuffs. His present research interests include method development for automated industrial process analysis, the analysis and characterization of polymers, flow injection analysis, and chromatographic techniques.

'4

Andrew W. Sulya Is a graduate student in Analytical Chemistry at the University of Washington. He received a B.A. in chemistry from Coiby College, Watervilie, ME, in 1988 (Magna Cum Laude). He was awarded a Maine State Government Internship in the Department of Environmental Protection, and has received a Lando-SOH10 Undergraduate Fellowship (1987) at the University of Minnesota, Minneapolis, MN. His honors include the Student Award of the American Institute of Chemists Foundation (1988), the ACS Undergraduate Award in Analytical Chemistry (1987), and election to Phi Beta Kappa Honor Society (1987). His research interests include novel gradient separation and detection techniques for microbore and open-tubular HPLC, muttivariate chemometric data analysis techniques for chromatography, and instrumentation for real-time chemical analysis and poilution prevention. Dank1 B. Taylor is currently a graduate student in Analytical Chemistry at the University of Washington. He received B.S. degrees (Cum Laude) in Chemistry and Physics from Butler University, Indianapolis, IN (1988). He was the 1988 Ringold Fellowship recipient at the Universlty of Washington. His research interests include determination of metal speciation, element specific detection, method development, process control, and on-line analysis.

"t'

-

' -&*

hysical/chemid changes in the column packing which result Kom caustic washing were studied by solid-state NMR and other physical techniques. Verzele and co-workers (A29) reported an elastic inner wall coating in the fused-silica capillaries used for LC on packed fused-silica capillary columns which stabilized the packed bed and thus increased column efficiency and life expectancy. Dolan discussed factors regarding column flushing (A30) and column blockage (A31).

B. INSTRUMENTATION Progress in li uid chromatography instrumentation continues with notaxle advances in the fields of microbore LC, experts s stems, robotics, and rocess chromatography, as evidenKby the multitude of LE applications in these areas. This section of the review will focus on the new developments 256R

ANALYTICAL CHEMISTRY, VOL. 64, NO. 12, JUNE 15, 1992

R M E. Synovec is currently an Assistant Professor of Chemistry at the University of Washington and is an active participant in the Center for Process Analytical Chemistry (CPAC). He received his B.A. in Chemistry (Summa Cum Laude) from Bethel College, St. Paul, MN, In May 1981, and his Ph.D. in Analytical Chemistry from Iowa State University, Ames, IA, under the direction of Edward S. Yeung in August 1986, prior to joining the faculty at the University of Washington. He is a member of the American Chemical Society, Analytical Division. Honors include the Alpha Chi Sigma Graduate Award (1984). an ACS Research Fellowship (1984). a Phillips Petroleum Fellowship (1985-1986), and an Iowa State Excellence in Graduate Research Award (1986). His research interests include developing improved microbore liquid chromatographic separation, detection and quantitation techniques for either bench-top or process analysis, highspeed, high-temperature, and gradient microbore liquid chromatography, applications of lasers and fiber optics to solve detection problems, process control and on-line analysis, and macromolecule separation and detection theory. He has published 38 research papers and holds one patent on these subjects. Rkhard J. Berman is currently the Manager of Applications Development at ALPKEM Corp. He received his B.S. in Chemistry from the University of Minnesota in 1985, his M.S. in Organic Chemistry from the University of Washington in 1987, and his Ph.D. in Analytical Chemistry from the University of Washington in 1990 under the direction of Dr. Gary D. Christian and Dr. Lloyd W. Burgess. The subject of his dissertation research was the development of renewable reagent-based fiber optic chemical sensors. His interests include development of instrumentation and sensors for process and environmental analysis, flow injection analysis, micromachined chemical sensors, and the use of membrane technology in analytical chemistry.

Wb N. R m is currently employed at the ALPKEM Corp. as a research and development chemist for automated flow analyzers. He received a B.S. from the University of Montana (1984) and worked for 2 years as a chemist in the environmental testing industry. He earned his Ph.D. in Analytical Chemistry from the University of Washington in 1991 under the direction of Assistant Professor Robert E. Synovec. He received the Battelle Northwest Fellowship (1989) and the Dow Outstanding Graduate Student Award (1989) while pursuing a Ph.D. at the University of Washington. His research interests include iaser-based detectors for microbore LC, multiwavelength fiber optic detectors for microflow systems (LC and FIA), high-speed and high-temperature LC separation and detection methodology, and instrumentation development of automated flow analyzers for environmental analysis and industrial process monitoring. He has published 14 research papers on these subjects. Edward..I Johnson is currently president of ALPKEM corporation, a manufacturer of continuous flow analyzers. From 1988 until 1990, he served as Technical Director for the Center for Process Analytical Chemistry at the University of Washington in Seattle. WA. He heid a variety of positions during a 10-year period with Dionex Corp. in Sunnyvale, CA. The final position was Vice President of Technology. He sewed as a Senior Applications Chemist with Varian for 2 years, where he coauthored the book f3aslc LlquM Chromatography. As a Senior Research Chemist at Goodyear Tire & Rubber Co. in Akron, OH, he developed more than 100 analytical methods. He has published numerous papers dealing with both liquid and ion chromatography. He was co-inventor for 8 patents. He received a B.S. in Chemistry from the University of Washington in 1964 and a Ph.D. in Analytical Chemistry from Washington State University in 1967.

in column liquid chromatographyhardware, novel hardware implementation, and software developments. Additionally, applications of automation hardware and sohare are included which are of general interest for implementation of the

COLUMN LIQUID CHROMATOGRAPHY

emerging field of LC automation. An excellent review with 121 references of column chromatographic hardware is iven b Berry (BI). A review of LC hardware progress in &e USJR was published by Aleksandrov and Andreev (B2),and a review of microcolumn LC hardware was published by Got? and cvworkers (B3). A review with 58 references conce the smilaritiea between is discussed by Ruzicka LC and flow injection analysis and Christian (B4). An open tubular column liquid chromatograph using silicon chip technology was develo by Manz and co-workers (B5). Monnig and co-workers ( 6 ) designed a packed and open tubular LC s stem for high-s eed LC analysis. Process chromato a p L were designed gy Holzhauer-Rieger and co) Guillemin (Bs).Implementation of on-line workers (f7and HPLC was also shown for both components of a bioreactor by Favre and co-workers (B9). The effect of mobile-phase temperature on LC detector artens (B10). noise was invea ' ated was by Paeeen and H Schneider and itt (B11)described a c a p y ap aratus capable of coolin the eluent before entering a LC etector and heatin the efuent before entering the column. The use of thermmtectric elements for tem erature control of LC columns was reported by Tyrefors pB12) and Sanders and Craft (B13).

(a

IP

%

B

Solvent CondBonlng/Pumps/Gradlent Devices

On-line mobile-phase degassing modules were developed for LC b Shirato and co-workers (B14) and Stubba (B15). Eberhariand co-workers designed a low-cost helium spaqer and solvent delivery s stem for LC (B16). A high-purity solvent generator was eveloped by Dasgupta (B17)and coworkers wing a perm-selective ion-exchange membrane. Miller and Shafer (B18)developed a s stem for testin the stability of pumping hardware for L e and reportecf the maximum and minimum flow rates, while Sheehan and Schachterle (B19) describe tests easil performed in any lab for evaluating the performance of L pumping systems. A liquid check valve utilizing sintered ceramic material was reported by Ledtje and Lon (B20) to reduce sticking with acetonitrile water mixtures. h e r and Nagel (B21) reported on a novel iquid piston pump employing two pistons 180' out of phase to deliver a constant ca acity. Bruin and coworkers (B22) re rted on electrically given open tubular LC with s u b s t a n t i 8 better separation efficiency than pressure-driven separations. Pfeffer and Yeung 0323) demonstrated the use of electroosmotic flow for open tubular LC se aration of neutral, geometrical,and positional isomers with efEciencies of up to 230 OOO plates on a 54-cm column in less than 4 min. A membrane ump with sufficient flow and reseure specifications for d L C was reported by Obst (BZa). fames (B25) described a reciprocating piston pump with a novel dual-seal configuration to increase the life of the seals. A novel HPLC ump exhibiting high flow stability was described by L e B k c (B26). A dedicated micro-HPLC radient system for packed caillary LC was evaluated by krisciani and Andreolini (B27, 528).Hue and Siouffi (B29) presented a review of computer-assisted optimization for gradient elution HPLC. A novel gradient elution system for microcolumn LC utilizing step adienta with a multiple-loop valve waa demonstrated by &nka and Novotny (B30). A packed-bed gradient generator was designed by Munk (B31) to operate on the low or high pressure side of an HPLC pump. Berry and co-workers (B32) used a fused-silica open tube to generate S-shaped microgradients. A gradient delivery system for microbore and open tubular LC was reported by Bauer (B33).

i

E

i

I njectlon

An evaluation of two injections systems for open tubular LC is presented by Claemsens and co-workers (B34). A novel injection system suitable for correlation chromatography was reported by Mars and Smit (B35),who furthe? reported the development of an electrochemical concentration modulator as an injection device (B36) for correlation chromatography. Evans and McGuffin (B37) directly examined the effect of the injection solvent on the zone profiie by placing a detector before a packed bed column and at five positions on the

column. A system for transmitting fluids from high-pressure to low-pressure environments suitable for LC was described by Nickerson and co-workers (B38).Debets and co-workers (B39) describe a zone-electrophoretic sample pretreatment coupled on-line to LC with detection limits similar to direct injection. Solid injection was applied to insoluble sam les for preparative chromatograph b Miller and co-worfer8 (B40). Pavlik and co-workers (i417 described the use of an optical sensor to detect complete loading of an injection valve with subsequent injection controlled by the optical sensor. A novel fluid seal was reported b Sgourakes and Koziol (B42) to be suitable for injection v d e applications in HPLC. Automation/Sample Prep

On-line flow extraction, preconcentration, and LC se aration were reported by Halvax and co-workers (B43). DefMar and Hemberger (B44) reported the use of polyethylene and polypropylene tubin for preconcentration of organics from groundwater followefby an appropriate solvent to release the organics for injection into a LC system. Haginaka and Wakai (B45)used a hollow-fiber membrane reactor and column switching for automated derivatization of amino acids. Several automated diluters were reported (B46-B48). Membrane technology was employed in the food industry (B49, B50), clinical industry (B51),and environmental analysis (B52)for automated sample cleanup. Similarly, automated solid-phase extraction was used for sample prep (B53-B55). Simon and co-workers (B56)used a wet effluent denuder coupled on-line with a LC system for trace analysis of atmospheric SO2. Method OptimlratlonlExpert System

A review was presented by Brereton (B57)on chemometric LC separation optimization. Haddad and Sosimenko (B58) reviewed computer optimization of LC separations. A review with 25 references was presented by Kenney (B59)on the use of expert systems for roc= control. A comparison of ex rt system tools for HPEC was given by Van Leeuwen an coworkers (B60). Warren and co-workers (B61) demonstrated the use of mapping strategies for eluent optimization in LC. Fully automated o timization pro rams were described by Rooney and co-worIers (B62) and 8jord'evic and co-workers (B63). Jinno and co-workers (B64) and &II and co-workers (B65)developed computer-assisted method evelopment and data analysis systems. Tsuji and Jenkins (B66) developed a knowledge-based expert system utilizing facts, heuristics, and problem-solving strategies for trouble shooting 21 common LC separations. Matsuda and Hayashi (B67, B68) presented two papers on information theory based optimization methods.

8"

Robotics

A review of laboratory robotics with 42 references was resented by Felder (B69). A robotics system was modified Ey Russell and Boyd (B70)for dual LC injection of dissolution samples. Lloyd and Lang (B71) compared accuracy and recision of robotics versus manual preparation for LC. botic sample preparation and analysis of peanut butter for aflatoxins was presented by Pieta (B72). A robotics sample preparation system employing an expert control system was reported by Kin ton and co-workers (B73). Robotic sample preparation and FC analysis of clinical samples for nefazodone (B74),diclofenac (B75),SC-4711 (a new antibacterial (B76)), and automated extraction of bis(2-ethylhexyl) phthalate (B77) were reported. Robotic sample prep and LC analysis of harmaceuticals was reported by Kanczewski and co-workers B78). A fully automated exopeptidase digestion and peptide/protein sequence analysis was reported by Thoma and Crimmins (B79).

L

P

C. DETECTORS General Introduction. The fundamental work in LC detection continues to be geared toward dealin with the physical constraints imposed b microbore and capillary separation methods. For optical Jetectors such as absorbance detection, this implies new detection ideas that maximize sensitivity while minimizing detector band broadening. Also, several pa ers dealt with work directed toward minimizing optically Ltected artifacts due to refractive index changes ANALYTICAL CHEMISTRY, VOL. 64, NO. 12, JUNE 15, 1992

257R


that occur during gradient elution in both microbore and ca illary LC. A significant increase in LC/MS for ca ill L8was also observed. Another focus in f u n d a m e n d w z in LC detedion is the development of detectors and detection methods that provide added selectivity. Accordmgly, several fundamental papers in the areas of chemiluminescence, optical activity, and infrared detection have warranted a separate section for each, while in previous reviews these detectors were discussed in the Miscellaneous Detectors section: Thus, the review on detectors has two groups, roughly divided on the basis of apparent developmental activity on each detector. Detectors with more substantial developmental activity are discussed in alphabetical order: Absorbance, Chemiluminescence,Electrochemical,Fluorescence, Indirect Detection, Infrared, Mass Spectrometry, Optical Activity, and Refractive Index. Following these sections is a section on Miscellaneous Detectors. In a review by Yeun (CI),two recently developed approaches for sensitive aisorbance detection in capillary LC and capillary electrophoresis were described. The first approach involved irradiation down the axis to gain a significant improvement in sensitivity. The second approach involved an energy transfer from absorbing anal s to a fluorophore added to the mobile phase, with su sequent secondary emission improving detection limits for the analyte. The use of laser-based detectors in LC was reviewed by Berthod (C2). The review, with 29 references, discussed LC detector requirements, relevant laser properties, and several examples of laser-LC combinations involving light scattering, fluorescence, photoionization, photothermal, refractive index, optical activity, and hotoacoustic detectors. In a related review by Belen'kii (C37,capillary LC with laser-based detectors was characterized in terms of concentration sensitivlty and ultralow volume detection capability. The popularit of ion chromatograph (IC) has led to no(C5).The former table reviews by 6asgupta (C4)and Roc& was a review of 170 references on postcolumn manipulation in IC for improvin the selectivity and sensitivity for the detection of an ana&te or class of analytes (C4).The latter was a review of 36 references comDarine different detector types for IC (C5). A review b Synovec (C6)described new absorbance and refractive indYex eradient detectors desimed for Drocess LC. The detectors w&e designed to function-under mire difficult conditions than labtop instruments, yet provide comparable or improved performance.

