Anal. Ckem. 1994,66, 1R-16R
Column Liquid Chromatography: Equipment and I nstrumentation Carsten A. Bruckner, Marc D. Foster, Lawrence R. Llma, 111, and Robert E. Synovec' Center for Process Analytical Chemistry, Department of Chemistry, B G IO, University of Washington, Seattle, Washington 98 195 Rlchard J. Berman, Curtlss N. Renn, and Edward L. Johnson' ALPKEM Corporation, 9445 Southwest Ridder Road, Suite 3 IO, Wilsonville, Oregon 97070 Review Contents Columns Packing Techniques Maintenance and Troubleshooting Instrumentation Pumps/Valves/Systems Automation/Hyphenated Techniques/Sample Preparation Chemometrics Detectors Absorbance Detectors Chemiluminescence Detectors Electrochemical Detectors Reviews and Comparative Studies New Detectors New Electrodes Novel Electrochemical Applications Fluorescence Detectors Indirect Detection Infrared Detectors LC/MS Reviews of the Field Fast Atom Bombardment (FAB) Thermospray Particle Beam (PB) Ion Spray Electrospray Atmospheric Pressure Ionization (API) ICP-MS and Plasma Spray Miscellaneous Topics of Interest Optical Activity Detectors Refractive Index Detectors Miscellaneous Detectors Atomic Absorbance Spectrometry (AAS) Atomic Emission Spectrometry (AES) Degenerate Four-Wave Mixing (D4WM) Ion Mobility (IM) Light Scattering (Evaporative) Molecular Size (Light Scattering) Detector Nuclear Magnetic Resonance (NMR) Radioactivity Raman Thermionic (Nitrogen/Phosphorus) Viscometry
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This review covers the fundamental developments in the field of column liquid chromatography (LC), dealing with equipment and instrumentation, during the period 1992-1993. Our main data base for this review was CA Selects from 0003-270009440360-0001$14.00~0 0 1994 American Chemical Society
December 1991 through October 1993. The literaturesearch includedmanuscripts, patents, and theses published in English, French, German, Japanese, and Russian, with some exceptions. This review is not a comprehensive coverage of all L C literature dealing with equipment and instrumentation. Rather, the review reflects our critical selection of fundamental develop ments in this field of LC. For this reason, patents and theses were considered, although manuscripts dominate the coverage. Your suggestions and comments should be addressed to the senior authors (E.L.J. and R.E.S.). Reprint requests should be made to R.E.S. This review is organized with the following sections: A, Columns; B, Instrumentation; C, Detectors; D, Absorbance Detectors; E, ChemiluminescenceDetectors; 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 many of the sections.
A. COLUMNS This section of the review will be divided into two parts, covering references on packing techniques and references on maintenance and troubleshooting. Packing Techniques. During this review period most reported work focused on new techniques to improve microHPLC columns. Cappiello and co-workers ( A I ) described the use of '/16-in.-o.d. PEEK tubing and appropriate new packing techniques. Dry packing techniques for capillary columns were described Guan and co-workers (A2). A modified technique for the preparation of 320-~m4.d.columns is claimed to have excellent reliability in the production stage, as described by Baechmann, Haag, and Prokop (A3). Open tubular columns modified with chemically bonded C18 moieties are described by Crego and co-workers ( A ) .Perry and Szczerba (AS) discuss a technique for comparing the performance per cost for preparative-scale columns. Maintenance and Troubleshooting. Rodrigues and coworkers (A@ prepared a review on large-pore materials used in chromatography and other separation processes. They emphasize the importance of mass transport by intraparticle forced convection. Porsch (A7)reviews a variety of experiences with amino phases. The stability and performance of a new anion-exchange material are described by Su, Li, and Hu (A8). Chen and co-workers (A9) describe an extensive study Ana&ticalChemistry, Vol, 66, No. 12, June 15, 1994
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Carsten A. Bruckner is a graduate student in Analytical Chemistry at the University of Washington. He received his B.S. in chemistry at the Universityof NorthCarolina in Chapel Hill (1992) and was the recipient of the Whitaker and Gannett Scholarships. His interests include the use of novel optical detection schemes for GC and LC. He is currently working on a system that has applications in sample preparation, separation, and detection.
Marc Foster is a graduate student at the University of Washington. He received his B.S. degree in chemistry from the California State University in Sacramento in 1987. Before beginning graduate work in 1991, he was employed at Progressive Circuit Products, where he monitored wet chemistry processes, supervised the waste treatment facility, and developed new techniques for waste minimization and environmental compliance. His research interests include process analysis and control, environmental monitoring methods, and chromatographic detection instrumentation and techniques. Lawrence R. Lima, 111, is a graduate student in Analytical Chemistry at the University of Washington. He received his B.S. in chemistry at Harvey Mudd College, Claremont, CA (1989) and was awarded the ACS Undergraduate Award in Analytical Chemistry in 1988. His research interests include analytical development for process chemistry, chromatographic methodology development for complex matrix analysis, and development of detectors for chromophore-lacking analytes.
Robert E. Synovec is currently an Associate 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 198 1, 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 an AlDha Chi Siama Graduate Award (1984). an ACS ResGarch 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 chromatography separation, detection, and quantitation techniques for either bench-top or process analysis, high-speed, hightemperature, 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.
of the S index, which is used to estimate solute retention in reversed-phase liquid chromatography. The impact of metal impurities in packing materials and their subsequent impact on the observed chromatography are described by Kimata and co-workers (AZO). Techniques for evaluating the homogeneity of columns are described by Macko and Berek ( A I I). Maruska and co-workers (A22) reported studies dealing with the morphological structure and its influence in 2R
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Richard 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 Universityof Washington in 1990 under the direction of Dr. Gary D. Christian and Dr. Lloyd W. Burgess. The subject of his dissertation researchwas 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. Curtlss N. Renn 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 Universityof Washington in 199 1under the direction of Assistant Professor Robert E. Synovec. He received the Battelle Northwest (1989) and the Dow -.- - - Fellowship . -. .- - Outstanding Graduate Student Award (1989) while pursuing a Ph.D. at the University of Washington. His research interests include laser-based detectors for microbore LC, multiwavelength fiber-optic detectors for microflow systems (LC and FIA), high-speed and hightemperature 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 L. Johnson is currently president of ALPKEM Corp., 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 held a variety of positions during a 10-year period with Dionex Corp. in Sunnyvale, CA. The final position was Vice President of Technology. He served as a Senior Applications Chemist with Varian for 2 years, where he coauthored the book Basic Liquid Chromatography. As a Senior Research Chemist at Goodyear Tire & Rubber Co. in Akron, OH, he developed more than 100analytical methods. He has published numerous papers dealing with both liquid and ion chromatography. He was co-inventor for eight 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.
the GPC results. An article about scale-up problems of SEC with compressible packings has been reported by Mohammad and co-workers (A23). Models that accurately describe retention in reversed-phase chromatography as a function of pH and composition have been reported by Lopes and coworkers (AZ4). Computationaltechniques were used by Hanai and co-workers to study the best form of silica gel for the preparation of column packings (AZ5). Horvath and coworkers (A26)reported on the effect of intraparticleconvection in columns packed with gigaporous particles. Wilson and Simmons reported a particle size distribution and SEM study of used RPLC columns (AZ7). A simple technique for estimating the degree of flow profile distortion in a preparativescale column was described by Kaminski (A28). Tuning the selectivity of serially coupled columns is discussed in an interesting study by Welsch and co-workers (AZ9).