P

D. ABSORBANCE DETECTORS In general, absorbance detection is following the latest trends in liquid chromatography separation instrumentation; for example, the growth of microbore, packed capillary, and open tubular HPLC has produced a trend toward the miniaturization of absorbance detector flow cells to reduce detector band broadening. The primary emphasis of this review section, hence, is to report on the fundamental developments in UV-vis absorbance detector instrumentation; therefore, ublications of novel separation methods that apply absorL c e detection will not be included in this review. Also,trade journal articles about commercially available absorbance detectors have been excluded because fundamental developments in these instruments may be referenced in patents and/or manuscripts. This section does include review papers on absorbance detection, detectors for novel separation techniques, theoretical and experimental investigations of absorbance flow cells, instrumental calibration techniques and finall novel hardware for postcolumn reaction. Reviews on absoriance instrumentation were limited to two. A review of principles and instrumentation of diode array detection was written by Huber and Fiedler (01).Jones (02)surveyed work on two new UV light sources driven by "Sr and radioluminescence according to the phenomenon of Cerenkov radiation. Novel separation approaches have been the drivin force for new absorbance detection schemes. Gonnord and biouffi (03)have studied two-dimensional column chromatography, in which a mixture is eluted by two different solvents in orthogonal directions along a square, thin column and eluted through a slit that acts as the detector cell. A photodiode array is placed parallel to the slit to continuously monitor the UV absorption of analyte bands spread along the column width. 258R


Xi and Yeung (04)demonstrated axial-beam, on-column absorption detection for open tubular capillary liquid chromatogra hy. Using the capillary column as an optical waveguide,e!t authors were able to cou le light down the entire length of the column to utilize the Lll length of the sample bands as the path length for absorbance measurements, thus producing improvements in the concentration limit of detection. Synovec and Renn ( 0 5 ) have developed a single optical fiber multiwavelength absorbance spectrophotometer that incorporates a position-sensitive detector to correct for light source fluctuations and refractive index (RI) aberrations. Synovec, Renn, and Moore (06)have reported 1 X lo4 au detection limit with this spectrophotometer when it was applied to high-temperature HPLC (150 "C). Solarization of the fiber o tic in the UV range was evaluated, and precautions were empiasized. Theoretical relationships were derived by to relate changes in the RI of the Renn and Synovec (07) mobile phase to aperture-limited absorbance measurements as ap lied to the single fiber optic two-wavelength detector. The fetection method virtually eliminated baseline drift associated with thermal-induced RI aberrations during thermal gradient (ambient to 150 "C) microbore liquid chromatogra hy as well as during mobile-phase gradients and other low methods like flow injection analysis. Sulya, Moore, and Synovec (08)demonstrated that the detector's successful real-time RI correction is an improved detection method for performing on-column preconcentration of samples under noneluting conditions followed by either mobilephase gradient or thermal gradient elution. In related work, a theoretical model of the RI artifacts associated with absorbance detection in a Z-pattern flow cell during rapid changes in solvent composition was proposed by Evans and McGuffin (09). Several other theoretical and experimental investigations of flow cells were performed with emphasis on miniaturization and sensitivit Sug ested guidelines for absorbance measurements in ked-sifica capillaries were sug ested by Bruin et al. (DIO) after theoretical and experimenta! studies of flow cell design and resulting sensitivity, noise, linearity, band broadening, and refractive index effects. They reported that a focusing lens in front of the capillary resulted in a higher sensitivity and linear range than a cell with an adjustable aperture width. A U-cell design produced a longer longitudinal light path and an increased signal-to-noise ratio. Chervet et al. ( D l l ) constructed a flow cell for capillary LC and su ercritical fluid chromatography with a path length of nearyy 2 cm and a volume less than 90 nL. This design showed improvements in sensitivity of 100-500 times as compared to on-column detection. Tsuda and Kobayashi (012)achieved a 10-fold increase in sensitivity by using a cylindrical lens to obtain a redangular light beam that more closely matches the cross-sectional shape of a cylindrical flow cell in capillary LC. The flow profile and band-broadening in a 0.6-pL micro flow cell at different flow rates was calculated theoretically using finite-element analysis by Kamahori et al. (013). Band due to both mixing and laminar flow was studied % % !,:?l and results compared favorably to experimental work. De Andrade et al. (014)described a versatile, modular flow cell with interchangeable units of different dimensions and optical fiber bundles for analytical and preparative scale LC as well as for flow injection analysis. A miniaturized detector cell by Venele et al. (015)allowed adaptation of two commercial diode array detectors to micro liquid chromatography. Several methods for wavelength optimization and calibration of multiwavelength absorbance detectors were investigated. A rocedure for determining the wavelen h accuracy of a variagle-wavelength detector was patented y Esquivel (016).After a flow cell is filled with a calibration solution of Tb(II1) ions in pro anol, the wavelength of maximum absorbance is found antcompared to the actual wavelength of maximum absorbance as obtained from a reference spectrum. used The difference is then calculated. Binder et al. (017) wavelength ratios during dru detection to calibrate a multiwavelength detector and ev8uate intrument-to-instrument variation in a series of detectors. This information, as well as the second derivative zero intercept for the drug spectra, was used to apply successfully UV spectral libraries from different instruments. Bogusz and Wu (018)also reported a correction procedure for the interlab use of spectral libraries. Using a type of information theory called function of mutual

f


information (FUMI), Ha ashi and Matsuda (019,020)determined the optimum Jetection wavelength in an HPLC method as well as the o timum amount of internal standard. Studies by Jandera a n i Prokes (D21)showed that errors in o h i z i n g the wavelength of maximumabsorbance had a large e fect on sensitivity while operating at less than optimum s ctral bandwidth and data collection rate had little effect. hey also described the collection of repeated high-speed chromato a m 8 to enhance sensitivity and detection limits. Carr and &an (022)stated that most commercially available diode array detectors do not realize low-level peak inhomoeneities. They performed statistical F-tests and t-tests to ietect peak inhomogeneities with a high level of confidence ) patented a spectrochemicalanalys& Finally, Blaffert (023has device for HPLC separations which uses an evaluation circuit device that collects a matrix of spectral values for an eluted substance and determines the concentration of the substance by a single scan of the data matrix through an evaluation. The device also calculates the concentration of the carrier substance. Improved postcolumn instrumentation for derivatization and other detection schemes was reported. Wolf and Schmid (024)added an on-line photoreactor for the irradiation of barbiturates with UV li ht to produce a photochemical reaction that creates a bat!ochromic shift in the anal s and a strong spectral band at 270 nm. Stereoselective etection of L- and D-amino acids was performed by Dominguez et al. (0%) usin? two on-line immobilized enzyme reactors. The first contam either L- or D-amino acid oxidase to produce hydrogen peroxide which then reacts at another reactor containin horseradish peroxidase, to produce a colored compount! which is detected spectrophotometrically. LeonGonzalez and Townshend (026)reported the determination of carbamate and organophosphorus pesticides b spectrophotometrically monitoring the activity of acetylchoLesterase enzyme that is immobilized on controlled pore glass in a minicolumn. The system incor orates a conventional flow in'ection analysis (FIA) assemb y. FIA was also coupled to HbLC by Baba et al. (027),for the spectrophotometric detection of H- hosphonates. In coupling counter-current chromatograpiy and photodiode array detection, Schaufelused a postcolumn reactor to add an auxiliary berger (028) solvent that reduced the detector noise caused by nonretained stationary phase. Turbidity from thermolabile mobile phases in counter-current chromatography makes UV monitoring difficult. This problem was resolved by Oka and Ito (0291, who inserted a 3-m-long Teflon tube with an inner diameter of 0.46 mm between the column and the detector and thermostated the tube in a water bath at 30 "C. A similar tube was applied at the detector outlet to suppress gas bubble formation.

r

F

P

P

E. CHEMILUMINESCENCE DETECTORS Chemiluminescence (CL) detection in liquid chromatography has received increasing research efforts as a result of the excellent sensitivity and selectivity of this technique. For example, several authors have reported detection limits superior to fluorescence determinations. This section of fundamental work in CL detection includes reviews written on the subject of CL detection in HPLC, novel instrumentation for CL, fundamental studies of photolysis coupled with CL, new solid-phase and immobilized re ents and instrumentation, and a study of the solubility of L reagents in a typical HPLC mobile p k . In general, fundamental studies of other r q e n t s and applications of exist' CL techniques have been omitted because these will be i 3 u d e d in other reviews. The interest in chemiluminescencedetection is exemplified b the many reviews dedicated to the subject. Nieman (El, wrote two reviews, one with 90 references the other with 156, describin several solution-phase on-line detection schemes for HP&C and flow in'ection analysis (FIA). Fujiwara and Kumamaru (33) reported 65 references dealing with CL detection of several separation techniques, including HPLC, electrolysis, solvent extraction, membrane separation, and FIA to name a few. A review with 99 references was written by Townshend (E41concerning recent ap roaches for monitorin CL in FIA and HPLC, including apptcations of luminol and peroxyoxalate CL, as well as applications where the luminescence results directly from the analyte. Imai (E5)has

7

A)

summarized reagent types, analytes, and detection limits for CL in HPLC in a review that contains 133 references. Givens et al. (E6)have reviewed the specific CL research of oxidation of oxalic esters with hydrogen peroxide. This work describes in depth work to improve the CL efficiency and to enhance the selectivity for target analytes. A kinetic model for maximum light production was based on the effects of catalysts, reagents, and reaction conditions and applied to HPLC thro h the time-dependent emission window concept. A book editey by Birks (E7)contains several subsections on CL detection in HPLC. A chapter written by Poulsen and Birks ( E n , containing 39 references, is concerned with the reaction variables that might influence the a lication of peroxyoxalate CL to trace chemical analysis in &LC and FIA. Another chapter discusses existing and proposed methods of CL detection in HPLC and gas chromatography, that utilize singlet oxygen mediated processes to improve sensitivity. Several developments in instrumentation for CL were reported. Schreurs et al. (E81applied time-resolved detection with a pulsed Xe lamp and a gated photomultiplier to detect 4-maleimidylsalicylic acid-labeled analytes that reacted with Tb(II1) to roduce a long luminescence decay time (>0.1 ms). Chang anlTaylor (E91developed a sulfur-selective CL detector for packed-capillary column HPLC that is based u on the decomposition of sulfur-containing analytes in a hy8rogen air flame. The analytes decompose into sulfur monoxide an react with ozone, thus creating CL. Optimization of the flame, which was dependent upon the mobile phase used, provided a detection limit of 4 pg of sulfur using 50/50 water/methanol as the mobile hase. Jalkian, Ratzlaff, and Denton (EIO)demonstrated t i e usefulness of a solid-state two-dimensional charge-coupled device (CCD) for CL detection of Co2+,Cu2+,Cr3+,and H 02. Outstanding dynamic range was accomplished by appfying simultaneous variable binning to measure the transient light emission. Baeyens et al. (Ell)studied reagent concentration, pumping systems, flow rate, and extracolumn band broadening to achieve detection limits of 200 fmol of dansylated amino acid as measured by peroxyoxalate CL. A 100-pm inner diameter fused-silica caillary tube was connected to the end-frit of a reversed-phase ! IPLC column to bring the column eluate to a mixing tee to allow reagents to mix as they entered the 74-pL flow cell. Similarly,the optimization of 14 parameters for peroxyoxalate CL detection of derivatized fatty acids was completed by Hanaoka (E121by incorporating results from other published work. The performance of a modified spectrofluorometer for CL detection was evaluated by Jones et al. (E131 to develop a novel method for trace metals. Metals se arated by ion chromatuyphytdisplace cobalt from a Co-EDkA postcolumn reagent he h rated cobalt is detected by luminol-peroxide CL. Detection limits ranged between 2 and 100 pg/L. Poulsen and Birks (E14)reported the optimization of a postcolumn photolysis/CL detector for quinone molecules. The quinone analytes sensitize the photooxidation of the mobile phase to produce hydrogen peroxide which is detected by peroxyoxalate CL. Kwakman et al. (E15)re orted postcolumn photolysis of dansylated derivatives of &l-, nitre and chlorophenola to produce products that may be sensitiveli detected by peroxyoxalate chemiluminescence. Detection limits of about 0.01-0.1 ng/mL have been achieved. Novel solid-phase and immobilized reagent systems for CL detection have been reported. Aichin er et al. (E16)used a short reaction column packed with bisf2,4,6-trichlorophenyl) oxalate and a quartz flow cell containing aminofluoranthene immobilized on glass beads. Such a system is applicable for the detection of a variety of compounds of pharmaceutical interest that exhibit low UV absorbance. Kawasaki et al. (El7) reported an immobilized acyl-CoA synthetaseacyl CoA oxidase s stem coupled with CL detection of the hydrogen peroxiL catalyzed by microperoxidase. The technique was illustrated with the detection of fatty acids without an labeling procedures. Bile acids were determined by Maeia et al. ( E M )usin a ostcolumn reactor with immobilized 3ahydroxysteroidid e l drogenase that generated NADH, which was then detected gy CL. The detection limit was about 2 pmol for each bile acid. To improve the solubility of peroxyoxalate CL reagents in loxy moiety were acetonitrile, eight aryl oxalates having an studied by Nakashima et al. (E19). Besi e8 solubility, CL intensities and lifetimes were compared.

d

9


259R


F. ELECTROCHEMICAL DETECTORS This section is arranged as follows: Reviews and Comparative Studies, New Detectors, New Electrodes, Novel Electrochemical Applications, and Conductivity Detection. The interest in electrochemical detection appears to have remained relatively constant, although there is increased interest in modified electrodes. Revlews and Comparatlve Studles

Two very extensive reviews on the various electrochemical detectors used for ion chromatograph were prepared by Jandik, Haddad, and Sturrock ( F I ) andlHorvai and Pungor (F2). A review by Barisci and Wallace (F3) focused on the key factors of electrode material, cell design, and the specific measuring technique. Pulsed amperometry for the detection of nonelectroactive materials was reviewed by Austin-Harrison and Johnson (F4). The common misconceptions such as choice of mobile phase, reference electrode, and detection of uncharged analytes was discussed by Kissinger (8’5). Several reviews dealt with electrochemical detection and HPLC (F6-F9). There has been much research into using the selectivity of enzymes and chemically modified electrodes to yield highly specific detection schemes. A very extensive review of this work was published by Gorton et al. (FIO). The use of derivatization to impart electrpchemical sensitivity was reviewed bv Lunte (F11).A studv of the use of amwrometrv with capillby liquid chiomatogriphy was given by Ruban e‘t al. (F12). New Detectors

More work on utilizing multiple electrodes and arrays has been re orted during this review period. The use of different electrote materials in the arra was reported by Hoogvliet and co-workers (F13). Sturroci has applied factor analysis to his swept-potential technique to determine the presence of coeluting components (F14). A novel detector using eight working electrodes in a wall-jet design was reported (FI5). In a series of pa ers (F16, F17)Ramstad and co-workers have reported on eEctrosorptive techniques that have shown good potential in both ion and liquid chromato aphy. They have shown detection based on differential doubElayer capacitance has the most general a plicability. Ruban (FI8)re orted on a ‘cylinder-in-flow” c e i design for amperometry. A)low-cost carbon wire amperometric flow-through detedor was described by Yang (F19). A novel microband thin-la er flow cell with a volume of 5 pL and a flow rate-independkt response has been reported by Kuwana and co-workers (F20). Another cell design em loying either carbon or gold fibers has also been reported &21). In attempts to obtain greater selectivity, Connor and co-workers have described detectors utilizin tissues and microbes (F22). Nagels and co-workers describej a wall-jet detector that can be easily operated in either a convection/diffusion or a diffusion-controlledmode (F23). A novel electrode-se arated piezoelectric quartz crystal detector has been describei (F24).A detector capable of simultaneous UV-visible detection and amperometry was described by Nagy and Anderson (F25).Two papers discussed the potential of electrokineticdetection in liquid chromatography (F26,F27). New Electrodes

A comparison of an interdigitated-microarrayelectrode and a single-potential-microarray electrode has been reported (F28). Wi htman et al. (F29) reviewed the potential of microelectrofes for probing spatially heterogeneous concentrations. Theoretical and experimental data were reported for circular electrodes used in both steady-state flow and liquid chromatography conditions (F30). Johnson and LaCourse reviewed the use of pulsed techniques at both platinum and gold electrodes (F31). Stojanovic and co-workers have shown that microelectrodes lack the sensitivity to detect arsenic in bottled water when compared to conventional size electrodes (F32). It has been reported (3’33)that a Ag/AgBr electrode exhibits excellent sensitivity for a wide range of anions separated by ion chromatography. Two papers reported on the use of mercury electrodes in liquid chromatogra hy (F34,F35). A comparative study of Pt, Au, Cu, Ni, Ag, anfCo electrodes for the detection of carbohydrates and amino acids was re26OR

*


ported (F36). Several pa ers reported on various aspects of carbon-fiber electrodes ($3374’40). A lar e number of papers reported on chemically modified electrofies. Baldwin and Thomsen (F41) reviewed many of the recent trends, and Wang et al. (F42) also discussed several applications in both liquid chromatography and flow injection analysis. Gunasingham et al. (8’43) reported on attempts to gain selectivity by using composite electrodes made b dispersing platinum particles into a cation-exchange p o k e r coated onto glassy carbon. Glassy carbon was a popular substrate for many chemically modified electrodes. Nickelbase-activated (F45)alumina (F46), modified carbon (F44), and polymeric cobalt phthalocyanine (F47) lassy-carbon electrodes were reported. Zhou and Wang ( F A reported on the use of a cop er-based chemically modified electrode. Nickel or cupric iexacyanoferrate films were described for the detection of group 1A and ammonium ions (F49).Electrodes formed from mixtures of Kel-F and graphite (3’50)and carbon paste (F51)were described. Nafion was employed in several studies (F52-F54). Novel Electrochemlcal Appllcatlons

LaCourse and Johnson (F55)described the mechanism of

ulsed amperometric detection for carbohydrates. Barisci and

ballace (F56)evaluated flow-through photochemical reactors combined with electrochemical detection. Derivatization to permit electrochemical detection was reviewed by Lisman and co-workers (F57).A review discussing the use of immobilized enzymes and amperometric detection with emphasis on its advantages has been ublished (F58).The determination of amino acids as their tansy1 derivatives using electrochemical detection was discussed (F59). Clos and Dorsey reported on the use of surfactants to reduce or prevent adsorptive fouling of glass-carbon electrodes (F60). Conductlvlty Detectlon

Berglund and Dasgupta (F61) reported on a novel twodimensional conductivity technique that permits enhanced sensitivity for weak acids. The use of membranes and electrochemical techniques to generate the eluent for ion chromatography was reported by Dasgupta and co-workers (F62). A uni ue miniature three-electrode flow cell was designed to provije simultaneous potentiometric and conductivity measurements (F63). A similar paper described simultaneous conductivity and UV detection (F64).Two papers discussed the theoretical aspects of suppressed conductivity detection (F65, F66).