B. INSTRUMENTATION This section of the review focuses on new developments in the area of column liquid chromatography equipment, advances in hyphenated LC techniques, and developments in LC data analysis. The number of application papers for LC has steadily risen as the need for chemical information has increased in the environmental analysis and biomedical fields. Specifically, the number of reports of automated and robotics applications with LC continues to rise to meet theneed for higher laboratory throughput. However, since most of the reports on LC automation and robotics are of an applications nature, application-oriented papers will not be included in this review. Only significant advances or novel implementation of robotics or automation techniques are cited. During the period of this review, Papoff and co-workers ( B I ) presented a review of ion chromatography instrumentation and methodologies for environmental and industrial use. Brinkman ( 8 2 )published a review of LC sample pretreatment. A review with 40 references for the separation of biochemical species via hydrodynamic and hydrostatic high-speed countercurrent chromatography was published by Thiebaut and Rosset (B3). A review with 117 references on the principles and application of countercurrent chromatography was presented by Ito (B4). Reviews of hyphenated sample pretreatment via membrane technology for LC were reported by Joensson and Mathiasson (B5)and Verillon and Qian (B6). FIA coupled with LC was reviewed by Luque de Castro and Valcarcel ( B 7 ) . Poppe (B8)presented an extensive review of LC hardware and optimization techniques with 135 references. Pumps/Valves/Systems. Yamamotoand co-workers (B9) demonstrated the use of electroendosmotic flow as a pumping mechanism for packed-capillary LC. The effect of the injection solvent on injection profile and peak retention was investigated by Johnson and co-workers (BIO), Grob and co-workers ( B I I ) , and Lee and Hoffman (BIZ).A modulated rectangular injection input function was demonstrated by Louwerse and co-workers ( B I 3 ) as an intermediate method between single-injection and correlation chromatography. A novel process for combining and analyzing streams from multiple columns for separation and quantitation was described by Hatanaka and Ishida ( B I 4 ) . Cretier and co-workers (BJ5) determined optimum injection conditions for gradient separations in preparative chromatography. Liu, Djordjevic, and Erni (BI6)developed an LC system for high-temperature separations using a 100-pm open tubing capillary column. Efficienciesas high as 1.1 million theoretical plates were measured at a separation temperature of 200 "C. Miura and co-workers (BI7)developed a capillary LC system on a chip with sample introduction and provisions for field effect transistor detection. An industrial process LC system with capability for selfdiagnostics was developed by Guillemin (BI8). Ohara and co-workers (BI 9 ) developed and applied an automated HPLC system for monitoring lactic acid fermentation. Automation/Hyphenated Techniques/Sample Preparation. Aerosol-phase extracolumn effects due to interfacing LC with various detectors were investigated by Koropchak and coworkers (B20).A solvent-vented interface for coupling size-
exclusion LC with capillary supercritical fluid chromatography
was evaluated by Moulder and co-workers (B21). Engelhardt, Zapp, and Kolla (B22) demonstrated on-line coupling of supercritical fluid extraction with solventless injection into capillary supercritical fluid chromatography. Isobe and coworkers (B23)developed an automated two-dimensional L C system for protein separations that was used for mapping proteins in complex media. The system was demonstrated by separation of over 200 peaks derived from crude cerebellar extraction. Tena and co-workers (B24) integrated a flow injection system with HPLC for total and individual determination of carbamate pesticides. Sample preparation and integration of LC with gas chromatography were reported (B25,B26) during the review period. Sample preparation, cleanup, and direct coupling of LC to overpressure layer chromatography were demonstrated by Mincsovics, Garami, and Tyihak (B27). Debets and coworkers (B28)implemented on-line electrodialytic sample treatment to gain a 10-20-fold factor of selective enrichment for detection of herbicides in ground water. Andresen and co-workers (B29)coupled on-line dialysis and column switching for automated LC analysis of iopentol in human plasma and whole blood. Brewster, Maxwell, and Hampson (B30) employed an on-line membrane interface to remove carbon dioxide from supercritical fluid extraction before injection into a flowing system such as L C or flow injection analysis. Bao and Dasgupta (B31) developed a membrane interface utilizing on-line preconcentration for sample introduction into capillary zone electrophoresis. Chemometrics. Guillemin (B32)presented the groundwork for intelligent process chromatographic systems yielding predictive maintenance information. Li and co-workers (B33) investigated the use of a similarity transformation with the generalized rank annihilation method to estimate spectra and profiles of pure components when complex eigenvalues and eigenvectors are encountered. The effect of detector nonlinearity on principal component analysis for photodiode array detection in LC was investigated by Keller and co-workers (B34). Bahowick and Synovec (B35) utilized the method of sequential chromatogram ratios to evaluate the effects of retention time precision, adsorption isotherm linearity, and detector linearity on qualitative and quantitative analysis in LC. A peak recognition technique was developed by Waetzig (B36) that is adapted from human judgments. Peterson (837) investigated the use of counterpropagation neural networks for modeling and prediction of Kovats indexes of substituted phenols.
C. DETECTORS New developments in detection technology for liquid chromatography continue to focus on meeting the requirements imposed by capillary and microbore column dimensions, as reviewed by Jorgenson and De Wit (CI). In another review by Fielden (CZ),recent developmentsin liquid chromatography detector technology were evaluated and broadly classified into the areas of spectroscopic or electrochemical detection. Fielden also considered the expanding field of postcolumn immobilized reagent-based detection. Along this line, Freeman, Daunert, and Bachas (C3) reviewed biochemical postAnalytical Chemlstry, Vol. 66, No. 12, June 15, 1994 *
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column reaction detection in liquid chromatography. The use of enzymes, binding proteins, and antibodies werediscussed in the context of improving both the selectivity and sensitivity in detection. Recent challenges in environmental analysis and monitoring for pollution prevention were described by Martin-Goldberg, Raymer, Voyksner, and Pellizzari (C4). Several analytical technologies were examined, including some liquid chromatographic instruments, that hold promise for the application in pollution prevention and control. In a related review by Chau (CS),chromatographictechniques that provide metal speciation were evaluated. Combination of liquid chromatography,which should separate with the metal-ligand structure intact, with element specific detection was found to be very attractive for metal speciation analysis in air, water, sediment, and fish samples. Two patents were reported on the subject of chromatographic detection. A multipoint detection method for electrophoresis and chromatography in capillaries was described by Hjerten and Srichaiyo (C6). A similar method was reported by Obst and Thietz (C7), in which signals from detectors arranged along the length of the column are used to generate a new set of time signals defined by the time required for a given analyte to travel from one detection site to the next. Both of these patents appear to be dealing with variations on the theme of whole-column detection. In the emerging area of D N A analysis, a few reports dealt with evaluating the quantitative accuracy and precision in the liquid chromatographic separation and detection of polymerase chain reaction (PCR) products. The amplification of D N A by the PCR allowed for accurate quantitation without requiring radioactivity labeling, as described by Gaus and co-workers (C8). In a complimentary study, Schmitt and co-workers (C9) describe how coamplification of a second genomic species serves as an internal standard in the PCRbased liquid chromatographic analysis of the primary genomic species, fibroblast growth factor /3, found in various cells and tissues. Another report by Asakawa and co-workers (ClO) described the accurate detection of heterozygous carriers of a deletion following PCR and liquid chromatographic separation. Imaging of the liquid chromatographic process by magnetic resonance imaging (MRI) was shown to provide information previously inaccessible by other investigative methods. Ilg and co-workers (C11) have shown that MRI provides realtime imaging of chromatographic processes, as well as diagnostic information concerning the physical state of the column. D. ABSORBANCE DETECTORS The primary focus of this review section is to report on the fundamental developments in absorbance detection such as new detector instrumentation developments and novel detection methods. Although recent literature contains many reports of innovative separation techniques that utilize absorbance detection, these references will not be cited in this section. A few review articles are referenced. There were a number of reviews of specific applications for absorbance detectors. Tran ( 0 1 ) provided a review of photothermal detectors for HPLC. An extensive review on the separation of polar lipid classes by Pchelkin and Veresh4R