G. FLUORESCENCE DETECTORS In LC, fluorescence detectors are often preferred for trace analytical studies because of their good selectivity and excellent sensitivity. This section of the review considers publications and review articles on LC fluorometric detedor instrumentation and techniques. Routine applications of fluorescence detection have been omitted. Also, an chemiluminescence techniques that may use fluorometric dretectors can be found under “Chemiluminescence Detectors”. The majority of the pa ers ublished durin the past 2 years dealt with the laser-infucef fluorescence &IF). Comprehensive reviews of the principles and applications of LIF as a detection mode in LC were given by Van den Beld and Lingeman (GI) and Lingeman et al. (G2). Lin eman’s review (G2)outlined the principles of LIF and off,IF-LC instrumentation. The review focused on a proaches that extend ap licability, such as frequency douf ling, variablewavelengd dye lasers, and derivatization. Two-photon excitation and time-resolved fluorescence also were considered. Lingeman et al. (G3)reviewed the fluorescence detection in LC and discussed the improvement of selectivity for fluorescence detection and chemiluminescence in LC. The hi h-photon flux and the excellent spatial resolution provided %ythe lasers enhance the sensitivity and selectivity of fluorescence detection over that obtained with conventional broad-band li ht sources. Van de Nesse et al. (G4)employed a frequency-joubled argon ion laser for LIF detection in conventional-size column LC. The authors found that shorter-wavelength excitation (257 nm) not only offered the advantage to excite a wide variety of analytes but also elim-


inated the interference of Raman scatter of the eluent. Van de Nesse et al. (G5)combined the frequency-doubled argon ion laser with an intensified linear diode array detector to enable on-the-fly identification by LIF in conventional-size column LC. The technique is suited for trace-level analysis of complex mixtures. Van de Nesse et al. (G6) used an excimer-pumped (XeCl) dye laser to study two-photon excited fluorescence detection in conventiona-sizeLC with aromatic compounds as test solutes and compared the detector with one- hoton fluorescenceunder exactly the same experimental con&ions. In spite of less efficient excitation of the twophoton excitation technique, a detection limit of as low as 1.0 nM was obtained for the dye 4,4’-diphenylstilbene. Novel methods of separation and detection for microcolumn LC using a copper-va or two-photon excited fluorescence detection was descriied by Pfeffer (G7). Yeung et al. (G8)used laser-excited fluorescence detection with micellar electrokinetic chromatogra hy (MEKC) to determine nucleotides at the 6 X lo-’* morlevel. On-column detection with the capabilit of performing multiwavelength pro amming was used by 6 n et al. (G9)for the separation of Lsyl-amino acids by MlfKC. Tsunoda et al. (G10)tested two types of fiber optic-based flow cells: a “Yeun type” cell and a windowless solution droplet type cell wit[-time-resolved LIF in conjunction wih microbore LC. The system was applied to the detection of subfemtomole amounts of some 2,3-dioxonaphthalene-derivatized amino acids. The first use of a multifrequency, phase-modulation spectrofluorometer for fluorescence lifetime determinations on the fly in LC was described by Cobb and McGown (G11, G12). The basis of phase-modulation fluorescence lifetime determinations is the use of a continuous excitation beam that consists of a high-frequency component superimposed on a steady-state component. The fluorescence response is modulated at the same frequency, but is phase-shifted and demodulated as a function of the fluorescence lifetime of the sample. Advantages of frequency-domain,phasemodulation determinations over time-domain, pulsed-excitation approaches were highlighted. Mastenbroek et al. ((313)utilized Sh ol’skii fluorometry as an independent identification methot! to upgrade routine HPLC analysis of polycyclic aromatic hydrocarbons (PAH) in marine sediment samples. The low-temperature Shpol’skii technique provided a high-resolution fluorescence spectra of PAHs that can serve as fingerprints. Zhao and Quan (G14) combined a synchronous fluorescence technique with HPLC for identification of PAHs in urine samples from smokers. A novel a proach for fluorescence enhancement of carbon-centere8 free radicals trapped in water soluble amino nitroxide was the conversion to a diamagnetic product by derivatizing the tra ped adducts with fluorescamine. Kieber and Blough (G1.5816)detected an array of photochemically produced radicals in a variety of water samples by the separation of adducts with RP-HPLC. The detection limit for individual adducts at the subnanomolar level is 2-3 orders of magnitude lower than those of current detection limits, employing electron spin resonance detection. A competitive-bindingapproach in the development of LC postcolumn reactions was re orted by Przyjazny and Bachas (G17).Biotin in vitamin tatlets was determined by the decrease in fluorescence when the effluent from LC column meets a reagent stream containing the binder avidin which was complexed with the fluorescent probe, 2-aminonaphthalene-6-sulfonic acid. Wegrzyn et al. ((718)develo ed a compact unintensified photodiode array-based multicKanne1fluorescence detector for use as a HPLC detector. A unique feature of this detector is the use of a xenon capillary h h l a m p as an excitation source which provides low heat radiation, while still providing a high-intensity continuous spectrum. Cecil et al. (Gl9,G20) used an intensified diode-array detector to evaluate the caabilities of the full fluorescence spectral detection in LC. The imit of detection and linear dynamic r e were determined for the test compounds. The data anyysis methods used included Kalman filter-based methods for adaptive subtraction of background responses, shift correction, and linear regression analysis of overlapped responses. The use of lasers as the excitation source is very suitable for a microcell detector in microcolumn LC, because the beam

P

can be focused onto a very small area with hi h intensity. Tsuda and Noda (G21)examined the effect of t i e geometric position of the laser beam on the capillary cell on the noise from acatterin of the laser light from the cell walls by reflection and refraction. The authors used a video camera to set the laser beam on the ca illary cell. They found that the position of the spot of the faser beam is important for obtaining a good signal-to-noise ratio. With the o timum geometric arran ement, 1.3 fmol of the 4-(bromoetIyl)-7-methoxycumarin ierivative of caproic acid was detected at a signal-to-noise ratio of 5. Takeuchi et al. (G22)examined the effects of the cell structure on the mass detection limits in fluorometric detection in microbore LC. The authors found that noise due to the scatter of the light by reflection or refraction from the cylindrical flow cell wall could be effectively prevented from entering the photomuliplier by either tiltin the flow cell or using appropriate cutoff filters. Jallian and Denton (G23)used a solid-state two-dimensional charge-coupled device to integrate the native fluorescence emission of polycyclic aromatic compounds. This new technique, when ap lied to one-dimensional spectroscopy leads to increased ynamic range. The authors obtained excellent linearity and limits of detection for several priority pollutants. Further, the authors applied synchronous and derivative techniques to the two-dimensional fluorescence data to resolve overlap ing peaks. Pate1 et al. (G247constructed and optimized a postcolumn photolysis/fluorescence detector and extensively examined several classes of nitrogenous pharmaceuticals usin two approaches for generation of fluorescence: (a) UV pfiotolysis followed by the reaction with o-phthalaldehyde-2-mercaptoethanol re ent; (b) UV photolysis alone. The authors found that w i t h x e use of suitable solvent systems and a hotosensitizer and optimization of all experimental cond%ions, many pharmaceutical compounds can be transformed into fluorescing products and achieve nanogram level detection limits. Mawatari et al. (G25)also irradiated the column effluent with UV light to give fluorescence and detected isoniazid and its acetyl derivatives at the nanogram level. Fluorescence linenarrowing spectrcwcopy is a technique that makes use of laser excitation of molecules in low-temperature solid matrixes to obtain vibrationally resolved fluorescence spectra. Hofstraat et al. (G26)developed a new and highly sensitive detection technique based on fluorescence linenarrowing spectroscopy for thin-layer chromatography (TLC) and LC. The authors demonstrated that TLC plates can be used as buffer-memory for LC. The stored chromatogram can be cooled and subsequently probed with the laser beam. Strojek et al. (G27)demonstrated the concept of TLC “Chem Diskette” whereby HPLC effluents are delivered and stored along a linear path on a TLC alumina surface. After removal of the LC solvent, the adsorbed analytes on the TLC surface were interrogated by retracing the pattern with the He-Cd laser irradiation as carried by the optical fiber on the pen holder. Detection limits in the low femtomole range for derivatized amino acids were reported. Packed reactors with immobilized enzymes offer the selectivity of enzymic reactions and the economy gained by immobilizing the often costly catalysts. Kiba et al. ( G B ) immobilized sorbitol dehydrogenase chemically on polyvinyl alcohol beads and used it in a column reactor in a LC system for the specific detection of selected sugars. The NADH produced from the enz ic reaction was monitored spectrofluorometrically. ~ ” o K e d enzyme reactor column can also simplify LC system. Kurth et al. (G29)immobilized horseradish peroxidase on controlled-pore glass and used it for the determination of hydrophilic organic peroxides.

a

H. INDIRECT DETECTION When the desired analytes possess low sensitivity to the detection mode (absorbance, fluorescence, conductivity etc.) being employed, use of a mobile phase or mobile-phase additive possessing a detector response, often called a visualizing agent, will often give satisfactory results. The analytes are indirectly detected by the change in background signal of the visualizing agent when the analytes displace the visualizing agent from the mobile phaae according to defiite mechanisms such as conservation of charge, ion pairing or volume displacement, or whenever the injected analytes compete with ANALYTICAL CHEMISTRY, VOL. 64, NO. 12, JUNE 15, 1992

261 R

COLUMN LIQUID CHROMATWAPHY

or perturb the equilibrium of the visualizing agent between the mobile and stationary phases. Yeun and Kuhr (HI) reviewed indirect fluorometric and electrocfemical detection in capillary LC and capillary zone reviewed photothermal techelectrophoresis. Morris (H2) niques for LC, TLC and FTIR, in which refractive index changes caused by light absorption and ensuing heat evolution are measured. Several instrumentation develo menta for indirect detection were reported. Rice, Thorne, anBBobbitt (H3)demonstrated indirect photothermal detection for microcolumn HPLC using a pump-probe differential thermal lens spectrometer that minimized the influence of the background signal. Pfeffer prepared open t u b e capillary cp!umns by and Yeung (H4) cross-linking vinyl silicone gums inside of fused-silica capillaries. Following reversed-phase or anion-exchange chromatography, laser-based indirect fluorometric detection provided detectable concentrations in the 30 nM range for alcohols and common anions, respectively. Winefordner and co-workers (H5) constructed a low-noise indirect photometric detector employin a highly stable light-emitting diode as the light source an! methylene blue as the visualizii agent. Obrezkov et al. (H6) reported a new ‘kinetic detector” for ion chromatography which, when coupled with a conventional conductometric detector, allows simultaneous determination of weak and strong inorganic acid anions. The kinetic detector use8 the degradation of KBr03 in HCl, catalyzed by reducing anions (especially sulfur containing anions), as the kinetic indicator reaction. This reaction diminishes the background absorbance of the methyl orange reagent. A number of studies of visualization agents for indirect detection included theoretical aspecta of detection or compared invesindirect detection modes. Gosselet and Sebille (H7) tigated the influence of 8-c clodextrin-p-nitrophenol complexes on the retention a n i indirect detection of aliphatic alcohols in reversed-phase LC. The 8-cyclodextrin inclusion complexes provided detection enhancement. Takeuchi et al. (H8)reported indirect UV detection of cyclodextrins in microcolumn HPLC using theobromine and phenolphthalein as visualization agents. Detection mechanisms, perturbation of the partitioning process, and inclusion complexation were reported o timization discussed. Eppert and Liebscher (H9) experiments involving separation of position al€)y isomeric decanemonosulfonates using reversed-phase ion interaction chromatography with indirect UV detection. Dorland et (?. (H10) described an indirect W detection method for inorguc anions using tetrabutylammonium hydroxide and papaveraldine perchlorate as counterion and ion interaction reagent, ively. An “overload effect”, causing lowered peak areas an calculated displacement ratios, was observed, and a theoretical mechanism was proposed. Jurkiewicz (HI11 studied ion chromatographicseparation and indirect detection of various inorganic anions. He used simultaneous UV absorbance, fluorescenceand conductivity detection to evaluate 4-amino-1-naphthalenesulfonateand 6,7-dihydroxy-2naphthalenesulfonate as eluents. Danielson et al. (HI21 charactaid ion-exchangechroma aphy using vanadyl and vanadate salta as mobile phases, an they compared indirect UV detection with indirect electrochemical detection. In other reports of visualization enta for indirect detection, Maki and Danielson (H13, H I 3 evaluated naphthalenemono-, -di-, and 4risulfonates as mobile phases for ion chromatography of common inorganic and organic anions with indirect photometric detection. These reagents had the ades of not roducing a system peak and not requiring used Ru(phen):+ (phen E g z u s t m e n t . k e t n y k et al. (H15) = 1,lO-phenanthroline)and Ru(bpy)3z+(bpy = 2,2’-bipyridyl) for indirect photometric detection of small-chain peptide anions in basic mobile phase. The same workers (H16) used Fe(phen):+ for indirect detection of alkanesulfonatesand alkyl sulfates. Both studies (H15, H16) were done on a polystyrene-divinylbenzene copolymeric (Hamilton PRP-1) stationary phase. Jiang et al. (H17)studied henylalanine as an eluent for indirect UV detection of a l k J metals. Mehra H19)evaluated 4amino-2-hydroxybenzoic and Pelletier (H18, acid as an eluent for indirect UV detection of anions in single-column ion chromatography. Wangsa et al. (H20) examined indirect electrochemical detection of cations with cerium(II1) in the mobile phase.

7

262R


Finally, indirect detection formed an integral part of ionexchange studies performed on various stationar phases. Walker, Ha, and Akbari (H21423)evaluated cKromatographic analysis of organic anions and cations using low-capacity ion-exchange columns and indirect UV detection. These workers (H24)also compared silica-based strong ion exchangers and low-capacit polymer-based strong ion exchangers with indirect UV Jetection. Pietrzyk et al. (H25) studied simultaneous separation of inorganic cations and anions on a mixed-bed cation-anion exchange column with indirect UV detection. In an evaluation of columns packed with the polymeric anion-exch e stationary phase HEMA lo00 Q-L, Pacakova et al. ( H Yfound that the optimum conditions involved using an a ueous sulfosalilcylate mobile phase of pH > 4.5 and indirect%V photometric detection at 285 nm.

I. INFRARED DETECTORS The interface ‘oining LC and Fourier transform infrared Spectr~OPY( enerdy falls into one of two categories. Interfaces in which t i e effluent is scanned in a flow cell are commercially available, but the absorbance of the solvent limits sensitivity. The other approach is to vaporize the solvent, thus depoei the diesolved analytea on some moving media, ideally as sm spots which are then scanned. Most of the work focused on the solvent removal approach, particularly for microbore LC, where the amount of solvent is greatly reduced. A number of reviews appeared during the current period. Griffiths et al. (11, 12)described a unified approach for coupling gas chromato aphy (GC), high-performance liquid chromatogra hy (HFLC), and su ercritical fluid chromatography (SfC) to FTIR with onpy minor changes in the hardware. De Haseth and Robertson (13)reviewed the monodisperse aerosol generation (MAGIC) interface for HPLC-FTIR. The same workers also provided the first demonstration of identifiable IR spectra obtained from buffered (volatile and nonvolatile buffers) mobile phases using the MAGIC interface (14). Jinno and Fujimoto (15,16) reviewed microcolumn HPLC cou led with FTIR detection. Two general reviews of H P L C - d i R were also published (17, 18). Busch et al. (19)patented an infrared emission detector that was suitable for chromatographic a plications and for determination of total inorganic C, Cr, and available C12 in aqueous samples. The COz emission band (asymmetric stretch) at 4.3 pm, arising from sample introduction into an H2/air flame, was used with a dual-beam system for background subtraction. Lange, Griffiths, and Fraser (110) introduced a novel interface for microbore reversed-phase LCFTIR consisting of concentric fused-silica tubes for flow nebulization with warm He gas surrounding the inner tube containing the effluent and a rotatable stage for solute deposition. Complete removal of aqueous mobile phase was achieved for a flow rate of 50 pL/min. In a comparison of diffuse reflectance (DR) and diffuse transmittance (DT) infrared spectroscopy of HPLC-FTIR, Fraser, Norton, and Griffiths (111) found that DT-FTIR was useful following microbore LC, since the analytes penetrated well below the surface of the owdered substrate used for solvent removal, whereas DR-FbIR was superior when the analytes were deited in the top layer of the substrate, for example, following The buffer-memory technique, in which the total column effluent is deposited on a KBr crystal plate, was described b Jinno and Fujimoto (112)for combining microcolumn dPLC with FTIR and microprobe laser Raman spectroscopy. Several reports of FTIR interfaces were geared toward conventional scale LC. Huber and Frimmel(113) developed a cylindrical thin-film reactor for continuous flow injection analysis of inorganic and organic carbon and applied it as a low dead-volume or anic carbon detector for gel permeation chromatography. $he inorganic and organic carbon were separately converted to COz, which was quantitated by IR analysis. An HPLC interface, consisting of a thermos ra a moving stainless steel ribbon, and continuous DR-fTIg scanning of the eluates de osited on the ribbon was described by Jansen (114)and by R&rtson et al. (115). Shah et al. (116) used a flow cell based-FTIR detector for SFC and HPLC of steroids. The IR spectra of each steroid matched well for SFC

3

8%.


and HPLC, with the carbonyl bands shifted slightly to lower frequencies for HPLC.

J. LC/MS The combination of li uid chromatographic separation and mass spectroscopic(LCqhlS) detection is an important analytical techni ue. The technique is increasingly being used to identify ardytea in complex mixtures, because it offers high sensitivity and selectivity in the analysis of a wide range of compounds. Many LC/MS interfaces and ionization techniques were mentioned durin the review period including fast-atom-bombardment (FABf,thermospray, particle beap, electrospray, time-of-flight, ion trap, moving belt and inductively coupled and microwave-inducedplasmas. Revlews

Several comprehensive LC/MS review articles were written during the riod of this review. Probably the most extensive review of &was written by Burlingame, U n , Norwood, and Russell (51). New interfacin techniques for coupling capillary HPLC and fast-atom-bom%ardment(FAB) MS were reviewed by Ishii and Takeuchi (52). Atmospheric pressure interfaces for coupling chromatographic and electro horetic separation techniques with MS were reviewed by uang et al. (53). A eneral review of the ionization methods applicahle to the L C / b interface was written by B r u m (54). A review with 95 references of strategies for coupling LC and MS with ve was written by Niessen et al. (55). The a historical pers same authors 56) also wrote a review with 58 references outlining and discussing strategies for improving the compatibility and increasing the detectability of the tar et comound with pre- and postcolumn derivatization tecEni ues. h e mechanisms and techni ues of the thermospray LC'JMS interface were reviewed by pino (57).

8

p""

L

Fast Atom Bombardment (FAB)

An accurate mass measurement method based on computer-controlled internal mass calibration for dynamic FAB probe using known noninterfering masses of calibration standard to bracket the analyte eak of interest was re orted by Roboz et al. (J8).Sources of !and broadening in L&FAB systems were investi ated by Gagne, Carrier, and Bertrand (59)by precolumn aidition of glycerol to the mobile phase. Kokkonen et al. (510) listed some of the important arameters affecting the performance of continuous-flow &F) FAB. Including wettability and properties of the liquid film on the surface of the tar et. The same authors (511)developed a new target for CF %AB with a gold-plated drain channel, that gave higher optimum flow rates than acid-treated stainless steel targets.

of repeller voltage changes on spectra of some illustrative analytea, including polynuclear aromatic hydrocarbons, diuron, phenacetin, and caffeine. The authors (520)proposed mechanisms for repeller-induced LC/MS. Repeller effects are caused potential to the repeller electrode, positioned sample cone to increase sampling efficiency, which can induce fragmentation in thermospray MS. Particle Beam

Sanders (521)developed a particle beam interface for doing secondary ion mass s ctrometry. The interface allowed flow rates of up to 2.0 mGmin to be achieved. A particle beam interface was adapted to a double-focus' sector instrument of reverse geometry by Baczynskyi (522)%e instrument was capable of detecting high-picogram and low-nanogram levels of steroids. Ligon and Dorn (523) modified the particlebeam-type LC/MS interface to make it fully com atible with the vacuum requirements of a high-resolution dou le-focusing MS. Important features of the interface included a three-stage momentum separator, a nebulizer that is both ultrasonic and pneumatic, and an in-chamber desolvation heater. A simple, inexpensive direct liquid introduction system for interfacing LC to quadrapole and magnetic sector MS was reported by Gagne, Rouasis, and Bertrand (J24). The interface consists of a heated transfer fused-silica capill that introduces the mobile phase directly into the chemizionization source of the MS without a desolvation chamber. The authors report the system is stable, reproducible, and allows picogram range sensitivity to be achieved. A ffel and Perry (525) of Hewlett-Packard investigated the nonEnear behavior of particle-beam LC/MS systems at low concentrations and proposed a mathematical model that agreed with ex erimental data. The effects of 10 HPLC mobile-phaseaiditives and 24 analytical probes on linearit were shown. Some aspects of compound-dependent ea% broadenin in particle beam LC/MS were discussed by 3inke et al. (5267.

!

Electrobpray

Hiraoka and Kudaka (527) investigated various aspects of the electrospray interface, including the effect of needle voltage on total ion current, solvent dependence, the effect of surrounding gas, gas temperature, and the sensitivity of detection of mass-analyzed ions. Ikonomou et al. (528)used the electrospray LC MS interface to study various positive ions including N 4+, Na+, K+, Cs+,Ca+,and the protonated BHI ions of 30 organic nitrogen bases. Detection limits in the subfemtomole to attomole ran e were achieved. The sensitivity for the organic bases is pfI dependent and increases as the concentration of BH+ in solution increases.

d

Thermospray

llme of Fllght

Heeremans et al. (512) discussed optimization strategies for thermospray LC/MS. Vaporizer temperature, ammomum acetate Concentration, methanol content, and repeller were considered. Robins and Crow (513) discusse factors affecting high-mass sensitivity and ion-current stabilit of thermospray sources. Specifically, the authors (513) stuiied temperature control, vaporizer geometry, and the use of repeller electrodes. Genuit and Van Binsber en (514) were able to improve the ion-current stability of a t ermospray source by improving the control of the vaporizer temperature and solvent flow rate. Tinke et al. (515) discussed positively and negatively c y e d water cluster ions generated via LC thermospray MS. App 'cation of water cluster ions to tuning and d b r a t i o n was pro osed. A new vaporizer for thermospray LC/MS on doufle-focusing mass s ectrometes was reported by Ozaki, Mizuno, and Otsuka ( j . 6 ) . Kaiser et al. (517)performed thermospray LC/MS with a quadrupole ion trap mass spectrometer using corona discharge ionization to collect the spectra of a pe tide and a nucleotide. Several artick were written discussing the repeller effeds in discharge ionization. Niessen et al. (518) discussed the changes in reagent gas spectra for methanol/water and methanol/carbon dioxide mixtures roduced as a function of repeller voltage. The same authors 6 1 9 ) discussed the effects

Emary and co-workers (529) interfaced a HPLC system to a time-of-fli ht MS instrument. The interface served as a continuous-iow probe. The ions were desorbed from the liquid matrix by energetic ion bombardment. A high-s eed integrated transient recording system was also develo d a n d reported. The instrument is the prototype for the evelopspeed, high-mass :ange LC detector with high e HPLC time-of-fight MS system was further and spectra of peptide analytes were presented by the authors (530) in another article.

rtenm

E

t

Ion Spray

The first on-line coupling of microbore HPLC with an ion-trap mass spectrometer was reported by Henion and coworkers (531). The system used a pneumatically assisted electros ray (ion spray) LC MS interface to couple rev e r s e d - p L separations of bio ogically important compounds, including peptides and proteins, with the ion trap mass spectrometer.

f

Atmospherlc Pressure Ionlzatlon

A means of accomplishing atmospheric pressure ionization that avoids introducing the mobile phase directly into a ANALYTICAL CHEMISTRY, VOL. 64, NO. 12, JUNE 15, 1992

263R


high-vacuum ion source by utilizing ionization at atmos heric pressure was described by Henion and Lee (J32).T e approach forms ions from fine droplets, then extracts or focuses the aseous ions through a small orifice at the front of the mass anayzer. The authors claim neither the liquid effluent nor its vapor enters the high-vacuum region.

R

Membrane

Two researchers reported using micromembranes to modify the LC eluent prior to ionization. Simpson and co-workers (J33)used a membrane suppressor to remove nonvolatile alkaline salts after the separation of carbohydrates on an anion-exchange column and prior to the thermospray MS detection. Detection limits in the microgram range were reported. Conboy et al. (J34)used a micromembrane suppressor to remove 99.9% of the ion-pair agents required for the IC separation of quaternary ammonium drugs and tetraakylammonium compounds of industrial importance, prior to atmospheric pressure ionization and MS or MS/MS analysis. A limit of detection of 40 pg of injected tetrapropylammonium was reported. Column-Swltchlng

A column-switching technique was used by Asakawa et al. (J35)to overcome difficulties involved with a nonvolatile mobile phase. The peak of interest was heart-cut from the effluent of the analyticalcolumn and adsorbed onto a trapping column. The buffer constituents were washed out, and the compounds of interest were eluted from the trapping column by a mobile hase suitable for LC/MS. Kokkonen and coworkers (J367used a similar technique to enrich erythromycin-2’-ethylsuccinate on a short trapping column after analytical se aration, enabling optimal mobile phases and flow rates to e! used from both the HPLC separation and the CF-FABMS detection. Low Flow Delivery

A method for producing accurate, reproducible gradients at low microliter per minute flow-rates suitable for LC/MS applications using capillary columns was reported by Balo h and Stacey (J37). The technique employs a low-cost, weflcharacterized balance-column flow-splitter. Counter-Current Chromatography and High-speed Counter-Current Chromatography/MS

Oka et al. (J38) reported the first direct interfacing of high-speed counter-current chromatography with mass spectroscopy. Frit electron ionization, chemical ionization, and fast atom bombardment were demonstrated. Thermospray mass spectrometry was used by Lee et al. (J39)to demonstrate the resolving power of counter-current chromatography. Movlng Belt

Moini and Abramson (J40)described a movin -belt device that enables selective detection of 13C-and 15N-kbeled compounds. A thermospray vaporizer de osits the HPLC effluent onto a continuously moving endless Eelt. The belt carries the analytes into the chemical reaction interface, where a microwave-induced helium plasma converts the com lex organic molecules into small stable ions that are detectefby the MS system. Chromatograms showing only compounds with enriched 13C and 15N can be obtained by subtracting the abundance of the naturally occurring isotopes from the observed M + 1 signal. ICP/MS and MIP/MS

Heitkem er, Creed, and Caruso (J41)used a helium microwave-inzuced plasma mass spectrometer (MIP/MS) for the element-selective detection of halogenated organic comounds following reversed-phase separation. The detection ts were reported as 50 pg of Br for brominated compounds, 1 pg of I for iodinated compounds, and.10 ng of C1 for chlorinated compounds. The linear dynamic range for Br and I com ounds was 3-4 orders of magnitude. The linear range for t\e chlorinated species was limited by high background

Erm

284R


d

at m z = 35. Mason, Storms,and Jenkins (J42)demonstrated the easibility of using directly coupled size exclusion HPLC with inductively coupled plasma MS (ICP/MS) detection to separate and perform elemental analysis of metalloproteins. Data, on up to ei ht elements, were acquired simultaneously. Absolute and refative detection limits, reproducibility, operational dynamic range, and linearity of response were evaluated by analyzing metallothionein protein standards of known elemental composition. Kawabata et al. (543)used ion chromatography coupled with ICP MS to determine trace rareearth elements as impurities in ot er rareearth materials. Ion chromatography was used to separate the trace rare-earth elements from the main material, then the rare-earth elements were directly analyzed by ICP/MS. The detection limits for the 14 rare-earth elements ranged from 1 to 5 pg/mL in solution and ng/g in solid.

h

K. OPTICAL ACTIVITY DETECTORS Optical activity (OA) detection has grown in popularity, as is clear from the number of fundamental papers over the past 2 years. OA detection is comprised of three variations: polarimetry, circular dichroism (CD), and magnetooptical rotation (MOR). A olarimeter for HPLC is also commercially inlicating the need for this detector in many available (KI), laboratories. Lloyd and Goodall (K2)reviewed polarimetric detection, with emphasis on determination of enantiomeric purity and study of enantioselective reactions. Kawazumi et al. (K3)as well as Xi and Yeun (K4)developed a universal detedor for HPLC based on MdR, i.e. the Faraday effect, and have reported linearity results and detection limits. In a later work, Kawazumi et al. (K5)examined two suitable modulation modes for the MOR detector. Xu and Tran (K6)developed a novel and ultrasensitive HPLC detector, based on measurement of the thermal lens CD signal which corres onded to the difference in the thermal lens signal roducetf by sequential excitation of the effluent b left anfright circularly polarized laser light. Bertucci et a{ (K7)found that simultaneous measurement of the absorbance and CD signals allowed determination of the anisotropy factor and, hence, the optical purity of the eluates. Kurosu et al. (K8)applied gradient elution HPLC with CD detection to the separation and conformation analysis of proteins. Yamamoto et al. (K9)constructed a polarimetric detector from a photometric detector by placing two olarizers in the light ath on either side of the flow cell. M d r a t e sensitivity was gmonstrated for several sugars. Simultaneous polarimetric and absorbance HPLC detection was used by Goodall and co-workers (K10)to determine enantiomeric purity, for which an equation was given, and also by Mannschreck and Kiessl (KII)to study enantiomerization, for which deconvolved chromatograms were obtained, showing the relative concentrations of the enantiomers. Bobbitt and co-workers (K12,K13) found that combination of HPLC with laser-based polarimetric detection provided unique advantages for analysis of penicillin analogues (K12)and entamicin analogues in milk (K13). He aud and Rinaudo &14) used polarimetric, refractive i n g x , and light scattering detection for characterization of dextrins and starches using gel permeation and reversed-phase LC.

L. REFRACTIVE INDEX DETECTORS The RI detector is the most popular “universal” detector for LC, but it is limited by fluctuations in eluent RI due to changes in temperature, pressure, composition, and diasolved gases. Much of the recent work has been directed toward minimizing these limitations in the RI detector erformance. Bruno et al. (L1)reported an on-column laser%ased RI detector for capillary electrophoresis that exploited the interference pattern from side-illuminated capillary tubes. The reported RMS noise level of 3 X lo* RI units was only 1order of magnitude eater than the calculated shot noise limit. Three reports (f2-L4)were published in which peak identity and homogeneity were ascertained by ratioing the response factors from simultaneous UV and RI detection. Weigang et al. (L2)developed a cation-exchange LC method for the determination of carbohydrate substrates and excreted metabolites in mammalian cell cultures. Masson et al. (L3)de-

COLUMN LIQUID CHROMATOQRAPHY

veloped a cation-exchange LC method to analyze metabolites in the effluents from perfused rat livers. Vaccher et al. (L4) developed an HPLC method for lactulose and related sugars (lactose, fructose, galactose, epilactose) using an (aminopropy1)silyl stationary phase. The refractive index gradient (RIG) detector has the advantage that drift and low frequency fluctuations in eluent RI are smoothed out, while maintaining good sensitivity to the analytss. In this detector, a laser beam passing axially through the flow cell is deflected in proportion to the radial RI gradient that is caused by the dispersed analyte concentration profile, and this deflection is quantitative1 sensed. Synovec, Renn, and Hancock (L5-L7) continued t i e development of the refractive index gradient (RIG) detector for microcolumn HPLC. A simple model for RIG detection sensitivity, based upon Poiseuille flow within the Z-confi ration flow cell, was ex erimentally supported for Reynogs numbers below 10 ( L d . The RIG signal was directly proportional to the linear flow velocity and inversely proportional to the axial length variance of the analyte concentration profile. In other work (I&), the RIG detector was successfully applied in both mobile-phase gradient and thermal gradient microbore LC. Both gradient modes were evaluated using mixtures of n-alkanesand 1,2-diacylphosphatidylcholines.The laser probe-beam position for optimum sensitivity was found using fiber optic techniques. Further details and refiements afforded by fiber optic technology to the RIG detector, allowing flow cell volumes of 1-3 pL, were also reported (L7).

M. MISCELLANEOUS DETECTORS Atomic Absorbance Spectrometry (AAS). The inter-

faces for the determination of ionic alkyllead, alkyltin, arsonium, and selenonium compounds by HPLC-AAS were reviewed by Marshall, Blais, and Adams (MI). Weber and Bemdt (M2)re rted a hydraulic hi h-pressure nebulizer for couplin H P L p t o flame-atomic atsorption spectrometry (AAS). bignal enhancementswere observed and effecta of flow rate and nebulization nozzle diameter were investigated. An ultrasonic nebulizer interface system for coupling LC and electrothermalAAS was develo by Stupar and Frech (M3). Blais et al. (M4) developed an characterized a thermochemical h dride eneration interface for determining As species by H J L C - d S . B1ais and Marshall (M5) used a continuous postcolumn ethylate enerator to volatilize alkyllead compounds separated by k P L C for AA determination with detection limits approaching 0.1 ng. Atomic Emission Spectrometry ( U S ) . Atomic emission detectors are used primarily as element-specific LC detectors. investigated the utility of using Lewis, Nam, and Urasa (M6) a direct-current plasma to determine the transformations that element s ecies undergo as solution conditions change. compared thermospray Ro chowdkuy and Koropchak (M7) a n i pneumatic sample introduction for inductively coupled plasma (ICP). Detection limits for chromium species separated by ion chromatography were improved by factors of 24 and 36, respectively, for 50- and 25-pm apertures for thermospray compared to neumatic sam le introduction. Elgersma, Balke, and hfaessen (M8)gveloped a low consumption thermospray nebulizer with detection limits for 10 test elements at the ng/mL level for micro-HPLC with ICPAES detection. Pomeroy, Kolczynski, and Denton (M9) developed a direct current plasma echelle/charge injection device spectroscopic system for AES. The system uses an information-based ex ert system to select the optimal emission used laser-excited atomic wavelength. W&on et al. (M10) fluorescence spectromet (LEAFS) in a flame as a detector for organomanganese an organotin compounds. Detection limits ranged from 8 to 22 pg of manganese. Electron Spin Resonance. Zolotov et al. ( M I I )described ibilities of the application of electron spin resonance as a method of detedion in HPLC. No special interface was required for connecting a commercially available chromato aph and an ESR spectrometer. The ESR detection was gmonstrated by determining a number of metals in the form of their complexes with spin-labeled nitrosyl-containing M was achieved for reagents. A detection limit of 1 X mercury(I1). Flame Ionization. Berezikin (M12) presented a review with 90 references of the up-to-date state of non-hydrogen