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chagin ( 0 2 ) cited 179 references. Castledine and Fell (03) gave a review of various strategies for peak-purity assessment in L C using diode array detection. An excellent new laser-based double-beam absorbance detector was described by Rosenzweig and Yeung ( 0 4 ) based on electronic noise cancellation. The detector was linear through almost 4 orders of magnitude and had an absorption noise level of 2 X AU, which is lower by 1 order of magnitude than commercial absorption detectors. Djordjevic et al. (05) addressed different ways to increase the sensitivity of UV/visible absorbance detection in hightemperature open-tubular LC. A novel approach was taken in employing fiber-optical bundles with on-column detection yielding a significant increase in sensitivity with only a small decrease in efficiency. Castledine et al. (06) assessed the utility of pH-induced spectral shifts for enhanced peak-purity detection. They found that postcolumn methodologies for enhanced peak-purity detection were not realizable for impurity levels less than 2% (w t / wt) . A method was described by Lu et al. ( 0 7 ) for the determination of hydroxy acids which did not require any pretreatment or derivatization. The hydroxy acids are detected as their copper(I1) complex in an alkanesulfonate and acetate buffer containing copper ions following separation on a conventional reversed-phase column. The influence of pH, copper ion concentration, and buffer concentration provided a powerful means of controlling selectivity and sensitivity. Using a computerized photodiode array system, Jinno et al. ( 0 8 ) found that pattern recognition techniques provided a method of investigating structure/activity relationships as predictors of carcinogenicity for a series of large polycyclic aromatic hydrocarbons (PAHs). A data set was formed from a series of PAHs for which carcinogenic data was available and was used to predict the carcinogenicity of another set of PAHs. The results were consistent with the reported carcinogenicity of the second set. Cela, Lores, and Garcia (09)explored the applicability of a postcolumn photochemical reactor for polyphenolic compounds using absorbance detection. The authors discuss the optimization of variables affecting this experimental device such as reactor length, pH, and the nature of the modifiers in the mobile phase. A number of new hyphenated procedures have been presented recently. Lin (010) devised a general screening method for alkaloid drugs in foods, based on H P L C with UV/ visible absorbance detection a t three wavelengths followed by fluorescence and electrochemical detection in series. Relative response ratios from all the detectors provided a fingerprint of the drugs which could be used to predict the identity of an unknown component in a sample matrix. The fluorescence and electrochemical detectors allowed a detection limit which would not be obtainable with the absorbance detector alone. Bounoshita et al. ( 0 1 1 ) combined absorbance detection with polarimetric detection to provide enantiomeric compositional ratios from the peak ratios of the polarimetric and absorbance detectors for caraway and spearmint extracts. Lurie et al. ( 0 12 ) found that continuous on-line post-elution photoirradiation followed by either diode-array absorbance or thermospray mass spectrometric detection can greatly enhance
the specificity of analysis for certain analytes, with demonstration on a number of selected compounds. Some recent work done on absorbance detection for ion chromatography has been reported. Jackson and Bowser (D13) studied eluant systems suitable for use with simultaneous conductivity and absorbance detection. Octanesulfonate/ borate was reported to be the most versatile choice. An interesting method of absorbance detection of various cations was presented by Pastore et al. (DZ4).After chemical suppression of the eluant, measurement at 200 nm reveals the presence of hydroxide ion, which bears a stoichiometric relationship with the eluted Mn+ cations. Detection limits and sensitivities were similar to those obtained by the usual conductimetric methods. Hrdlicka et al. (D15)devised a detection scheme for rare earth elements separated on an ODS column based on a postcolumn reaction with xylenol orange and cetylpyridinium bromide. The sensitivity was usually better than 1 pg/mL and the results obtained were in good agreement with those obtained by ICP-AES. Li (D16)discusses factors that affect the signal-to-noise ratio in HPLC with absorbance detection, such as sample concentration, injection sample volume, detector lamp energy, wavelength, time constant, and mobile phase. Various methods for optimizing absorbance detection are discussed. Mathematical techniques in absorbance detection have been a major focus of research recently; however, only a few articles will be mentioned in this review. The chemometrics review provides a complete review of mathematical analysis in chromatography and other methods of chemical analysis. Castledine et al. ( 0 1 7 ) described a novel approach for the selection of absorbance ratios for the assessment of peak purity in LC, using a matrix derived from all the spectral data collected from a diode-array detector. The absorbance ratio matrix technique eliminates the need to select appropriate wavelength pairs, yet provides comparably high sensitivity to the presence of coeluting species as compared with the use of the wavelength pair selected on the basis of the conventional optimization criteria. Wang and Kowalski (D18)presented a method to standardize two-dimensional responses for a UV/ visible absorbance diodearray. The proposed method reduced the variation between two runs from 0.15-0.20 to 0.025-0.03 AU for experimental L C absorbance data. Yau et al. (D19) discussed the results of a newly developed method for characterizing chromatographic band broadening based on an exponentially modified Gaussian peak shape model. The method requires only the peak retention time, peak height, peak area, and peak centroid. The proposed method is less subject to baseline noise than previous methods and offers a reasonable compromise between accuracy, precision, and convenience.
E. CHEMILUMINESCENCE DETECTORS Chemiluminescence (CL) detection in LC has gained popularity due to the excellent sensitivity and selectivity of the technique. Detection limits in the pico- and femtomole range are commonly reported. In some cases, the detection limit in CL is superior to those for fluorescence. This section contains a discussion of reviews on the analytical technique, development of novel instrumentation, and fundamental studies of photolysis coupled with CL. Discussion of novel
reagents and of applications of C L is omitted because these topics will be covered in other reviews. The number of reviews that focus on CL indicates the extensive interest in the technique for chemical analysis. Stanley ( E l ) wrote a review with 15 references that surveys more than 90 commercially available luminometers, representing more than 60 companies, covering manual, automatic, and specialized operation of these instruments for use with HPLC, LC, GLC, and microliter plates. A review with 57 references was written by Hage ( E 2 ) that covers the basic principles of CL, covers its use for detection in HPLC, and describes and compares applications of and advantages of CL, respectively, over other techniques. Long-lived luminescence, including room-temperature phosphorescence, sensitized phosphorescence detection, quenched phosphorescence detection, and lanthanide luminescence in liquids is described in a review with 30 references written by Gooijer, Schreurs, and Velthorst ( E 3 ) . Worsfold ( E 4 wrote a review with 10 references that describes the basic principles of FIA and HPLC in combination with C L and bioluminescence detection. A review with 132 references was written by Rozhitskii ( E 5 ) that is dedicated to electrochemiluminescence (ECL) related analytical methods. Applications and basic principles for ECL with FIA and HPLC, heterogeneous ECL, direct and indirect ECL, and luminescence upon electrolysis are detailed. A review with 63 references that outlines pico- and femtomole detection limits for C L with LC used in pharmaceutical, biological, toxicological, environmental, or alimentary applications was written by Mahuzier et al. (E6). Direct and indirect potentiation of luminescence by the addition of modifiers or by transfer of energy from an excited molecule, respectively, is illustrated. Kwakman and De Jong (E7) wrote a review with 31 references that surveys the mechanism and applications of peroxyoxalate chemiluminescence (POO-CL), highlighting the sensitivity of the technique for HPLC. Several developments in instrumentation for CL were reported. Bryan and Capomacchia ( E 8 ) report the use of stop-flow oxalate ester CL to determine conditions for HPLC C L detection using normal-phase chromatography. A prototype unit from High-Tech Scientific, Ltd., and a Schoeffel 970 detector were used to survey retinoids. Hayakawa et al. (E9)describe a universal POO-CL detection system for mobile phases of differing pH. A dual-head short-stroke pump and two postcolumns are used. The first postcolumn contained 0.5 M imidazole/HN03 (pH 7.5) and MeCN in a 1:4 ratio, while the second postcolumn was MeCN containing TCPO/ H202. Femtomole sensitivity for perylene was reported using mobile phases from pH 2.0 to 8.0. A rotating flow device having three directional inlets, two with a 0.3 and one with a 0.5 mm i.d., was developed for HPLC and reported by Sugiura, Kanda, and Imai (ElO). The acidic column eluate, chemiluminogenic reagents, and imidazole solution are mixed and passed through a common outlet. Detection limits of 10 amol for dipyridamole and subfemtomole for various dansylated amino acids were reported. Conboy and Hotchkiss ( E l l ) report a photolytic interface apparatus and its use in series between a HPLC and C L detector. HPLC effluent is introduced into a glass coil with a purge stream of He and irradiated with UV light. Cold traps are used to separate the analyte from solvent, which is subsequently carried to the Analytcal Chemistty, Voi. 66,No. 12, June 15, 1994
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detector by the He. Instrument design and applications are presented. Fujinari and Courthaudon (E12)report a detector for the routine and continuous detection of a HPLC C L nitrogen detection system. Brune and Bobbitt ( E l 3) report a postcolumn C L technique for the detection of underivatized amino acids. The reaction chemistry and detection limits of the system are characterized and reported. Velthorst et al. ( E 1 4 report a scheme for C L detection in HPLC based on quenching of the analyte in the triplet state by a triplet ground-state molecule, inducing promotion to the singlet excited state. Subsequent reaction allows for detection by thermally induced CL. The use of a single reagent pump postcolumn detector was optimized for the investigation of the detection of nitrosamines in a report by Fu, Xu, and Wang (E15).Sensitivity of the method was found to be 120 times that of fluorescence, with detection limits on the order of pico- to subpicograms of analyte. Background intensity in POO-CL detection was reduced while sufficient analyte intensity was maintained using bis(2,4,6-trichlorophenyl) oxalate in a report by Hanaoka and Tanaka ( E 1 6 ) . Detection limits of 2-4 fmol were reported for dansylated amino acids.