B"d

7

t%r

flame-formingagents and prospects for applying them in flame ionization detectors for gas and liquid chromatography. A novel transport detector for LC was developed by Malcomle-Lawes and Moss (MI3). The detector employs a number of novel features, which allow close control of solvent removal and permit the detector to be used for relatively volatile sample materials. Ion Mobility. Ion mobility spectrometry detection for LC with corona-spray ionization was discussed by Hill and coworkers (MI4). Light Scattering (Evaporative). This type of detector has often been referred to by the follo names: evaporative light scattering detector (ELSD), masyetector ,evaporative analyzer, and nephelometer. The intensity of li ht scattered by solute particles formed after nebulization anf evaporation of the eluent from a chromatographic column is measured. It should not be confused with low-an le laser light scattering detectors. Dreux and Lafosse (MI51 iescribed the princi les of the ELSD and ita use in HPLC and supercritical fkuid chromatography. The same authors (M16)described the development of new methodologies for analyzing complex mixtures. The sensitivity of the ELSD depended on the eluent composition and the analyte concentration. Under reversed-phase gradient conditions, calibration is necessary for each analyte. Mengerink et al. (M17) determined the detection limits for alcohol and carboxylic acid homologues using ELSD. The authors found that the advantages of helium over carbon dioxide as a nebulization gas for both volatile and nonvolatile or thermolabile analytes were a more than 30 deg lower operating temperature and a 5-fold better signal-to-noise ratio. They also found that ELSD, compared with refractive index and UV absorbance detection at 190 nm, was superior in signal-to-noise ratio as well as baseline drift. Elfakir et al. (MI@also found that ELSD was superior to refractive index detection for similar reasons. Stockwell and King (MI9) illustrated the advantages of ELSD for LC relative to refractive index and W detectors. Lutzki and Bra hler (M20) developed a new ELSD and reported a limit ofyetection of 50 ng for neutral lipid and 200 ng for most phospholipids with excellent reproducibility. Drogue et al. (M21)reported a first attempt to use an ELSD for on-line detection in high-speed counter-current chromatography. Molecular Size (Light Scattering) Detector. Claes et al. (M22)reported an on-line determination of macromolecular sizes in the 2-40-nm range corresponding to a molecular weight range of 12 000-50 000OOO by the Oros 801 molecular size detector, based on light scattering. Suck (M23) described a molecular weight sensitive detector which works by dscattering of laser radiation for the determination of mol%% weight by ion-exclusion chromatography. Nuclear Magnetic Resonance Spectroscopy. The instrumentation, methodology, and limits of direct couplin between HPLC and 'HNMR spectroscopy were describe% and the advantages of the method were discussed by Grenier-Loustalot et al. (M24). An application of this technique to obtain structural and mechanistic data was given. Ilg et were able to reveal band profiles, on preparative al. (M25) columns in LC, with the help of NMR imagin on a real time basis. For the first time, the authors confiiecfthe wall effect, which has been theoretical1 predicted, by proton images. Frankel et al. (M26) used 2C NMR spectroscopy to study structures and for quantitative determination of the positional and stereoisomers of methyl linoleate hydroperoxides. Particle Detector. Chromatographic detection of particles 0.05-10.0mm in diameter by using capillary tubes was reported by Shiragami (M27). Retention times of particles depended on the diameter. The application of this technique as a detectin method for contaminanta in a bioreactor was demonstrate!. Phosphorescence. The use of room-tem erature phosphorescence detection including direct phospiorescence detection, sensitized techniques, and quenchin techniques in LC was reviewed by Prognon et al. (M28). tampi lia et al. (M29) optimized a two-nebulizer system for soli8-surface room-temperature hosphorescence (SSRTP) as a selective permanent record &tector for HPLC. The authors obtained calibration c w e s with satisfactory linear dynamic ranges and limits of detection in the nanogram and subnanogram level claiming the feasibility of the SSRTP detector for HPLC. ANALYTICAL CHEMISTRY, VOL. 64, NO. 12, JUNE 15, 1992

265R


Further, the selectivity of the SSRTP detector was demonstrated by individually identifying overlapped compounds. Photoionization. Dominant noises related to leakage currents were discussed by Voigtman and Snyder (M30) in sequential, two- hoton photoionization in polar solvent systems under HPEC conditions. Five benzodiaze ines were separated and deteded using a system that includda baseline restorer preamplifier. No optimum preamplifier was found, articularlywhere solvent programming applications are used. chmermund and Locke 0431) reported an automated liquid to va r phase, six-valve interface that enables peak tra ping on a E n a x trap after dilution of the effluent with a sokent. The solvent was evaporated, and then the trapped solute was flash evaporated in the vapor phase photoionization system. Techniques for both normal- and reversed-phase separations were reported. Detection limits for phenobarbital were 2 ng. constructed a postcolumn photoconMiles and Zhou (M32) ductivity detector to determine several classes of pesticides and herbicides. Effects of solvent composition and photolysis coil material on the detector response were reported. Multivariate optimization using a factorial experimental design for photolysiswas applied by Bachman and Stewart (M33) amperometric detection. Experimental results were used to determine optimum conditions, visualize the interactions between pH and irradiation time, and propose a low-cost used on-line photochemical reactor. Turk and Kingston (MN) chelation chromatography as a sample clean-up technique to remove interferences from alkali and alkali earth metals in laser-enhanced ionization spectrometry. This procedure allowed the sensitive determination of trace metals in biological and environmental samples. Radioactivity. Two reviews appeared, concerning radioand radioactivity flow detection chemical quantitation (M35) (M36) for HPLC. Using continuous postcolumn extraction of aqueous column eluates with a water-immiscible liquid scintillator, Veltkamp et al. (M37) demonstrated radioactivity detection of tritium and carbon-14 labeled compounds in reversed-phase LC, with counting efficiencies of 30% and 80%, respectively. Bradbury et al. (M38) achieved rapid analysis of non-y radionuclides using the ANABET system (analysisof a,8, and electron capture radionuclide techno1 ), consisting of ion-exchange chromatography followed by on%, scintillation detection. Reversed-phase HPLC with liquid scintillation radioactivity detection was applied to the determination of selenium-75 labeled selenite and metabolites (M39) and to the determination of carbon-14 labeled soilTheimer bound atrazine and four of its metabolites (M40). used anion exchange followed by radioand Krivan (M41) chemical neutron activation analysis to determine uranium, thorium, and 18 other elements in high-purity molybdenum. used cation exchange followed by irradiSmith et al. (M42) ation neutron activation analysis to determine rare-earth elements in geologic samples. Raman (Surface-Enhanced). Recent application of surface-enhanced Raman spectroscopy (SERS) to real-time detection in HPLC and flow injection analysis (FIA)has been accomplished. Advantages of such a technique, as reported include sensitivity, specificity (moby Cotton et al. (M43), lecular fiierprint),versatility, and detection limita that should be comparable to UV spectroscopy. In the above work using Ag sols as the active substrate, temperature, H, flow rate, and the HPLC/spectxometer interface were stuied. At higher temperatures, increased colloid aggregation produces larger the and more rapid SERS signals. In another work (M44), above authors studied similar parameters in the detection of purine bases separated by reversed-phase HPLC with detection limits ranging from l to 10 nmol. Both three-dimensional (SERS intensity, Raman shift, and time) and two-dimensional (SERS intensity and time) chromatograms were presented. In an earlier SERS-FIA study, with im li cations for HPLC, the above authors (M45)reportel real-time measurement of RNA bases by FIA. The effects of H, temperature, flow rate, and tubin material on the SEkS spectra were reported using Ag so% as a substrate Pothier and Force 0446)developed a 30-pL flow cell fo; SERS-FIA that incorporated a silver electrode as the substrate. An optical multichannel analyzer produced highquali spectra with integration times less than 5 s. Detection limitakhveen 175and 233 pmol for DNA b m were reported, and samples were rapidly desorbed off the surface in less than

H

a

266R


10 s. The authors suggested promise for this technique in HPLC detection. Final1 , Soper et al. (M47)reported an off-line surface-enhancei resonance Raman spectroscopy ( S E W ) detection system. Analytm eluted from a LC system onto a thin-layer chromatography (TLC) plate. Next, an activated Ag sol was added to the plate. Finally, the SERRS was monitored by a Raman spectrometer equipped with i umination and collection fiber optics for remote sensing. The solid matrix system prevents further ag e ation of Agdye complex thereby giving stable, extendefSkRRS intensities with a detection limit of 750 fmol for pararosaniline acetate. Viscosity Detector. The differential viscometer is sensitive and provides accurate measurements of minor changes of Viscotek Corp. demonin viscosity. Dutta et al. (M48) strated that the Viscotek differential viscometer can be used as an on-line detector for HPLC, to monitor the viscosity of the column effluent. The advantages of using the differential viscometer instead of a conventional glass ca illary viscometer is the increased sensitivity, precision, speedJ and operational ease that permits measurement of solution viscosity of low sample concentrations u to 1.2 pg of pure proteins. Yau (M49) patented a methotf which measures the inherent viscosity of individual solute components in a multicomponent sample solution.

SF.

LITERATURE CITED A. COLUMNS

( A l ) Schomburg, G. Cbromatograpbla 1990, 30, 500-8. (A2) Hirata. Y. J. M l m o l u m n Sep. 1990, 2 , 214-21. (A3) Chizhkov, V. P.; Varivonchik, E. A.; Goryachko, Y. V.; Zabokritskil. M. P.; Landau, V. V. Z b . Anal. Kblm. 1990, 45, 1798-806. (A4) Andreev, V. P.; Khidekel, M. I . Zb. Flz. Kblm. 1991, 65, 2814-9. (A5) Ying, P. T.; Dorsey. J. 0. Talanfa 1091, 38, 237-43. (A6) Snyder, L. R.; Cox, 0. B. J. Chromafogr. 1989, 483. 85-94. (A7) Novak, I.; Buszewski, 6.; Garaj, J.; Berek, D. Cbem. Pap. 1990, 4 4 , 31-43. (AB) Maliett, D.N.; Law, B. J. pherm. Bbmed. Anal. 1991, 9 , 53-7. (A9) Alhedai, A.; Martire, D.E.; Scott, R. P. W. Analyst 1989, 714, 869-75. (A10) Magnico, P.; Martin, M. J. Cbromatogr. 1890, 517, 31-49. ( A l l ) Wang, T.; Hartwick, R. A.; Miller, N. T.; Shelly. D. C. J. Cbromatogr. 1990, 523, 22-34. (A12) S h a h , Y. PCT Int. Appi. WO 9114490 A l , 3 Oct 1991, 38 pp. (A13) Zogg, G. C.; Nyiredy, S.; Sticher, 0. J. Llq. Cbromtogr. 1989, 12, 2031-48. (A14) Liao, J. L.; Zhang, R.; Hjerten, S. J. Cbromatogu. 1991, 586, 21-6. (A15) Van Berkel-Geldof, 0.; Kraak, J. C.; Poppe, H. J. C b r m t o g r . 1990. 499, 345-59. (A16) Eguchi, S.; Kiwsterboer, J. G.; Zegers, C. P. G.;Schoenmakers, P. J.; Tock, P. P. H.; Kraak, J. C.; Poppe, H. J. Cbromfogr. 1990, 576. 30 1- 12. (A17) Eguchi, S.; Kiwsterboer, J. 0.;Dirk, J. Eur. Pat. Appi. EP 414324 A l , 27 Feb 1991, 10 pp. (A18) Ito, M.; Satake, H.; Takata, Y. Ger. Offen. DE 3939854 A l , 13 Jun 1990, 8 pp. (A19) America, W. 0. Eur. Pat. Appl. EP 328146 A2, 16 Aug 1989, 7 pp. (A20) COX, 0. B. LC-QC 1990, 8, 690, 692-4. (A21) Ge, H.; Wailace. G. G. J. Llq. Chrometogr. 1991, 74. 1815-29. (A22) Nawrocki, J. Cbromafograpbla 1991, 31, 193-205. (A23) Tanaka, N.; Kimata. K.; Araki, T.; Tsuchiya, H.; Hashizume, K. J. Cbromefcgr. 1991, 544, 317-44. (A24) Takeuchi, T.; Hu, W.; Haraguchi, H.; Ishii, D. J. C b r m f o g r . 1990, 577, 257-62. (A25) Jinno, K. J. Cbromatogr. Scl. 1989, 27, 729-34. (A26) Jeng. C. Y.; Langer, S. H. J. Cbromatogr. Scl. 1989. 27, 549-52. (A27) Law, 6.; Chan, P. F. J. Chromafogr. 1989, 467, 267-71. (A28) Pfannkoch, E. A.; Swker. B. S.; Kopaciewicz, W. J. Cbromatogr. 1990, 503, 385-401. (A29) Verzele, M.; Dewaele, C.; De Weerdt. M.; Abbott, S. J . H@I Resolut. Cbromatogr. 1988, 72, 164-8. (A30) Dolan, J. W. LC-GC 1989, 7 , 556. 558. 560. (A31) D o h . J. W. LC-GC 1890, 8, 358. 380.

B. INSTRUMENTATION (61) Berry, V. Cr#. Rev. Anal. Chem. 1989, 27, 115-91. (82) Aieksandrov, M. L.; Andreev, V. P. Fresenlus’ 2.Anal. Chem. 1989. 335, 2-8. (83) Goto. M.; Takeuchi, T.; Ishii, D. A&. Cbromafogr. ( N . Y . ) 1989, 30, 187-99. (84) Ruzicka, J.; Chrlstian, 0.D. Analysf 1000, 715, 475-86. (85) Manz, A.; Miyahara, Y.; Miura, J.; Watanabe, Y.; Mlyagi, H.; Sato, K. Sens. Actuatovs 1990. B 7 , 249-55. (66) Monnig, C. A.; Dohmeler, D. M.; Jorgenson, J. W. Anal. Chem. 1991, 63,807-10. (87) Hoizhauer-Rieger, K.; Zhou, W.; Schuegeri, K. J . Cbromatogr. 1990, 499, 609-15. (88) Guillemin, C. L. Trends Anal. Chem. (fers. Ed.) 1989, 8, 273-6. (69) Favre, E.; Pugeaud, P.; Raboud, J. P.; Peringer, P. J. Autom. Chem. 1989, 11, 280-3.

COLUMN LIQUID CHROMATOORAPHY (810) Peesen, J.; Hoogmartens, J. LC-OC 1990, 8 , 696, 698. (811) Schnelder. W.; WM, K. Ew. Pat. Appl. EP 438188 A l , 24 Jan 1991. 10 PP. (812) Tyrefors, N. Anal. Chem. 1991, 63,1901-2. (813) Senders, L. C.; Craft, N. E. Anal. Chem. 1990, 62. 1545-7. (814) Shlrato, K.; Chatfbld, C. G.; Nevlus, T. A. Am. Lab. 1991, 23, 36N38T. (815) Stubba, W. Labcrprexls 1989, 73,758-60, 762. (816) Eberhard, A.; Stranlck. S. J.; MacNell, J. LC-OC 1991, 9 , 132, 134. (817) Dasgupta, P. K.; Strong, D. L.; Stllllan, J. R.; Frledman, K. A. Eur. Pat. Appl, EP 442224 A2, 21 Aug 1991, 20 pp. (818) Miller, L. A.; Shafer, R. U.S. 4905161 A, 27 Feb 1990, 9 pp. (819) Sheehan, T.; Schachterle, S. LC-OC, 1990, 8 , 726, 728-31. (820) LedtJe, M.; Long, D. Jr. U.S. 4862907 A, 5 Sep 1989, 7 pp. (821) Rlsler, W.; Nagel, U. Qer. Offen. DE 3837325 A l , 10 May 1990, 8 pp. (822) Bruin, G. J. M.; Tock, P. P. H.; Kraak. J. C.; Poppe, H. J. chrometogr. 1990, 577, 557-72. (823) Pfeffer. W. D.; Yeung. E. S. Anal. Chem. 1990, 62. 2178-82. (824) Obst, D. Ger. (East) DD 278838 A l , 16 May 1990, 4 pp. (825) James, P. A. Ew. Pat. Appl. EP 341784 A2, 15 Nov 1989, 10 pp, (826) LeBlanc, J. C. Rev. Scl. Instum. 1991, 62, 1642-6. (827) Trlsclanl, A.; Andreollnl, F. J. High Resolut. Chromatogr. 1990, 73, 270-4. (828) Trlsclanl, A.; Andreollnl, F. Eur. Pat. Appl. EP 377202 A2. 11 Jul 1990, 7 PP. (829) Hue, X.; Slouffl, A. M. Spectra 2000 1990. Suppl. 15, 21-3. (830) Banks, J. F., Jr.; Novotny, M. V. J. Microcohnnn Sep. 1990. 2 . 84-7. (831) Munk, M. N. US. 4942018 A, 17 Jul 1990, 24 pp. (832) Beny, V.; Van Rossum, P.; Pretorlus, V. J. Liq. Chromatogr. 1990. 73,391-407. (833) Bauer, H. Chrometcgraphk 1989, 28. 289-92. (834) Claemsens, H. A.; Murclnova, A.; Cramers, C. A.; Mussche, P.; Van Tlburg, C. C. E. J. Mluocoumn Sep 1990. 2 , 132-7. (835) Mars, C.; Smt, H. C. Anal. Chlm. Acta 1990, 228. 193-208. (836) Engelsma, M.; Louwerse, D. J.; Boelens, H. F. M.; Kok, W. T.; Smt, H. C. Anal. Chim. Acta 1990, 228, 209-27. (837) Evans, C. E.; McGuffln, V. L. Anal. Chem. 1991, 63, 1393-402. (838) Nlckerson. M. A.; Poole, J. S.; Frank, L. G. R. Eur. Pat. Appl. EP 384969 A2. 5 Sep 1990, 8 pp. (839) Debts, A. J. J.; Huw, K. P.; Brlnkman, U. A. T.; Kok, W. T. Chromatograph& 1990, 29, 2i7-22. (840) Mlller, L.; Bwh, H.; DenicO, E. M. J . ChfOt7IatOgr. 1989, 484, 259-65. (841) Pavllk, M.; Jehnlcka, J.; Kostka, V. Collect. Czech. Chem. Commun. 1989. 54. 940-4. (842) Sgourakes, G. E.; Kozlol, S. Eur. Pat. Appl. EP 421463 A2. 10 Aprll 1991, 9 pp. (843) Halvax, J. J.; Wlese, G.; Van Bennekom, W. P.; But, A. Anal. Chim. Acta 1990, 239, 171-9. (844) Del Mar, P.; Hemberger, 8. J. U.S. 5037553 A, 6 Aug 1991, 7 pp. (845) Haglnaka, J.; Wakal, J. J. Chromatogr. 1990, 502, 317-24. (846) Nohl, A. Eur. Pat. Appl. EP 385026 A2. 5 Sep 1990, 7 pp. (847) Perkins, R.; Nohl, A.; Pohlt, A. LC-GC 1990, 8 , 238, 240-1. 1848) Vwel. W. LabwRaxls 1990. 74. 936. 938. 940. 942-4. iB49j Tui&a, L. G. M. T.; Klenhuls, P. ‘G. M.; Traag, W. A.; Aerts, M. M. L.; Beek, W. M. L. J. J. Hlgh Resolut. Chromatogr. 1989, 72, 709-13. (850) Aerts, M. M. L.; Beek, W. M. J.; Brlnkman, U. A. T. J. Chromatogr. 1990, 500, 453-68. (851) Agasoester, T.; Rasmussen, K. E. J. Chromatogr. 1991, 570, 99-107. _. (852) Nllve, G.; Audunsson, G.; Joensson, J. A. J. Chromatogr. 1989, 477, 151-60. (853) llmmoney, P.; Newton, S.; Beak, P. A&. Lab. Autom. Rob. 1989, 5 , 249-65. (854) Slmonson, L. A.; Llghtbcdy, 8. Lab. Rob. Autom. 1990, 2 , 221-8. (855) Picot, V. S.; Doyle, E.; Pearce, J. C. J. Chromatcgr. 1990, 527, 454-60. (856) Simon, P. K.; Dasgupta, P. K.; Vecera, 2. Anal. Chem. 1991. 63, 1237-42. (857) Brereton. R. G. Anal. Roc. (London) 1991, 28, 145-7. (858) Haddad, P. R.; Soslmenko, A. D. J. Chromatogr. Scl. 1989, 27, 456-6 1. (859) Kenny, A. C. Bbprocess Techno/. 1990, 9 , 603-16. (860) Van Leeuwen, J. A.; Vandeglnste, 8. G. M.; Postma. G. J.; Kateman, G. Chemom. Intell. Lab. Sysf. 1989, 6 , 239-52. (861) Warren, F. V., Jr.; Phoebe, C. H., Jr.; Webb, M.; Weston, A.; BMllngM Y W , 8. A. Am. Lab. 1990, 22, 17-20, 22, 24-8. (862) Rooney, T.; Chell, C.; Bell, R. Am. Lab. 1990, 22, 28X, 282, 28AA. (863) DJordJevlc, N. M.; Ernl, F.; Schrelber, 8.; Lankmayr, E. P.; WegscheidW, W.; Jaufmann, L. J. Chrometogr. 1991. 550, 27-37. (864) Jlnno, K.; Yamagaml, M.; Kuwajlma. M. J. Chmmatogr. 1989, 485, 461-75. (865) Zhang, Y.; Zou, H.; Lu, P. J. Chromatogr. 1990, 575, 13-26. (866) Tsujl, K.; Jenkins, K. M. J. Chromatogr. 1989, 485, 297-309. (867) Matsuda, R.; Hayashl, Y. Chromatograph& 1990, 30, 371-6. (868) Hayashl, Y.; Matsuda, R. Chfomatognphia 1990, 30, 171-5. (869) Felder, R. A. Drugs. Pharm. Scl. 1991, 47, 185-210. (870) Russell, J.; Boyd, T. Adv. Lab. Autom. Rob. 1991, 7 , 451-64. (871) Lloyd, T. L.; Lang, J. R. A&. Lab. Autom. Rob. 1990, 7 , 73-87. (872) pleta, L. Adv. Lab. Autom. Rob. 1991, 7 , 303-13. (873) Khgeton, H. M.; Ruegg, F.; DeVoe. J.; Clements, C. Adv. Lab. A m m . Rob. 1989, 5 , 27-35. (874) Franc, J. E.; Duncan, G. F.; Farmen, R. H.; PMman, K. A. J. Chromatog.1991, 570, 129-38. (875) Brunner, L. A.; Juders. R. C. J. Chmmatogr. Sci. 1991, 29, 287-91. (876) Chang, M.; Kosobud. L.: Schoenhard. 0. A&. Lab. Autom. Rob. 1989, 5, 433-40.

(B77) Hartshorn, L. A., Zepchl. M. T.; Bueno, C. S. Adv. Lab. Autom. Rob. 1989, 5 , 235-47. (878) Kanczewski, E. 0.; Doerlg, R.; Skrllec, M.; Daly, R. E. Lab. Rob. Autom. 1990, 2 . 229-33. (879) Thoma, R. S.; Crlmmlns, D. L. J. Chromatogr. 1991, 537, 153-65. C. DETECTORS

(Cl)Yeung, E. S. J. Chin. Chem. Soc. (Talpel) 1991, 38, 307-12. (C2) Berthod, A. Specffochim. Acta Rev. 1990, 73, 11-25. (C3) Belen’kll, 8. G. Zh. Anal. Khim. 1990, 45, 643-64; Chem. Abstr. 1990, 713, 3 4 1 5 7 ~ . (C4) Dasgupta. P. K. J. Chromatogr. Sci. 1989, 27, 422-48. (C5) Rocklln, R. D. J. Chromatogr. 1991, 546, 175-87. (C8) Synovec, R. E. AIP Conl. Roc. 1989, 197. 716-21. D. ABSORBANCE DETECTORS

(Dl) Huber, L.; Fledler, H. P. L h g s Pharm. Scl. 1991, 47, 123-46. (D2) Jones, K. P. Trends Anal. Chem. 1990. 9 , 195-9. (D3) Oonnord, M. F.; Sio~ffl,A. M. J. Pianar Chromatogr.-W. n C 1990, 3, 206-9. (134) XI, X.; Yeung, E. S. Anal. Chem. 1990, 62, 1580-5. (D5) Renn, C. N.; Synovec, R. E. Anal. Chem. 1990, 62, 558-64. (D6) Synovec. R. E.; Renn, C. N.; Moore. L. K. Roc. SPIE-Int. Soc. Opt. Eng. 1990, 7772, 49-59. (D7) Renn, C. N.; Synovec, R. E. Anal. Chem. 1991, 63,568-74. (D8) Sulya, A. W.; Moore. L. K.; Synovec, R. E. Roc. SPE-Int. Soc. Opt. EnQ. 1991, 7434, 147-58. (D9) Evans, C. E.; McGuffln, V. L. J. Chromatogr. 1990, 503, 127-54. (D10) Bruin, G. J. M.; Stegeman, G.; Van Asten, A. C.; Xu, X.; Kraak, J. C.; POPW, H. J . ChrOmatOgr. 1991. 559, 163-81. ( D l l ) Chervet, J. P.; Ursem, M.; Salzmann, J. P.; Vannoort, R. W. J. H@h Resolut. Chromatogr. 1989, 72, 278-81. (D12) Tsuda, T.; Kobayashi, Y. J. Chromatogr. 1990, 575, 357-61. (D13) Kamahorl, M.; Watanabe, Y.; Mlyagl, H.; Ohkl. H.;Miyake, R. J. Chromatogr. 1991,549, 101-11. 0 1 4 ) De Andrade, J. C.; Collins, K. E.; Ferrelra, M. Analyst 1991, 176, 905-7. (D15) Verrele, M.; Steenbeke, 0.; Vlndevogel, J. J. Chromatog*. 1989, 477, 87-93. (D16) Esqulvel, H.; Benjamin, J. US. US 4886965 A, 12 Dec 1989, 4 pp. (D17) Binder, S. R.; Adams, A. K.; Regalla, M.; Esslen, H.; Rosenblum. R. J. ChrOmatOgr. 1991, 550, 449-59. (Dl8) Bogusz, M.; Wu, M. J. Anal. Toxlcol. 1991, 15, 188-97. (Dl9) Hayashl, Y.; Matsuda, R.; Nakamura, A. J. Chromatcgr. Sci. 1990, 28, 628-32. (D20) Hayashi. Y.; Matsuda, R. Anal. Scl. 1989, 5 , 459-64. 0321) Jandera. P.; Prokes. 8. J. chrometogr. 1991, 550, 495-506. (D22) Chan, H. K.; Carr, G. P. J. Pham?. Blomed. Anal. 1990, 8 , 271-7. (D23) Blaffert, T. Ger. Offen. DE 3827066 A l , 15 Feb 1990, 7 pp. (D24) Wolf, C.; SchmM. R. W. J. Llq. Chromatogr. 1990, 73, 2207-16. (D25) Domlnguez. E.; Markc-Varga, 0.; Carlsson, M.; Gorton, L. J. Phann. BiomSd. Anal. 1990, 8 , 825-30. 0 2 6 ) Leon-Oonzalez, M. E.; Townshend, A. J. Chromatogr. 1991. 539, 47-54. (D27) Babe, Y.; Tsuhako, M.; Yoza, N. J. Chromatogr. 1990, 507, 103-11. (D28) Schaufelberger, D. E. J. Liq. Chromatogr. 1989, 72, 2263-80. (D29) Oka, H.; Ito, Y. J. Chromatogr. 1989, 475, 229-35. E. CHEMILUMINESCENCE DETECTORS

(El) Nleman, T. A. In Chemlluminescence and Photochemical Reactbn Detectlon In Chromatography; Blrks, J. w., Ed.; VCH New York, 1989; pp 99-123. (E2) Nleman, T. A. Ract. Spectrosc. 1991. 72, 523-65. (E3) Fujlwara, T.; Kumamaru, T. Spectrochim. Acta Rev. 1990. 73, 399-406. (E4) Townshend, A. Analyst 1990, 775, 495-500. (E5) ImaL K. ChrOmatOgr. SCi. 1990, 48, 359-79. (E6) Givens, R. S.; Jencen, D. A.; Rlley, C. M.; Stobaugh, J. F.; Chdtshl, H.; Hanaoka, N. J. Pharm. Bbmed. Anal. 1990, 8 , 477-91. (E7) Blrks, J. W., Ed. Chemllumlnescence andPh4tochemIcalReactbn Detection In Chromatography; VCH: New York, 1989. (E81 Schreurs, M.; Oool@r. C.; Velthorst, N. H. Anal. Chem. 1990, 82, 2051-3. (€9) Chang. H. C. K.; Taylor, L. T. Anal. Chem. 1991, 63, 486-90. (E10) Jalklan, R. D.; Ratzlaff, K. L.; Denton, M. 8. Roc. SPE-Int. Soc. Opt. Eng. 1989, 7055, 123-34. ( E l l ) Baeyens, W.; Bruggeman, J.; Dewaele, C.; Un, 8.; Imal, K. J. Bklumin. Chemllumin. 1990, 5 , 13-23. (€12) Hanaoka, N. J. Chromatogr. 1990, 503, 155-65. (E13) Jones, P.; Wllllams, T.; Ebdon, L. Anal. Chlm. Acta 1990, 237, 291-8. (E141 Poulsen, J. R.; Blrks. J. W. Anal. Chem. 1990, 62, 1242-51. (E19 Kwakman, P. J. M.; Kammlnga, D. A.; Brlnkman, U. A. Th.; De Jong, G. J. J. Chromatogr. 1991, 553, 345-56. (E16) Alchlnger, 1.; Guebltz, G.; Blrks. J. W. J. Chmmatogr. 1990, 523, 163-72. (E17) Kawasaki, H.;Maeda. N.; Yukl. H. J. C h m t o g r . 1990, 576.450-5. (El8) Maeda. M.; Shlmada, S.; Tsujl. A. J. Chromatog. 1990, 575, 329-35. (E19) Nakashlma. K.; Makl, K.; Aklyama. S.; Wang. W. H.; Tsukamoto, Y.; Imal, K. Analyst 1989, 774, 1413-6. F. ELECTROCHEMICAL DETECTORS

(Fl) Jandlk, P.; Haddad, P. R.; Stmock, P. E. Crlt. Rev. Anal. Chem. 1988, 20, 1-74.

AiNALYTICAL CHEMISTRY, VOL. 84, NO. 12, JUNE 15, 1992

267R

COLUMN LIQUID CHROMATOGRAPHY (F2) Horval, 0.; Pungor, E. Crk. Rev. Anal. Chem. 1989, 21, 1-28. (F3) Barlscl, J. N.; Wallace, 0. 0. Chim. @gl 1990. 8 , 9-13. (F4) AustlnHanison, D. S.;Johnson, D. C. E&clraenalyss 1989, 7 , 189-97. (F5) Klsslnger, P. T. Lab. Pract. 1989, 38, 67-8. (F6) Lunte, C. E. LC-GC 1989, 7 , 492-4, 496, 498. (F7) Stullk, K. Analyst 1989, 774, 1519-25. (Fa) Buchberger, W. Chromatographia 1990, 30, 577-81. (F9) Ge, H.; Teasdale, P. R.; Wallace, G. G. J. Chromatogr. 1991, 544, 305- 16. (F10) Gorton. L.; Csoergl, E.; Domlnguez, E.; Emneus, J.; Joensson-Pettersson, 0.; Marko-Varga, G.; Persson, B. Anal. Chim. Acta 1991, 250, 203-46. (F11) Lunte, S. M. T r e m Anal. Chem. 1991, 70, 97-102. (F12) Ruban, V. F.; Anlslmova, I. A.; Belen’kll, B. G. J . Chromatogr. 1990, 520, 307-13. (F13) Hoogvllet, J. C.; RelJn, J. M.; Van Bennekom, W. P. Anal. Chem. 1991, 63, 2418-23. (F14) Mslmanga, H. 2.; Sturrock, P. E. Anal. Chem. 1990, 62, 2134-40. (F15) Brearley, T. H.; Doshl, A. K.; Fielden, P. R. Anal. Proc. 1989, 26, 389-90. (F16) Ramstad, T.; Mllner, D. Anal. Inshum. 1989, 78, 147-76. (F17) Ramstad, T. Anal. Left. 1989, 22, 2123-43. (F18) Ruban, V. F. J . H@h Resdut. Chromatogr. 1990, 73, 112-5. (Fl9) Yang, J.; Fang, Q.; Zhang, S. Chln. Chem. Left. 1990, 7 , 113-6. (F20) Zadell, J. M.; MRchell, R.; Kuwana, T. Electroanalysis 1990, 2 , 209-15. (F21) Hua, C.; Sagar. K. A.; Mclaughlln, K.; Jorge, M.; Meaney, M. P.; Smvth. M. R. Analvst 1991. 7 76. 1117-20. (F22) konnor, M. P.;-Wang, J;; Kublak, W.; Smyth, M. R. Anal. Chim. Acta 1990, 229, 139-43. (F23) Nagels, L. J.; Kauffmann, J. M.; Dewaele, C.; Parmentler. F. Anal. Chlm. Acta 1990, 234, 75-81. (F24) Nomura, T.; Yanaglhara, T.; Mttsui, T. Anal. Chlm. Acta 1991, 248, 329-35. (F25j Nagy, T. R.; Anderson, J. L. Anal. Chem. 1991, 63, 2668-72. (F26) Neca, J.; Vespalec, R. J . Chromatcgr. 1990. 574, 161-70. (F27) Vespalec, R.; Neca, J. J . Chromatogr. 1991. 547. 257-64. (F28) Aokl, A.; Matsue, T.; Uchida, I.Anal. Chem. 1990, 62, 2206-10. (F29) Wlghtman, R. M.; May. L. J.; Baur, J.; Leszczyszyn, D.; Krlstensen. E. ACS Symp. Ser. 1989, 403, 114-28. (F30) Ou, T. Y.; Anderson, J. L. J . Elechoanal. Chem. InterfacialElecfrochem. 1981, 302, 1-12. (F31) Johnson, D. C.; Lacourse, W. R. Anal. Chem. 1990, 62, 589A-597A. (F32) Stojanovlc, R. S.; Bond, A. M.; Butler, E. C. V. Anal. Chem. 1990, 62, 2692-7. (F33) Trojanowlcz, M.; Pobozy, E.; Meyerhoff, M. E. Anal. Chlm. Acta 1989, 222, 109-19. ~ ~ i 76, 379-86. (F34) Kublak, W. W. E l 8 C h ~ ~ 1989, (F35) Ramstad, T. Fresenlus’ 2.Anal. Chem. 1989, 335, 493-4. (F36) Luo, P.; Zhang, F.; Baldwln, R. P. Anal. Chlm. Acta, 1991. 244, 169-78. (F37) JI, H.; Wang, E. Talanta 1991, 38, 73-80. (F36) b u r , J. E.;Wightman, R. M. J. Chromatogr. 1989, 482, 65-73. (F39) Ji. H.; He, J.; Dong, S.; Wang, E. J. Elechoanal. Chem. Interfacial Electrochem. 1990, 290, 93-103. (F40) Chi. H.; Wang, Y.; Zhou, T.; Jln, C. Anal. Chim. Acta 1990, 235, 273-7. (F41) Baldwin, R. P.; Thomsen, K. N. Taianta 1991, 38, 1-16. (F42) Wang, E.;JI, H.; Hou, W. Elechoanalyss 1991, 3 , 1-11. (F43) Gunaslngham, H.; Tan, C. 6.; Tan, C. H.; Aw, T. C. J . Chromatogr. S d . 1989, 2 7 , 672-5. (F44) Casella, I. G.; Deslmonl, E.; Cataldl, T. R. I. Anal. Chim. Acta 1991, 248. .., 117-25. . -. . (F45) Elsenberg, E. J.; Cundy, K. C. Anal. Chem. 1991, 6 3 , 845-7. (F46) Hou, W.; Wang, E. Talenta 1991, 38, 557-60. (F47) QI, X.; Baldwin, R. P.; Ll, H.; Guarr, T. F. Elechoanalysis 1991, 3, 119-24. (F48) Zhou, J.; Wang, E. Talenta 1991, 38, 547-55. (F49) Thomsen, K. N.; Baldwin, R. P. Elechoanalyss 1990, 2 , 263-71. (F50) Ou, T. Y.; Anderson, J. L. Anal. Chem. 1991, 63, 1651-8. (F51) Wangsa, J.; Danlelson, N. D. J . Chromatogr. 1990, 574. 171-8. (F52) Sung, J. Y.; Huang, H. J. Anal. Chlm. Acta 1991, 246, 275-81. IF53) Tudos. A. J.: Ozlnoa. W. J. J.: Pome. .. H.: Kok. W. T. Anal. Chem. . 1990, 62. 367-74. (F54) Tudas, A. J.; Ozlnga. A. J. J.; Kok, W. T. J . Chromatogr. 1991, 547,