F. ELECTROCHEMICAL DETECTORS This section is arranged as follows: Reviews and Comparative Studies, New Detectors, New Electrodes, and Novel Electrochemical Applications. Reviews and Comparative Studies. An extensive review of electrochemical detection for liquid chromatography was prepared by Wang ( F 1 ) . Principles, mobile-phase requirements, electrodes, cell design, detection modes (amperometric, voltammetric, multiple electrode, tensammetric, improved detection via derivatization, conductometric, and potentiometric), and applications were discussed. A review by Stulik ( F 2 ) of electrochemical detection for flow analysis and liquid chromatography focused on recent developments in potentiometric and voltammetric detection. Pulsed electrochemical detection for the detection of polar aliphatic compounds was reviewed by LaCourse ( F 3 ) and Johnson ( F 4 ) . A review of column liquid chromatography in combination with immobilized enzymes and electrochemical detection was prepared by Marko-Varga ( F 5 ) . I n addition to a discussion of the application to industrial processes, there is an outline given of important factors to consider in system optimization. Instrumentation for L C with electrochemical detection for long-term automated monitoring of metal ions in industrial effluents was the subject of a review by Bond ( F 6 ) . Kilts ( F 7 ) prepared a review on the impact of HPLC with electrochemical detection on the field of neuroendocrinology. Recent advances in electrochemical detection in liquid chromatography were discussed in a review by Wang ( F 8 ) . Subjects covered include detection design, multiple electrodes in thin-layer flow cells, ion transfer across a water/solidified nitrobenzene interface in a flow system, and chemically modified electrodes. In a comparative study by Maruyama ( F 9 ) , HPLC with amperometric detection was used for the determination of trace amounts of 3,4-dichloroaniline and found to be preferable when compared to G C and HPLC/UV methods. Electrochemical and UV detection were compared for the microcolumn HPLC determination of trace amounts of phenylurea 6R
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herbicides in water by Boussenadji and co-workers (FIO). Electrochemical detection was found to offer the advantage of higher selectivity when heavily contaminated water was used by detecting only the electrochemically active components. New Detectors. The use of multiple electrodes and arrays for electrochemical detection has continued to be an area of new developments. Svendsen ( F 1 1 ) described the concept of three-dimensional chromatography by use of multielectrode detectors with gradient chromatography to increase both the range of compounds in samples that can be identified and the confidence with which they can be matched to known standards. Aoki and co-workers (5’1 2) described a 16-channel microelectrode array for FIA and HPLC. The 16-channel detection was performed by collecting current responses at 16 microband electrodes held a t potentials that differed stepwise by means of a multipotentiostat to show three-dimensional results (time, current, and potential). An 80-channeldetection scheme was also carried out by applying a five-step potential staircaseof 10-mV step height on the 15 individual electrodes. A coulometric detector containing four porous carbon electrodes was developed by Takai andco-workers(F13)toanalyze catecholamines, serotonin, and related amines in body fluids. Potentials were maintained a t 300, 400, 500, and 600 mV vs Ag/AgCl. Simultaneous on-line UV absorbance and electrochemical detection were used for micellar electrokinetic capillary chromatography of pungent compounds by McNair and co-workers ( F 1 4 ) . The development of a reticulated vitreous carbon spectroelectrochemical detector for FIA and L C was described by Sorrels and Dewald (F15).A mixture of phenol, chlorophenols, and nitrophenols was used to investigate simultaneous electrochemical and optical response in LC. A flow-through semiconductor-based titanium dioxide photoelectrochemical detector for FIA and L C was developed by Brown and co-workers (F16). An automated procedure for optimization of all potential and time parameters in pulsed amperometric detection waveforms on the basis of pulsed voltammetry at a rotated disk electrode was described by LaCourse and Johnson (F17). A new electrochemical detector with carbon fibers as the working electrode placed perpendicularly to the flow direction was described by Mattusch and co-workers ( F 1 8 ) , and the performance characterized with phenolic compounds. White and co-workers ( F 1 9 ) described the use of a carbon microvoltammetric working electrode in a rapid-scan HPLC detector. The optimization of the design of a thin-layer cell with a single electrode for electrochemical detection was described by Righezza and Siouffi (F20). The behavior of a potentiometric detector was studied in an LC system for the detection of organic acids by De Backer et al. ( F 2 1 ) . Ion-selective PVC-based liquid membranes with two types of carriers were used, and these flow-through detectors were compared with amperometric wall-jet detectors and UV detectors. In order to improve the sensitivity of voltammetric detection in HPLC, Long and Weber ( F 2 2 ) investigated the use of large-amplitude sine wave potential perturbations and signal processing techniques such as digital bandpass filtering. A new amperometric cell with a small platinum wire working electrode, a submicroliter geometric volume, and a solid polymer electrolyte (Nafion) was constructed and tested by Loub and co-workers (F23). The cell was found to permit
sensitive and reliable detection even in mobile phases of negligible electrical conductivity. A new electrochemical detector was developed by Mattusch and co-workers (F24) that has a special arrangement of the working electrodes which make possible simultaneously serial and parallel operation methods in dual-electrode detectors. An electrochemical sensor based on the incorporation of dodecyl sulfate into polypyrrole by electropolymerization of pyrrole in the presence of surfactant was described by Carabias-Martinez and coworkers (F25). New Electrodes. Interdigited array microelectrodes in which both the band width and gap are 2 pm were fabricated and applied in electrochemical detectors for FIA and HPLC, as reported by Takahashi and co-workers (F26, F27). The use of conductive carbon cement as the electrode matrix for cobalt phthalocyanine-modified electrodes for the determination of cysteine in urine samples was described by Huang and Kok (F28). A cobalt-based glassy carbon chemically modified electrode was prepared by Cataldi-Tommaso and co-workers (F29) and used for the determination of carbohydrates and related polyhydroxy compounds after anion-exchange chromatographic separation. A copper-based chemically modified electrode was constructed and characterized for flow-through amperometric detection of catechol, resorcinol, and hydroquinone by Zhou and Wang (F30). The same workers (F3I) constructed a novel Prussian blue chemically modified electrode and characterized it for LC electrochemical detection of catecholamines. Zhou and Wang (F32) also reported a glassy carbon electrode coated with an electrodeposited film of mixed-valence cobalt oxide/cyanocobaltate that was used for the determination of hydrazine compounds. A glassy carbon/PEEK composite electrode was described by Fung and Saunders (F33). A glassy carbon linear array electrode was the subject of a US.patent for Magee and Osteryoung (F34). Nickel/copper and nickel/chromium/iron alloy electrodes were used for amperometric detection of carbohydrates after anion-exchange LC separation by Marioli and Kuwana (F35). A carbon fiber-based flow electrode in a microelectrochemical cell was used for the determination of salbutamol in human plasma after HPLC separation, as reported by Sagar and co-workers (F36). It was found to have some advantages over conventional electrochemical detectors using glassy carbon electrodes. Novel Electrochemical Applications. Pulsed amperometric detection (PAD) of amino acids separated by anion-exchange chromatography was reported by Martens and Frankenberger (F37). PAD was more sensitive than ninhydrin derivatization with UV absorbance detection. The simultaneous measurement of monamines, metabolites, and amino acids in brain tissue and microdialysis perfusates was developed by Gamache and co-workers (F38),using HPLC with a coulometric array of graphite flow-through electrodes. Electrochemical detection of peptides and proteins was achieved with a postcolumn photochemical derivatization step, as reported by Krull and Dou (F39,F40),leading to the formation of electrochemically oxidizable photoproducts. Amperometric and fast-scan-rate cyclic voltammetry at a 10-pm-diameter platinum microelectrode were utilized by Soucaze-Guillous and co-workers (F4I) for the detection and in situ identification of fullerenes which were separated by gel permeation HPLC. A new HPLC
method for the separation of tetramethyllead and tetraethyllead was developed, and amperometric and PAD were investigated for EC detection of these alkyllead species by Robecke and Cammann (F42).Rose and Shearer (F43)used HPLC with electrochemical detection to determine tranquilizers and carazolol residues in animal tissue It was found that EC detection gave up to 10-fold improvement in limits of detection in comparison to existing UV absorbance and fluorescence detection for pig kidney analysis. An amperometric FIA system with immobilized enzyme reactors or enzyme sensors was used as a postcolumn detector for HPLC by Yao (F44).Bergens (F45)described a scrubber column which was used to reduce and eliminate the dissolved oxygen in an acidic mobile phase in LC. The scrubber column is made by packing a column with zinc amalgam particles and is mounted between the pump and the injection device. It enables sensitive amperometric detection at potentials down to -0.65 V vs Ag/AgCl. A novel in situ electrochemical complex formation method for selected metal ions was reported by Wang and Liu (F46). The system is based upon the use of polymeric material as a conducting agent into which the complexing agent pyrrolidine dithiocarbamate ligand is incorporated. Berglund and Dasgupta (F47) presented a simultaneous cation-anion-exchange scheme in which effluent acids from a suppressed anion chromatographic system proceed through the annular channel of a dual-membrane converter. A novel approach to simultaneously practicing both suppressed and nonsuppressed ion chromatography using sequential conductivity detectors was proposed by Berglund, Dasgupta, Lopez, and Nara (F48). These dual-channel data provide additional information as the investigator seeks to perform qualitative and quantitative analysis.