-

1-10

(F55) .-Lacourse, W. R.; Johnson, D. C. Carbohydr. Res. 1991, 275, 159-78. (F56) Barlsci. J. N.; Wallace, 0. 0. €lechuana/ysls 1989. I , 347-51. (F57) Llsman. J. A.; Underberg, W. J. M.; Llngeman, H. Chromatogr. Sci. 1990, 48, 283-322. (F58) Mako-Varga, 0.; Gorton, L. Anal. Chim. Acta 1990, 234, 13-29. (F59) Smlth, R. M.; Seunders, I.; Abdul, 0. A. J . H/gh ResoM. Chromatogr. 1989, 72, 187-8. (F60) Clos, J. F.; Dorsey, J. G. Anal. Left. 1990, 23, 2327-37. (F61) Berglund, I.;Dasgupta, P. K. Anal. Chem. 1991, 63, 2175-83. (F62) strong,D. L.; Dasgupta, P. K.; Frledman, K.; Stllllan, J. R. Anal. Chem. 1991. 63, 480-6. (F63) Slala, K. J . Chromatogr. 1991, 540, 41-51. (F64) Janecek, M.; Slals, K. J. Chromatogr. 1989, 477. 303-9. (F65) Iwachldo, T.; Hayama, N. Anal. Scl. 1990, 6 , 307-8. (F66) Midgley, D.; Parker, R. L. Taianta 1989. 36, 1277-83. 0 . FLUORESCENCE DETECTORS

(Gl) Van den Beld, C. M. 6.; Lingeman, H. Pract. Spectrosc. 1991, 72, 237-3 16.

268R


(G2) Lingeman, H.; Van de Nesse, R. J.; Brinkman, U. A. T.; Gooljer, C.; Vetthorst. N. H. Methodo/. Swv. Blochem. Anal. 1990, 20, 355-63. (G3) Llngeman, H.; Gooljer, C.; Velthorst. N. H.; R. J.; Brlnkman, U. A. T. Anal. Appl. Spechosc. 1991, 2 , 189-206. (04) Van de Nesse, R. J.; Hoornweg, 0. P.; Gooljer, C.; Brlnkman. U. A. T.; Vehhorst, N. H. Anal. Chlm. Acta 1989, 227, 173-9. (G5) Van de Nesse, R. J.; Gooljer, C.; Hoornweg, 0. P.; Brinkman, U. A. T.; Velthorst, N. H.; Van der Bent, S. J. Anal. Len. 1990, 23, 1235-44. (G6) Van de Nesse, R. J.; Mank, A. J. G.; Hwrnweg. G. P.; Gooljer, C.; Brinkman, U. A. T.; V e b r s t , N. H. Anal. Chem. 1991, 63, 2685-8. (G7) Pfeffer, W. D. Report IS-T-1501; Order No. DE91007666, 1991; 160 PP. (G8) Lee. T.; Yeung, E. S.; Sharma, M. J . Chromatogr. 1991, 565, 197-206. (G9) Ong, C. P.; Ng, C. L.; Lee, H. K.; Ll, S. F. Y. J . Chrometogr. 1991, 559. .- ., 537-45. - . .- .

(G10) Tsunoda, K.; Nomura, A.; Yamada, J.; Nlshl, S. Anal. Chlm. Acta 1980.229.3-7. (G11) Cobb, ’W. T.; McGown, L. B. Appl. Spechosc. 1989, 43, 1363-7. (G12) Cobb, W. T.; McGown. L. 8. Anal. Chem. 1990, 62. 186-9. (G13) Mastenbroek. J. W. G.; Arlese, F.; Gooljer, C.; Velthorst, H. H.; Hofstraat, J. W.; Van Zeljl, W. J. M. Chemosphere 1990, 21, 377-86. (G14) Zhao, 2.; Quan, W. J . Environ. Scl. (China) 1989, 7 , 109-15. (G15) Kleber, D. J.; Blough. N. V. Anal. Chem. 1990, 62, 2275-83. (G16) Kleber, D. J.; Blough, N. V. Free Radlcal Res. Gnnmun. 1990, 70, 109-1 7. (G17) Przyjazny, A.; Bachas, L. 0. Anal. Chim. Acta 1991. 246, 103-12. (G18) Wegrzyn, J.; Patonay, G.; Ford. M.; Warner, I. Anal. Chem. 1990, 62, 1754-8. (Gl9) Cecil, T. L.; Rutan, S. C. J . Chromatogr. 1991, 556, 495-503. (G20) Cecil, T. L.; Poe, R. 8.; Ruten, S. C. Anal. Chim. Acta 1991, 250, 37-44. (G21) TSuda, T.; Noda, H. J . Chromet~gr.1989, 477, 311-9. (G22) Takeuchi, T.; Asano, T.; Ishll. D. J . Chromatogr. 1989, 471, 297-302. (G23) Jalkian, R. D.; Denton, M. B. Roc. SPIE-Int. Soc.Opt. Eng. 1989. 7054, 91-102. (G24) Patel, 9. M.; Moye. H. A.; Welnberger, R. Anal. Len. 1989, 22, 3057-79. (G25) Mawatarl, K.; Ilnuma. F.; Watanabe, M. Anal. Scl. 1990, 6 , 515-8. (G26) Hofstraat, J. W.; Gooljer, C.; Brlnkman. U. A. T.; Velthcfst. N. H. Recent A&. Thin-Layer Chromatoq. [Roc.Chromatogr. Scl. Int. Symp.] 1987. 29-36. (G27) Strojek, J.; Soper, S. A.; Ratzlaff, K. L.; Kuwana, T. Anal. Sci. 1990, 6, 121-9. (G28) Klba, N.; Matsushlta, R.; Oyama, Y.; Furusawa, M. Anal. Chlm. Acta 1991, 248, 367-70. (G29) Kurth, H. H.; Geeb, S.; Turner, W. V.; Kettrup, A. Anal. Chem. 1991, 63, 2586-9. H. INDIRECT DETECTION

(Hl) Yeung, E. S.; Kuhr, W. 0. Anal. Chem. 1991, 63, 275A-276A, 278A. 280A-282A. (H2) Morris, M. D. Chem. Anal. ( N . Y . ) 1989, 707, 361-90. (H3) Rice, P. D.; Thorne, J. 6.; Bobbitt, D. R. Proc. SPIE-Int. Soc. Opt. Eng. 1991, 7435, 104-13. (H4) Pfeffer, W. D.; Yeung, E. S.J . Chromatogr. 1990, 506, 401-8. (H5) Berthod, A.; Glick, M.; Wlnefordner. J. D. J . Chromatogr. 1990. 502, 305-15. (H6) Obrezkov, 0. N.; Shplgun, 0. A.; Zolotov, Y. A.; Shlyamln, V. I. J . Chromatogr. 1991, 558, 209-13. (H7) Oosselet, M.; Sebllle, 8. J. Chromafogr. 1991. 552, 563-73. (H8) Takeuchi, T.; Murayama, M.; Ishll, D. J . H/gh Resolut. Chromatogr. 1990, 73,69-70. (H9) Eppert, G.; Llebscher, G. J. Chrometogr. Scl. 1991, 29, 21-5. (H10) Dorland, P.; Tod, M.; Postalre, E.; Pradeau, D. J . Chromatogr. 1989, 478, 131-40. (H11) Jurklewlcz, K. J . Liq. Chmmatogr. 1989, 72, 2145-69. (H12) Danlelson, N. D.; Wangsa, J.; lones. B. T.; Carlson, J. E. Chromato&?raphia 1990, 29, 139-43. (HI31 Makl, S. A.; Danlelson, N. D. J . Chromatogr. 1991, 542, 101-13. (H14) Makl, S. A.; Danlelson, N. D. Anal. Chem. 1891, 63, 699-703. (H15) Yuan, D.; PletrZyk, D. J. J . Cbmatogr. 1990. 509,357-68. (H16) Pletrzyk, D. J.; Rlgas, P. G.; Yuan, D. J . C h m t o g r . Sei. 1989. 27, 485-90. (H17) Jlang. K. Y.; Llu, M. C.; Zhu. P. L. Chromatcqaphia 1990, 29, 131-4. (H18) Mehra, M. C.; Pelletler, C. Chmnatopaphia 1990, 30, 337-8. (H19) Mehra, M. C.; Pelletler, C. Anal. Scl. 1990, 6 , 431-4. (H20) Wangsa, J.; Targove, M. A.; Danlelson, N. D. Telanta 1990, 37. 1151-4. (H21) Walker, T. A.; Ho, T. V.; Akbari, N. J . Liq. Chmatogr. 1988, 72, 1213-30. 0422) Walker. T. A.; Ho, T. V.; Akbarl, N. J. U q . Cfwomatogr. 1981, 74. 11351-66. (H23) Walker, T. A,; Ho, T. V. J . Chromatogr. Scl. 1990. 28, 254-7. (H24) Walker, T. A.; Akbarl, N.; Ho, T. V. J. Llq. Chmatogr. 1991, 74, 619-41. (H25) Pletrzyk, D. J.; Senne, S. M.; Brown, D. M. J. C h r o m a w . 1991, 546, 101-10. (H26) Pacakova, V.; Stullk, K.; Wu, M. J . Chromatogr. 1990, 520, 349-59. I . INFRARED DETECTORS

(11) Grlfflths. P. R.; Mefner, A. M.; Norton, K. L.; Fraser, 0.J. J.; Pyo, D.; Maklshlma, H. J . High Resdut. Chromatogr. 1989, 12, 119-22. (12)1991, Norton, K. L.; Lange, A. J.; Grlffiths, P. R. J . Hm Res&. chrometogr. 74, 225-9.

COLUMN LIQUID CHROMATOGRAPHY (13) De Haseth. J. A.; Robertson, R. M. Mlcrochem. J . 1989, 40, 77-93. (14) Robertson, R. M.; De Haseth, J. A.; Browner, R. F. Appl. Spectrosc. 1990, 44, 8-13. (15) Jlnno. K.; Fujlmoto, C. J . Chmmatogr. 1990, 506, 443-60. (16) Fujlmoto, C.; Jlnno, K. TrAC, Trends Anal. Chem. 1989, 8 , 90-6. (17) Ract. Spectrosc. 1990. 70, 95-138. (18) Saker, R.; Meyer, U. Teubner-Texte phvs. 1988, 20, 39-53; Chem. Abstr. 1990, 772, 47963~. (19) Busch, K. W.; Hudson. K. M.; Bwch. M. A.; Kubala, S. W., Jr.; THotta, D. C.; Lam, C. K. Y.; Srlnlvasan, R. PCT Int. Appl. WO 9105241 Al, 18 April 1991. 168 pp. (110) Lange, A. J.; Grlfflths, P. R.; Fraser, D. J. J. Anal. Chem. 1991, 63, 782-7. (111) Fraser, D. J. J.; Norton, K. L.; Grlffiths, P. R. Anal. Chem. 1990, 62, 308-10. (112) Jlnno, K.; Fujlmoto, C. hog. H R C 1989, 4 , 273-96. (113) Huber, S. A.; Frlmmel, F. H. Anal. Chem. 1991, 83, 2122-30. (114) Jansen, J. A. J. Fresenlus’ J . Anal. Chem. 1990, 337, 398-402. (115) Robertson, A. M.; Wylle, L.; Littlejohn, D.; Watllng, R. J.; Dowle. C. J. Anal. Roc. (London) 1991, 28, 8-9. (116) Shah, S.; Ashraf-Khorassanl, M.; Taylor, L. T. ChfOmatogf8phIa 1989. 27, 441-8. J. LClMS (Jl) Burllngame, A. L.; Milington, D. S.; Norwood, D. L.; Russell, D. H. Anal. Chem. 1990, 62, 268R-303R. (J2) Ishll, D.; Takeuchl, T. Trends Anal. Chem. 1989, 8 , 25-9. (J3) Huang, E. C.; Wachs, T.; Conboy, J. J.; Henlon, J. D. Anal. Chem. 1990, 62, 713A-722A, 724A-725A. (J4) Bruins, A. P. A&. Mass Spectrom. 1889, 77A, 23-31. (J5) . . Nlessen. W. M. A.; Tiaden, U. R.; Van der Greef, J. J . Chromatogr. 1991, 554, 3-28. (J6) Van der Grwf, J.; Nlessen, W. M. A.; Tjaden, U. R. J. Chromatogr. lPB8. .- - -, 474. . . . , 5-19. . . (J7) Arplno. P. Mass Specfrom. Rev. 1990, 9 , 631-69. (J8) Roboz, J.; Hdland, J. F.; McDowell, M. A.; Hlllmer. M. J. RapMCommun. Mass Spectrom. 1988, 2 , 64-8. (J9) Gegne, J. P.; Cerrkr, A.; Bertrand, M. J. J . Chromatogr. 1991, 554, 47-59, (J10) Kokkonen, P.; Schroeder, E.; Niessen, W. M. A.; Tjaden, U. R.; Van der Greef, J. J. Chromatogr. 1990, 577, 35-47. (J11) Kokkonen, P.; Van der Greef, J.; Schroeder, E.; Nkssen, W. M. A.; Tjaden, U. R. Org. Mass Spectrom. 1990. 25, 586-8. (J12) Heeremans, C. E. M.; Van der Hoeven, R. A. M.; Nlessen, W. M. A.; Tjaden, U. R.; Van der Grwf, J. J. Chromatogr. 1988, 474, 149-62. (J13) Robins, R. H.; Crow, F. W. Rapid Commun. Mass Spectrom. 1988, 2 . 30-4. (J14) GenuA, W.; Van Blnsbergen, H. J. Chromatogr. 1988, 474, 145-8. (J15) nnke, A. P.; Heeremans, C. E. M.; Van der Hoeven, R. A. M.; Nlessen, W. M. A.; Van der Greef, J.; Nibbering, N. M. M. Rapid Commun. Mass Spectrom. 1991, 5 , 188-91. (J18) Ozakl, E.; Mlzuno, T.; Otsuka, K. J . Hlgh Resolut. Chromatogr. 1991, 74, 215-6. (J17) Kaiser, R. E., Jr.; Wllllams, J. D.; Lammert, S. A.; Cooks, R. G.; Zakett. D. J . ChrOMtOgr. 1991, 562, 3-11. (J18) Nlessen, W. M. A.; Van der Hoeven, R. A. M.; De Kraa, M. A. G.; Heeremans, C. E. M.; Tjaden, U. R.; Van der Greef, J. J . Chromatogr. 1988, 474, 113-22. (J19) Nlessen, W. M. A.; Van der Hoeven, R. A. M.; De Kraa, M. A. G.; Heeremans, C. E. M.; Tjaden, U. R.; Van der Greef, J. J. Chromatogr. 1989, 478, 325-38. (J20) Heeremans, C. E. M.; Van der Hoeven, R. A. M.; Niessen, W. M. A.; Van der Beef, J.; Nlbberlng, N. M. M. 0 8 .Mass Specfrom. 1991, 26, 519-27. (J21) Sanders. P. E. Rapid Commun. Mass Spectrom. 1990, 4 , 123-24. (J22) Baczynskyj. L. Rapid Commun. Mass Spectrom. 1990, 4, 198-201. (J23) Ligon. W. V., Jr.; Dorn, S. 8. Anal. Chem. 1990, 62, 2573-80. (J24) Gegne, Jean-Plere; Roussis. S. G.; Bertrand, M. J. J . Chromafogr. 1991, 554, 293-304. (J25) Apffel. A.; Perry, M. L. J. Chromatogr. 1991, 554, 103-18. (J26) Tlnke, A. P.; Van der Hoeven, R. A. M.; Nlessen, W. M. A,; Tjaden. U. R.; Van der Qlwf, J. J. Chromatogr. 1991, 554, 119-24. (J27) Hhadta, K.; Kudaka, I . RapM Commun. Mass Specfrom. 1990, 4 , 519-26. (J28) Ikonomou, M. G.; Blades, A. T.; Kebarle, P. Anal. Chem. 1990, 62, 957-87. (J29) Emary, W. B.; Lys, I.; Cotter R. J.; Simpson, R.; Hoffman, A. Anal. Chem. 1990. 62, 1319-24. (J30) Slmpson, R. C.; Emary, W. 8.; Lys, I.; Cotter, R. J.; Fenselau. C. C. J . C h r ~ @ l f 1991, . 536, 143-53. (J31) Mcluckey, S. A.; Van Berkel, 0. J.; Gllsh, G. L.; Huang, E. C.; Henlon, J. D. Anal. Chem. 1991, 63, 375-83. (J32) Henlon, J.; Lee, E. Ract. Spectrosc. 1990, 8 . 489-503. (J33) Slmpson, R. C.; Fenselau, C. C.; Hardy, M. R.; Townsend, R. R.; Lee, Y. C.; Cotter, R . J. Anal. chem. 1990, 62, 248-52. (J34) Conboy, J. J.; Henlon, J. D.; Martin, M. W.; Zwelgenbaum, J. A. Anal. Chem. 1990, 62, 800-7. (J35) Asakawa, N.; Ohe, H.; Tsuno, M.; Nezu, Y.; Yoshida, Y.; Sato, T. J . chrometoby. 1991, 547, 231-41. (J36) Kokkonen, P. S.; Niessen. W. M. A.; Tjaden, U. R.; Van der Greef, J. RapHCOmmun. Mss Spectrom. 1991. 5 , 19-24. (J37) Babgh, M. P.; Stacey, C. C. J . Chromatoby. 1991, 562, 73-9. (J38) m a , H.; Ikai, Y.; Kawamwa, N.; Hayakawa, J.; Harada, K.; Murata. H.; Suzukl. M.; Ito, Y. Anal. Chem. 1991. 63, 2861-5. (J39) Lee, Y. W.; Voyksner. R. D.; Pack, T. W.; Cook, C. E.; Fang, Q . C.; Ito, Y. Anal. Chem. 1990. 62, 244-8.