G. FLUORESCENCE DETECTORS Fluorescence detection is commonly used in liquid chromatography because it offers high sensitivity and selectivity. Many interesting new applications have been reported in the literature. In the interest of brevity, this review article will be limited to listing the reviews, instrumentation developments, new techniques, and tagging reagents. Edkins and Shelly ( G I ) wrote a review with 82 references discussing figures of merit for laser radiation detection in microdetection schemes using fluorescence, absorbance, optical activity, and scattering detectors. Rahavendran and Karnes (G2) and Mank et al. (G3) reviewed developments in fluorescence analysis using diode lasers. Coquet et al. (G4) evaluated the performance of postcolumn fluorescence and evaporative light-scattering detection for the selective analysis of saccharides with LC. The authors compared factors such as reproducibility, detection limit, and linearity of calibration and concluded that postcolumn derivatization is superior from the standpoint of sensitivity, despite requirement of the derivatization reaction step. Sweedler et al. (G5) described the application of a CCD in a timed integration mode for use as a fluorescence detector. The CCD is synchronized so that charge information in every row of the CCD is shifted toward one end of the device after each exposure, and the charge/signal information quantified at the last row element. Applying the CCD in this timedelayed mode offers an effective increase in sampling volume Analytical Chemistry. Vol. 66, No. 12, June 15, 1994
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of the flow cell without introducing band broadening. The technique is applicable to both capillary liquid chromatography and CZE. There have been some recent reports of new uses of diode lasers for fluorescence detection. Mank et al. (G6) reported a new cyanine dye for derivatizing thiols. The new thiol label can be used with a visible diode laser and provided a detection limit of 8 X 10-l2 M for the tested thiol. Lehotay et al. (G7) evaluated a diode laser-based indirect fluorometric detection scheme for n-alkyl alcohols. A near-IR dye, IR 125, was added to the mobile phase and analytical measurements of n-alkyl alcohols were made by measuring the induced change in the I R 125 fluorescence signal a t the alcohols’ retention times. Limits of detection were on the order of lo-* mol injected. Imasaka et al. (G8) utilized a blue semiconductor laser for laser fluorometric detection of two polycyclic aromatic compounds after separation by cyclodextrin-modified micellar electrokinetic chromatography. The blue laser radiation was obtained from the second-harmonic emission of a near-IR semiconductor laser and produced a native fluorescence in the polycyclic aromatic compounds which allowed a detection limit on the order of 1 X M. Abbas and Shelly (G9) described a micro-LC flow cell featuring axial illumination in a fused silica capillary and mobile-phase elimination by nebulization for laser-induced fluorescence and refractive index detection. The optical wave guide properties of fused silica capillaries provide a greater illuminated sample volume by axial illumination than by cross capillary illumination. Bostick et al. (GZO) developed a highly sensitive laser-induced fluorescence detector for analysis of biogenic amines using a He/Cd laser. The amines are derivatized by naphthalenedicarboxaldehyde in the presence of cyanide ion to produce a cyanobenzV]isoindole which absorbs radiation a t the output wavelength of the He/Cd laser (441.6 nm). Optimization of the detection system yielded a detection limit of 2 X 10-l2 M. Williams and Barnett (GZZ) described the use of 8-quinolinol-5-sulfonic acid as a nonselective postcolumn reagent for fluorometric detection of trace metals in ion chromatography. After separation, the analyte ions react with Mg-EDTA to displace free magnesium ions which in turn react with the tagging reagent to provide a fluorescent product. Ramos and Mike (G12) reported the successful application of an electrochemical reactor for postcolumn fluorescence detection of catecholamines. Since base-catalyzed tautomerization of the oxidation products of these compounds produces a highly fluorescent species, no derivatizing agents are required. Primary and secondary alcohols can be tagged with a fluorescence derivative studied by Yoshida et al. (G13). The detection limit for 1-propanol was 70 fmol for a 10-pLinjection volume. Fluorescent chiral derivatizing agents for carboxylic acids have been reported by Toyooka et al. (G14) and by Kondo et al. (G15) which enable the separation of enantiomeric carboxylic acids while providing a highly fluorescent reaction product. Some interesting and novel new separations utilizing fluorescence detection have been reported lately. Sharma and Freund (GZ6) developed a precolumn derivatization method for HPLC analysis of DNA damage using fluorescence detection. In their procedure, the modified nucleotide is 8R
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enriched from the normal nucleotide and labeled with dansyl chloride. By combining microbore H P L C with laser-induced fluorescence detection, this system is capable of a subfemtomole detection limit for real-time analysis of dansylated nucleotide. Iwaki et al. (G17) described the use of disodium EDTA and calcium chloride as fluorescence increasing reagents for the determination of tetracycline antibiotics. The largest fluorescence intensity for tetracycline was produced in a mobile phase when the concentrations of EDTA and CaC1, were 25 and 35 mM, respectively, and the pH was 6.5. The detection limits of the method ranged from 49 to 190 pg for three different tetracycline compounds. Irth et al. (GZ8) utilized a postcolumn on-line immunochemical detection system for a very selective and sensitive method for determination of digoxin and digoxigenin. Fluorescein-labeled antibodies are used to target the chosen analytes and the fluorescence detection system provided detection limits of 200 and 50 fmol, respectively, for digoxin and digoxigenin. Schneede and Ueland (GZ9) described a novel new method for the analysis of methylmalonic acid. Derivatization with 1-pyrenyldiazomethane produced a 1-pyrenylmethyl monoester for methylmalonic acid, leaving a free carboxylic acid group. Other short-chain dicarboxylic acids produced the diester so the monoester was easily separated from the other derivatives by adjusting the p H of the mobile phase. These data could form the basis for the construction of an automated methylmalonic acid assay. H. INDIRECT DETECTION When the desired analytes possess low sensitivity to the detection mode employed (absorbance, fluorescence, conductivity, etc.), the 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 phase according to definite mechanisms such as conservation of charge, ion pairing of volume displacement, or whenever the injected analytes compete with or perturb the equilibrium of the visualizing agent between the mobile and stationary phases. Glavina and Cantwell ( H I ) investigated the origin of indirect detection of butanol when adding an anionicvisualizing agent, naphthalene-2-sulfonate (NS), to the mobile phase in reversed-phase LC. The authors reported that the indirect signal for butanol was attributable to displacement of NS in the O D S stationary phase by butanol. They also found that butanol, in the concentration range 0-0.04 mol/L, does not significantly alter either the solvent strength of the mobile phase or the sorbent strength of the bonded phase for NS. A differential indirect detection scheme was described by Kawazumi et al. ( H 2 ) and applied to detection of aliphatic alcohols after reversed-phase micro-LC. The differential measurement with single capillary cell and double beams improved dynamic reserve and detectability. The deep red dye employed as a visualizing agent allowed the use of a visible semiconductor laser. The mass detection limit was in the sub microgam range. Kaljurand et al. ( H 3 )used correlation ion chromatography to improve the signal-to-noise ratio in the indirect absorbance
detection of ions. A binary pseudorandom injection of a sample containing low concentrations of common anions was found to enhance the S/N ratio in good agreement with theoretical predictions. Tunuli ( H 4 ) proposed a new indirect detection technique based on perturbation of oxygen reduction at a gold or gold chloride electrode. The proposed scheme exploits the influence of the analyte on the reduction current of an intrinsic mobilephase additive, oxygen, at the detector electrode, and utilizes the resulting changes in background current as an analytical signal. Groh and Baechmann (H.5) reported the use of potassium hexacyanoferrate(I1) and -(III) as eluants for the indirect absorbance detection of anions. Five anions were separated in a 6-min isocratic run with detection limits in the subpicogram range. Michigami and Yamamoto (H6) investigated the behavior of the system peak in ion chromatography with indirect absorbance detection and trimellitate as the eluant. The intensity of the system peak depended upon the pH of the sample injected and on the injected anion concentration. Zou et al. ( H 7 )described the benefits of using naphthalene- 1,5-disulfonate as the eluant in reversed-phase ion-interaction chromatography of inorganic anions using indirect absorbance detection. Among the many advantages of this eluant are UV absorption at fairly long (300 nm) wavelengths, strong UV absorption by the eluant, ready solubility in methanol/water mixtures and relatively low cost. Yuan and Pietrzyk (H8)used ruthenium(I1) 1,lO-phenanthroline salts as mobile-phase additives for the separation and indirect detection of free amino acids. Detection limits for the separation and detection of free amino acids using isocratic elution were about 0.1-0.25 nmol. Maki et al. (H9) accomplished the separation and detection of aliphatic anionic surfactants using a weak anion-exchange column with indirect photometric and indirect conductivity detection. In the method described, selective separation of C ~ - C alkanesulfonates I~ and alkyl sulfates was achieved in less than 9 min with a linear response from greater than 500 ppm to the sub-ppm level.
I.INFRARED DETECTORS A general discussion of the advantages and limitations of various approaches to coupling LC with Fourier transform infrared (FT-IR) detection is given by Fujimoto and Jinno (11).Kalasinsky and Kalasinsky (12)also published a general review of HPLC/FT-IR. Patonay and Czuppon (13)reviewed the use of near-IR-absorbing chromophores as labels. The wide application of the coupling of semiconductor laser diodes with covalent labeling is discussed. Meyer, Salzer, and Raddatz (14)compare two types of interfaces for HPLC/ FT-IR. The limit at which identification was possible for the on-line flow cell was found to be at least 1 order of magnitude higher than the off-line method, in which thediffuse reflectance of the solute in a powdered cup is measured after evaporation of the solvent. Near-IR luminescence spectrometry was reviewed by Akiyama (15). A thermospray interface has been developed by Robertson and co-workers (16) that deposits effluent on a moving metal substrate, where it is desolvated. The solutes are transferred into a diffuse reflectance accessory of an FT-IR spectrometer. Although the efficiency of deposition has a 13.5% RSD, it is an improvement over performance without thermospray
temperature control. DiNunzio (17) applied solid-phase extraction (SPE) to HPLC/FT-IR for problems of pharmaceutical interest. The advantages of the SPE interface, and its use in on-column and on-extractor preconcentration to increase sensitivity, described. Griffiths and Lange (18)describe an interface in which the effluent is converted to an aerosol using a concentric flow nebulizer. In an evacuated housing, the eluates are deposited on a moving zinc selenide window. After a chromatographic run, the window is translated so that the starting point of the deposited track is a t the focus of the beam condenser. IR interferograms are measured a t 0.2% intervals with the same window speed. The same authors (19)used the instrument to measure spectra from both volatile and nonvolatile buffers in mobile phases consisting of 63-100% water. For volatile buffers, little or no spectral subtraction was needed at low buffer concentrations, while the absorption bands of nonvolatile buffers were seldom completely removed. Minimum quantities for which identification was possible were in the low nanogram range. A new sample introduction system has been developed by Lam et al. (110,112) for the analysis of continuously flowing liquid streams by flame I R emission (FIRE) spectrometry. Effluent is treated with peroxydisulfate in the presence of silver ion to convert analytes to C02. A purge cell strips dissolved C 0 2 from solution into a hydrogen gas stream that serves as fuel for a hydrogen/air flame. The COz emission band is monitored.
J. LCIMS Combination of the separating power of LC and the analyzing power of M S (LC/MS) has led to the development of a useful tool for analytical chemistry. Due to its high selectivity and sensitivity, L C / M S is finding increasing use in the analysis of a wide range of compounds in complex mixtures. Many L C / M S interfaces and ionization methods were reported, including those for fast-atom bombardment (FAB) and chemical ionization, thermospray, particle beam, ion spray, electrospray, atmospheric pressure ionization, and inductively coupled plasma (ICP) and plasma spray. Reviews of the Field. Several comprehensive reviews that focus on differing aspects of L C / M S interfaces and ionization methods were reported this period. Jinno (JZ)wrote a review for L C / M S and packed and capillary column G C / M S covering thermospray, plasmaspray, and moving belt interfaces. A review with 161 references written by Tomer (J2) describes various L C / M S interface designs and analytical applications. Van der Greef and Niessen (J3)present a review with 89 references that discusses the tunability of the detection selectivity for L C / M S and electrophoresis/MS. The use of L C / M S in environmental organic analysis is reported in a review with 145 references by Barcelo (J4) that covers electron impact and positiveand negative chemical ionization. Column switching, ion trap technology, electrospray, and continuousflow dialysis are discussed in a review with 29 references by Niessen, Tjaden, and Van der Greef ( J S ) . Plasma desorption MS, isotope dilution MS, ICP-MS, and thermal ionization are reviewed in a supplemental report with 56 references by Budzikiewicz (J6) while atmospheric pressure ionization is discussed in a review with 8 references by Kaudewitz (J7). Analytical Chemism, Voi. 66,No. 12, June 15, 1994
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Arpino ( J 8 ) wrote a review with 110 references about various L C / M S coupling techniques for the study of biological molecules. Fast Atom Bombardment (FAB). Ikai et al. ( J 9 )evaluated the applicability of a flow splitter and a pneumatic splitter to frit-FAB L C / M S to illustrate the influence of viscosity on the flow split. The split from pneumatic splitters was found to be dependent upon mobile-phase viscosity, and the advantages of a flow splitter are highlighted. An interface for a normal-phase fused silica capillary H P L C system to a continuous-flow FAB detector is described by Lawrence (JI 0). The experimental parameters that differ for aqueous solvent systems are described. Many FAB techniques, especially negative ion ionization, are discussed in a review by Mellon (JI I ) . Potential improvements to current methodologies are presented. Lecoq, Di Biase, and Montanarella (512) report means to couple micellar capillary electrophoresis to FABM S with a review of parameters such as the reproducibility of migration times and injections and the maximum mass loading. Positive and negative chemical ionization are combined for superior analyte identification in a report by Kuksis, Marai, and Myher (J13). Quantitation of triacylglycerides in mixtures such as butterfat and fish oil is presented. Carrier, Gagne, and Bertrand ( J I 4 ) examine the precolumn addition of viscous matrices, such as triglycerol, on the chromatographic performance of FAB LC/MS, showing that chromatographic indicators are only slightly affected for concentrations of up to 3% triglycerol in the mobile phase. The complete exchange of protons with deuterons in FAB L C / M S is reported by McLean et al. (J15) by using a deuterated mobile phase with microbore HPLC. Thermospray. Arpino (J16) wrote a review with 295 references covering thermospray L C / M S and its applications for organic analysis. The stability of the ion beam as a function of vaporizer temperature is discussed in a report by East et al. ( J 1 7 ) . Repositioning of the thermocouple amplifier and replacement of the time-proportional part of the circuit with a phase angle controller led to improved temperature and, therefore, ion current, stability. Hau, Nigge, and Linscheid (J18)present a new ion source for thermospray based ontwo sets of electrostatic lenses used to focus the divergent ion beam that emanates from the external cone into the ion source region. Implementation of the new design is illustrated with some sample analyses. Anion-exchange chromatography and thermospray M S are interfaced via an anion micromembrane suppressor and booster pump in a report by van der Greef et al. ( J I 9 ) . Application of the analyzer scheme is suggested for the examination of oligosaccharides. Gaseous ammonia is added to a thermospray ion source, followed by filament-on ionization, to generate chemical ionization reagents in a report by van Leuken and Kwakkenbos (520). Advantages for use with normal-phase L C / M S aredescribed. Vreeken et al. ( J 2 I ) present the use of benzenesulfonic acid as a trapping column material in a phase switching system for thermospray LC/ MS. Sorption and desorption involving the trapping column is studied. A modified discharge mode thermospray device, comprised of a coaxial capillary structure, is reported for use with L C by Kanohta (J22). The outer stainless steel shell holds a fused silica capillary that is resistively heated to generate the misty eluate stream that is passed on for analysis. 10R