(J40) Molnl. M.; Abramson, F. P. Bbl. Mass. Specfrom. 1991. 20. 308-12. (J41) Heltkemper, D.; Creed, J.; Caruso, J. A. J . chrometogr. Scl. 1990, 28, 175-81. (J42) Mason, A. 2.; Storms. S. D.; Jenkins, K. D. Anal. Bkchem. 1990, 786, 187-201. (J43) Kawabata, K.; Kishl. Y.; Kawaguchi. 0.; Watanabe, Y.; Inoue, Y. Anel. Chem. 1991, 63,2137-40. K. OPTICAL ACTIVITY DETECTORS

(Kl) Vos, J. N.; Kat-Van den Nleuwenhof, M. W. P.; Basten, J. E. M.; Van Boeckel, C. A. A. J . Carbohydr. Chem. 1990. 9 , 501-5. (K2) Lloyd, D. K.; ooodall, D. M. ChhI/ty 1989, 1 . 251-64. (K3) Kawazuml, H.; Nlshimura, H.; Ogawa, T. Anal. Scl. 1990, 6 , 135-8. (K4) XI, X.; Yeung, E. S. Anal. Chem. 1991, 63, 490-6. (K5) Kawazuml, H.; Nlshimura, H.; Otsubo, Y.; Ogawa, T. T8Ianta 1981. 38, 965-9. (K6) Xu, M.; Tran, C. D. Anal. Chem. 1990. 62, 2467-71. (K7) Bertuccl, C.; Domenlci, E.; Salvadorl, P. J . h r m . E M . Anal. 1990, 8, 843-6. (K8) Kurosu, Y.; Sasakl. T.; Takakuwa, T.; Sakayanagl, N.; Hlbl, K.; Senda, M. J . Chromatogr. 1990. 575, 407-14. (K9) Yamamoto. A.; Matsunaga. A.; Hayakawa, K.; Mlzukaml, E.; Mlyazakl, M. Anal. S a . 1991, 7 , 719-21. (K10) Wu, 2.; Goodall, D. M.; Lloyd, D. K.; Massey, P. R.; Sandy, K. C. J. ChrOMtOgr. 1990, 573, 209-18. (K11) Mannschreck, A.; Klessl, L. Chromatographla 1989, 28, 263-6. (K12) Rice, P. D.; Shao. Y. Y.; Bobbltt, D. R. Talanta 1989, 36, 965-8. (K13) Ng, K.; Rice, P. D.; Bobbitt, D. R. Mlcrochem. J . 1991, 4 4 , 25-33. (K14) Heyraud, A,; Rlnaudo, M. ACS Symp. Ser. 1991, 458, 171-88. L. REFRACTIVE INDEX DETECTORS (Ll) Bruno, A. E.; Krattlger, B.; Maystre, F.; WMmer, H. M. Anal. Chem. 1991, 63, 2689-97. (L2) Welgang, F.; Relter, M.; Jungbauer. A.; Katlnger, H. J . Chromatogr. 1989, 497, 59-68. (L3) Masson, S.; Sclaky, M.; Desmoulin, F.; Fontanarava, E.; Couone, P. J. J . Chromatogr. 1991, 563, 231-242. (L4) Vaccher, C.; Berthelot, P.; Flouquet, N.; Debaert, M. Ann. h r m . Fr. 1990, 48, 264-272; Chem. Abstr. 1991, 714, 129232d. (L5) Hancock. D. 0.; Renn, C. N.; Synovec, R. E. Anal. Chem. 1990, 62, 2441-7. (L6) Renn, C. N.; Synovec, R. E. J . Chromatogr. 1991, 536, 289-301. (L7) Synovec, R. E.; Renn. C. N. Roc. S f I € - I n t . Soc.Opt. €ng, 1991, 7435, 128-39. M. MISCELLANEOUS DETECTORS

(Ml) Marshall, W. D.; Blals, J. S.; Adams, F. C. NATOASI Sw., Ser. 43 1990, 23, 253-73. (M2) Weber, B.; Berndt, H. Chromatographla 1990. 29, 254-8. (M3) Stupar, J.; Frech, W. J. Chromatogr. 1991, 547. 243-55. (M4) Blals, J. S.; Momplalslr, 0. M.; Marshall, W. D. Anal. Chem. 1990. 62, 1181-6. (M5) Blals, J. S.; Marshall, W. D. J . Anal. At. S p e c f ” . 1989, 4 , 641-5. (ME) Lewis, V. D.; Nam, S. H.; Urasa, I . T. J . Chromatogr. Scl. 1989, 2 7 , 468-73. (M7) Roychowdhury, S. B.; Koropchak, J. A. Anal. Chem. 1990, 62, 484-9. (ME) Elgersma, J. W.; Balke, J.; Maessen, F. J. M. J. Specfrochh. Acta, Pari B 1991, 468, 1073-88. (M9) Pomeroy, R. S.; Kolczynskl, J. D.; Denton, M. B. Appl. Spectresc. 1991, 45. 1111-9. (M10) Walton, A. P.; Wel, 0. T.; Llang, 2.; Michel, R. G.; Morris, J. B. Anal. Chem. 1991, 63.232-40. ( M l l ) Zolotov, Y.; Petrukhln, 0. M.; Tlmerbaev, A. R.; Evstlferov. M. V.; Salov, V. V.; Vanlfatova, N. 0. Analyst (London) 1989, 774, 1337-9, (M12) Berezlkln, V. G. C&. Rev. Anal. Chem. 1989, 2 0 , 291-318. (M13) Malcolme-Lawes, D. J.; Moss, P. J . chrometogr. 1989, 482, 53-64. (M14) McMlnn, D. 0.; Klnzer, J. A.; Shumate. C. B.; Slems, W. F.; HIII, H. H., Jr: J. Mlcrocolumn Sep. 1980. 2 , 188-92. (M15) Drew, M.; Lafosse, M. Specbg 2000 [oeU*Mk] 1990, 753,2432. (M16) Dreux, M.; Lafosse, M. Spectra 2000 [Dwx AM&] 1990, Suppl. 151, 16-21. (Mlf -Mngerlnk, Y.; De Man. H. C. J.; Van der Wal, S. J . chrometcgr. 1991, 552, 593-604. (M18) Elfakir, C.; Lafosse, M.; Drew, M. J . Chrometog. 1990, 573. 354-9. (M19) Stockwell. P. B.; King, B. W. Am. Lab. 1991, 23. 19-20. 22-4. (M20) Lutzkl. 8. S.; Braughler, J. M. J . UpM Res. 1990, 37. 2127-30. (M21) Drogue, S.; Rolet, M. C.; Thlebaut, D.; Rosset, R. J . chrometoby. 1991, 538, 91-7. (M22) Claes, P.; Fowell, S.; Wwllin, C.; Kenney A. Am. Lab. 1990. 22, 58, 60, 62. (M23) Suck, T. A. LaborpIexls 1990, 14, 776, 116-9, (M24) Grenlerloustalot, M. F.; Grenier, P.; Bounoure, J.; Grail, M.; Panaras, R. Analusls 1990, 78, 200-7. (M25) I@, M.; Maier-Rosenkranz, J.; Mueller, W.; Baeyer, E. J . chromatog. 1990. 577. 283-8. (M26) Frankel, E. N.; Neff. W. E.; Welsleder, D. Methods E n z y d . 1990, 186, 380-7. (M27) Shiragaml. N. Bioprocess €ng. 1990, 5 (3). 115-7. (M28) Prognon, P.; Cepeda. A.; Sargl. L.; Blsagnl, E.; Mahuzier, 0. Anakgk 1990. 78, 1-8. (M29) Campiglie, A. D.; Berthod, A.; Wlnefordner, J. D. J. Chromatogr. 1990. 508. 37-49. (M30) Voigtmn. E.; Snyder, P. A. Anal. Insbum. 1990, 79. 1-13. (M31) S d r m u n d , J. T.; Locke, D. C. J . CXromatcgr.1990, 505, 319-28. (M32) Miles, C. J.; Zhou, M. J . Agrlc. FoodChem. 1990. 38, 986-9. ’


269R

Anal. Chem. 1002, 64, 270 R-302 R (M33) Bachman, W. J.; Stewart. J. T. J . Chfomatcgr. 1989, 481, 121-33. (M34) Turk, 0.C.; Kinsgton, H. M. J . A M I . At. Speclrom. 1990, 5 , 595-801. (M35) Qulnt, J.; Newton, J. F. Rugs Mann. S d . 1991, 47, 101-22. (M38) Relch, A. R.; Lucas-Reich, S.; Parvez. H. hog. HPLC 1988, 3 , 1-10. (M37) Vekamp. A. C.; Des. H. A,; Frei, R. W.; Brinkman, U. A. T. A M I . Chim. Acta 1900, 233, 181-9. (M38) Bradbury, D.; Elder, 0. R.; Dunn, M. J. hoc. Symp. Waste Menage. 1990, 2 , 327-9. (M39) Baldew, G. S.; De Goeij, J. J. M.; Vermeulen, N. P. E. J . Chromtogr. 1989, 498, 111-20. (M40) Rustum. A. M.; Ash, S.; Saxena, A.; Balu, K. J . Chmmtcgr. 1990, 514, 209-18.

(M41) Thelmer, K. H.; Krhran, V. Anal. Chem. 1090, 82, 2722-7. (M42) Smith, A. D.; oiiiis, K. M.; Ludden, J. N. chsm. W. 1990, 81, 17-22. (M43) Cotton, T. M.; Sheng, R.; NI, F. proc. SPE-Int. Soc. opt. Eng. 1990, 1336. 280-90. (M44) Sheng, R.; Ni. F.; Cotton, T. M. Anal. Chem. 1991, 83, 437-42. (M45) Ni. F.; Stteng, R.; Cotton, T. M. Anal. Chem. 1990, 82, 1958-83. (M48) Pothler, N. J.; Force, R. K. Anal. Chem. 1990, 82, 878-80. (M47) Soper, S. A.; Ratzlaff. K. L.; Kuwana, T. Anal. Chem. 1990. 62, 1438-44. (M48) Dutta, P. K.; Hammons, K.; Willibey, 6.; Haney, M. A. J . chrometogr. 1991, 538, 113-21. (M49) Yau, W. W. C. Eur. Pat. Appi. EP 380864 A2, 8 Aug. 1990; 9 pp.

Infrared Spectrometry Curtis L. Putzig,* M. Anne Leugers, Marianne L. McKelvy, Gary E.Mitchell, Richard A. Nyquist, Richard R.Papenfuss, and Lori Yurga Analytical Sciences Laboratory, 1897 Building, The Dow Chemical Company, Michigan Division, Midland, Michigan 48667

INTRODUCTION This review covers the published literature for the period late 1989 to late 1991 on aspects of infrared spectrometry that are relevant to chemical analysis. Our review has a strong bias toward papers published in English, or in certain aspects of IR spectrometry that are of particular interest to one or more of the coauthors. In addition, a few selected references to FT-Raman spectrometry are included for reasons given below.

which are strong in the Raman are usually weak in the IR, and vice versa in cases where the normal modes are allowed in both vibrational techniques. With the recent development of Fourier transform Raman (FT-Raman),it is now possible to rapidly record Raman spectra of most materials by using the FT-IR system equi ed with the FT-Raman option. FT-Raman is commercig available from several manufacturers, and we predict that in the future both IR and Raman ra will be recorded of materials on a routine basis for the e ucidation and identification of molecular structure. Therefore, we have included a few selected references to FT-Raman spectrometry for your convenience.

OVERVIEW OF ANALYTICAL INFRARED SPECTROMETRY Infrared radiation is usually defined as that electromagnetic radiation whose fre uency is between 14300 and 20 cm-’ (-0.7 and 500 pm). bithin this region of the electromagnetic ,chemical compounds absorb IR radiation providing t ere is a dipole moment change during a normal molecular vibration, molecular rotation, molecular rotation-vibration, or a lattice mode or from combination, difference, and overtones of the normal molecular vibrations. The frequencies and intensities of the IR bands exhibited by a chemical compound uni uely characterize the qaterial, and-its IR spectrum can be use! to identlfy and quantify the particular substance in an unknown sample. Different classes of chemical compounds contain chemical oups which absorb IR radiation at essentially identical requency(ies) and have essentially the same band intensity(ies) wthin each class of compound, and these bands are termed “group frequencies”. Group frequencies are predictable and allow the anal t to elucidate and identify molecular structures without a v z b l e IR standard reference spectra for comparison. In addition IR spectra can be recorded ra idly of materials in the solid, liquid, solution, and vapor p ases over a wide range of temperature. Such studies aid in elucidatin the molecular structure of materials in different physic3 phases. Toda modern IR instrumentation allows spectra to be recorddof aam lea available in only low nanogram quantities or as low as hig picogram quantities using matrix isolation techni ues. No other technique allows examination and identdcation of materials under such a wide variety of hysical conditions, and it is this versatility that has allowed spectrometry to develop into the “work horse” of analytical science. One should be aware of the fact that Raman spectrometry is a complementary technique to IR spectrometry. In cases where a chemical compound has a center of symmetry,certain normal vibrations will only be active in the Raman and certain normal vibrations will only be active in the IR. Thus, one needs both techniques to record the com lete vibrational spectrum of many chemical compounds. horeover, bands

-

(A) BOOKS Lin-Vien et al. have published a timely and excellent book integrating the characteristic IR and Raman fre uencies of organic molecules ( A I ) . Duri edited books for t e applications of FT-IR spectrosco y fA2) and advances in the field of vibrational s ectra anzstructure (A3). George and #illis edited a book on com uter methods for UV, visible, and IR spectroscopy (A4). collection of IR spectra of common solvents has been published (A5). n edited a book on IR technology and a lications (A$%%% edited a book on chromatography/#IR ( A n Ferraro and Krishman edited a book on the application of FT-IR for industrial and laboratory chemical analysis (A8). Suzuki et al. edited a book on IR and Raman data base for the period June 1988 to May 1989 (A9).

1

1

(B) REVIEWS A review of IR spectrometry covering the period 1985 to late 1989 has been ublished (BI). The review on polymer analysis including and Raman spectrometry covering the period December 1988 to November 1990 has been published (B2). Urban reviewed the literature on photoacoustic FT-IR of polymers with emphasis on the dynamics of small molecules in olymer networks and interfacial interaction (B3). Takeand Umenura reviewed the application of IR and Raman spectroscopyto the study of surface chemistry with emphasis on surfactantsand their aqueous solutions,films, and adsorbed molecules at g-lid and liquid-solid interfa- (B4).%lea and Von Nagy-Felsoluki reviewed the ab initio calculations of vibrational band origins (B5).Scheiner reviewed the ab initio studies of the structure, energetics, and vibrational spectra of hydrogen bonded systems (B6). Davidson reviewed the characteristic vibrations of compounds containing the main-group elements I through VI11 (B7). Duncan reviewed the o of vibrational anharmonicity in molecules and the e f f e c t s x t the vibrational resonances have on the anharmonicity constants which may be extracted

K

&

E

&

fk

270 R

0003-2700/92/0384-270R$10.00/0

0

1992 American Chemical Society

Column liquid chromatography: equipment and ... - ACS Publications

Recommend Documents