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Hsu ( J 2 3 ) presents the use of water cluster ions in either filament-on or discharge ionization modes for easy calibration of thermospray LC/MS. Cluster ions of sizes from 1 to 44 water molecules are reported. Particle Beam (PB). Bier, Winkler, and Herron ( J 2 4 ) present a description of a particle beam interface to a LC/ M S system. Details involving the pneumatic nebulizer, desolvation chamber, and three-stage separator region are discussed. A particle beam L C / M S system with improved signal linearity and enhanced sensitivity is reported by Apffel, Nordman, and Martich (J25). A closed-coupled momentum separator with integral removable source volume is described and used to minimize the number of particles lost in the separator. Behymer et al. ( J 2 6 )examine the feasibility of PB L C / M S as a general-purpose, broad-spectrum analytical tool for environmental analysis of nonvolatile organic compounds. Three different PB interfaces were examined. Comparison between two different PB L C / M S systems, and the effect of those differences on ion abundance-enhancing carriers, is presented by Ho et al. ( J 2 7 ) . A membrane suppressor for continuous desalting was successfully interfaced to a PB ion chromatography/MS system in a report by Hsu (J28). Sensitivity to six aromatic sulfonic acids on the order of the submicrogram level was reported. Cappiello and Bruner (J29) present a laboratory-made aerosol generator that can be interfaced to a Hewlett-Packard PB L C / M S system. Improved signal response and sensitivity were observed as the result of the aerosol generated by minimal solvent input (1-5 pL/min). The feasibility of use of a particle beam interface for quantification by isotope dilution L C / M S was investigated by Doerge, Burger, and Bajic (J30). Benefits in terms of signal enhancement and data processing simplicity were observed. The value of PB L C / M S for the examination of thermally sensitive compounds was reported by Chipman and Cruickshank (J31). Thermal transacylation reactions were observed for N-acyl derivatives of biotinol, and PB L C / M S is shown as a plausible alternative to probe M S for thermally labile species. Kleintop, Eades, and Yost ( J 3 2 ) examined several operational modes of a quadrupole ion trap M S (QITMS) for PB L C / M S analyses. The PB interface was coupled to the QITMS without an external ion source, and lower limits of detection were recorded for isocratic PB LC/ QITMS than for PB L C / M S for a series of pesticides. Ion Spray. A high-flow (up to 2 mL/min) ion spray interface for L C / M S is reported by Hopfgartner et al. (533). The system can be implemented without use of established postcolumn splitting of the flow and is amenable for gradient LC. Anion micromembrane suppression is used to couple high-performance anion-exchange chromatography with ion spray M S in a report by Conboy and Henion ( J 3 4 ) . Low nanomole detection of monosaccharides was observed. Da Col et al. (J35) report low picomole detection limits for complexes between nucleosides and cis-dichlorodiamineplatinum(I1) using a combination of reversed-phase H P L C and ion spray MS. A method compatible with pulsed amperometric detection was optimized for ion spray L C / M S for the analysis of aminoglycoside residues in bovine tissues was presented by McLaughlin and Henion (J36). Detection limits in the low nanogram range are reported.
Electrospray. Jaquinod and Van Dorsselaer (537)present a review with 23 references which describes basic electrospray ionization principles. A mechanism for electrospray ion production is discussed in a review by Juhasz et al. (J38). Nanoscale capillary LC and C Z E have been combined with quadrupole M S via an electrospray ionization interface. Detection limits in the low picomole range are reported by Perkins, Parker, and Tomer (539)for various sulfonamides. The effect of skimmer voltage on analyte dissociation is also discussed. Lee and Henion (540)present a thermally assisted electrospray interface that combines both thermo- and electrospray techniques. Labile compounds that undergo thermal composition by traditional thermospray show no decomposition with thermally assisted electrospray. Atmospheric Pressure Ionization (API). Allen and Shushan (J41)present a review with 32 references that discussed the technique and applications of API. Heated nebulizer and ion spray L C / M S inlets with positive and negative modes are compared by Thomson, Ngo, and Shushan (J42)in a discussion of API sources. Modifications to a commercially available benchtop G C / M S for use with API are presented by Duffin, Wachs, and Henion (J43). A complete description of the modifications and implementation of the API interface is presented. ICP-MSand Plasma Spray. ICP-MS analysis is becoming increasingly popular due to excellent selectivity and sensitivity. A review with 100 references is presented by Heitkemper and Caruso (J44) that discusses chromatographic sample introduction for plasma source MS. Emphasis on application to real samples is placed by Hill, Bloxham, and Worsfold (545) in a review with 127 references on ICP-MS systems. In a review with 40 references Vela, Olson, and Caruso (J46) discuss elemental speciation methods for LC, GC, and S F C coupled to ICP-MS and microwave-induced plasma (MIP) MS. Similarly, Olson, Heitkemper, and Caruso (547)present a review with 71 references on the topic of GC and LC interfaced to ICP-MS and MIP-MS. Instrumentation concerns, interfacing problems, and overall performance of the systems are discussed. Multielement and multiisotope detections were performed with ICP LC/MS using time-resolved analysis in a report by Owen et al. (J48). Rare earth elements were examined using ICP L C / M S in a report by Braverman (549). Detection limits in the sub nanogram per milliliter range with a 4 order of magnitude linear dynamic range are observed. A new version of the direct injection nebulizer for use with ICP L C / M S is presented by Shum, Neddersen, and Houk (J.50). All the sample is injected and a dead volume of less than 1 NL is reported, with a substantial increase in absolute detection limits and chromatographic resolution as compared to conventional nebulizers. Beckett (J51)presents a new technique, FFF-ICP-MS, for the analysis of complex particle or macromolecule mixtures. Miscellaneous Topics of Interest. Krost (J52) presents a study of a moving-belt LC/MS interface for use in the analysis of a wide variety of chemical species. A detection limit of 10 ng is reported for some of these species. Perreault et al. (353) examine the applicability of a moving-belt interface for LC/ MS in the analysis of polycyclic aromatic compounds, with good preservation of the chromatographic integrity. A refrigerated trap system is described by Snodgrass, Hayward,
and Thomson (J54)for mobile-phase recovery in LC/MS. Instrumentation lifetime can be increased by this method. Steiner et al. (J55)presents matrix-assisted laser desorption M S as a novel method for the analysis of large molecules. Application for synthesized peptide analysis is discussed. A multifunction Curie-point direct injection probe was developed and reported by Oguri et al. (556). Probe application and implementation is presented. Hsu and Qian (J57)report the use of CS2'+ formed under low-energy conditions for as an ionization source. Advantages of CS2 charge exchange for hydrocarbons with ionization potentials less than 9.5 eV as compared to low-voltage E1 ionization are presented.
K. OPTICAL ACTIVITY DETECTORS Circular dichroism (CD) measures the difference in absorbance of left and right circularly polarized light, while polarimetry relies on the difference in refractive index (RI) of the two components to rotate the plane of polarized light. Salvadori, Bertucci, and Rosini (KI)reviewed various methods to get stereochemical information from the CD signal. Also, they evaluated the use of the dissymmetry factor to evaluate the purity of chiral eluates. Mannschreck (K2) qualitatively and quantitatively reviewed single-wavelength polarimetric detection and explained why polarimetry is preferred for monochromatic use and why CD is better for polychromatic requirements. The limitations of chirooptic devices as stand-alone detectors are discussed by Zukowski et al. ( K 3 ) ,who showed the advantages of a UV/visible absorbance and CD detector in series for enantiomeric ratio determination without requiring chiral chromatographic resolution. Goodall, Robinson, and Wu (K4)used a combination polarimeter/near-IR absorbance detector to determine enantiomeric purity at the 1% precision level without chiral resolution. Polarimetry was used by Brooks et al. (K5)to measure small enantiomeric excesses in a study of free-radical oxidation. Zelenka, Leiminer, and Mannschreck (K6)utilized the entire spectrum of a tungsten halogen lamp to reduce noise in a newly developed polarimetric detector for HPLC. Nonstop acquisition of CD spectra during LC has been achieved by Brand1et al. (K7)using a new typeof spectrometer, built in-house. This device, which alsocollects UV absorbance data, can be used to identify and check the purity of enantiomers. All compounds can be made to appear optically active in a longitudinal magnetic field. Kawazumi et al. (K8)worked on an on-line detector for HPLC based on this property, called magnetooptical rotation (MOR). Since the detector is very sensitive to fluctuations in temperature and RI, a stable laser as well as a flow cell with a central inlet is necessary. Linearity of response has been improved to more than 2 orders of magnitude with a detection limit in the microgram range. L. REFRACTIVE INDEX DETECTORS Refractive index detection is widespread in LC due to the *universal" nature of the detector and is gaining popularity for use in process LC. Kolbert ( L I ) reports the design of a critical angle R I detector for use in production LC that can be used in systems with flow rates from 100 mL/min to 25 L/min and higher as required, and with pressures up to 4000 Analytical Chemistry. Vol. 66, No. 12, June 15, 1994
tlR
psi. The system includes a flow cell with a sensing chamber volume selected to provide maximum detector sensitivity and minimum pressure drop a t themaximum flow rate for accurate critical angle refractive index detection. Although valued as a “universal” detector, traditional RI is plagued by baseline drift and increases in baseline noise when used in conjunction with mobile-phase and thermal gradient LC techniques. Much of the recent work has focused upon minimizing these limitations. Mharte and Krull ( L 2 ) report the use of RI, UV, and low-angle light scattering (LALLS) in series for the on-line detection of the differential refractive index increment of the analyte. The use of two isorefractive buffers helped generate stable baseline conditions for the R1 and LALLS detector. This on-linedetection method was used to determine the molecular weight of proteins and required only 3-4 mg of sample, as compared to the 200 mg used in off-line techniques. Lima and Synovec ( L 3 ) report a further characterization of the refractive index gradient (RIG) detector that allows for the uncoupling of the effects of hydrodynamic convection and analyte translational diffusion upon the observed concentration gradient. Characterization of RIG detection behavior with high-temperature and thermal gradient LC demonstrated a stable and predictable baseline and a minimal increase in baseline noise. The dependence of RIG detection upon analyte translational diffusion was exploited by Murugaiah and Synovec ( L 4 ) . A typical RIG signal is a derivative-shaped peak comprised of a positive and negative going “half-peak”. A correlation between the asymmetry in the heights and maximum position of these “half-peaks” and the molecular weight of a homologous polymer series was reported, suggesting that RIG detection can be used as a molecular weight analyzer. Factors such as connecting tube length and collimated probe beam position are discussed in relation to the tunability of the detector to specific molecular weight ranges.
M. MISCELLANEOUS DETECTORS Atomic Absorbance Spectrometry (AAS). Klaentschi ( M I )compared atomic spectrometric methods including AAS, inductively coupled plasma atomic emission spectrometry (ICP-AES), ICP mass spectrometry, and X-ray fluorescence as detectors for ion chromatography. The recent applications of chelating, ion exchange, and other resins and gels used to preconcentrate analytes or remove matrix effects prior to atomic spectrometric detection have been reviewed by Hill and co-workers ( M 2 ) . Thermospray introduction AAS was reviewed by Koropchakand Veber ( M 3 ) . Two general reviews of LC/AAS were also published by Duneman ( M 4 ) and by Donard and Martin ( M 5 ) . A simple gaslliquid separator is presented by Schulze, Rybczynski, and Lehmann ( M 6 )which works for eluent flow rates up to 10 mL/min for HPLC-hydride AAS. Laborda et a!. ( M 7 ) focused on the sampling procedure necessary to maximize sensitivity in the transfer of fractions to electrothermal AAS. Taylor and Synovec ( M 8 )used normal-phase LC/AAS to study copper speciation of jet fuels. A UV/ visible absorbance detector mounted in series monitored the gradient conditions. Astruc et al. ( M 9 ) used on-line electrothermal A A for the detection of butyltin compounds. Separation and A A detection of various cadmium ( M 1 0 )and 12R
Analytical Chemistry, Vol. 66,No. 12,June 15, 1994
arsenic species ( M I I-M14) were also reported. Flame trapping devices such as the slotted quartz tube are becoming more widespread, due to the increased sensitivity they afford. Atomic Emission Spectrometry (AES). Uden (M15) covered the development and status ofvarious chromatography AES configurations and discussed the sensitivity, selectivity, and dynamic ranges of the systems for given elements. The coupling of G C / L C with both ICP-AES and ICP-MS was reviewed by Hill, Bloxham, and Worsfold (M16), with emphasis on applications to real samples. An overview of the mating of the nonmetal detection capabilities of helium plasmas with LC and SFC is reviewed by Webster and Carnahan ( M 1 7 ) . Krull and Childress ( M 1 8 ) reviewed the interfacing of G C / H P L C with direct current plasma (DCP) emission spectroscopic detection for trace metal analysis and speciation. The prospects for alternating current plasma detection for G C / H P L C are discussed in a review by Barry, Colon, and Costanzo ( M 1 9 ) . Tarr, Zhu, and Browner (M2O) reported a microflow ultrasonic nebulizer with close to 100% transport efficiencies, resulting in good precision and reproducibility for Mn emission signals from ICP-AES. Mason et al. ( M 2 1 ) developed a moving band interface that evaporates HPLC solvent prior to analyte introduction to a microwave-induced plasma A E detector. Chlorine element selective detection limits are in the 0.1-1 ng/s range for various organic species. A spark emission spectrometer is described by Lucht and Salje (MZZ) which can analyze water samplescontaining0.1-10 000 mg/L Na, K, or Ca. The HPLC effluent at 20 wL/min is evaporated and guides as a vapor to the spark plasma. Colon and Barry ( M 2 3 )presented a helium alternating current plasmadetector. The instrument has been used with HPLC to detect arsenic and selenium species after postcolumn hydride generation, with detection limits from 45 to 60 pg/s. Degenerate Four-Wave Mixing (D4WM). Tong (M24, M 2 5 ) describes optical phase conjugation by D4WM as a sensitive analytical detection method suitable for traceconcentration measurements using simple capillary detector cells that can be easily interfaced to LC. Its detection sensitivity ( 10-l8 mol level) is comparable to or better than those of the most sensitive analytical methods, including laser fluorescence, and yet it can detect both fluorescing and nonfluorescing analytes. A single low-power argon ion laser can be used in a relatively simple and compact optical arrangement. Ion Mobility (IM). Ion mobility spectrometry measures the arrival time of ions in an electric field, providing both qualitative and quantitative information. Hill and co-workers ( M 2 6 ) reviewed GC-IM and SFC-IM for trace organic analysis. Corona spray IM for LC is also described. Shumate and Hill ( M 2 7 )used amines in a study to optimize thedetector and reported detection limits of 5 fmol/s. Light Scattering (Evaporative). Dreux and Lafosse ( M 2 8 ) published a general review of the evaporative light scattering detector (ELSD), detailing its advantages over the refractive index detector for LC and the flame ionization detector for SFC. Christie ( M 2 9 )reviewed optical and spectophotometric detectors, with special reference to ELSD. A computer simulation model was developed by Van der Meeren, Vanderdeelen, and Baert ( M 3 0 ) ,which predicts the
response of the ELSD. Mobile-phase flow rate and peak width have been found to be important parameters. Calibration curves corresponding to each peak within a chromatogram may be calculated, even for unknown compounds, thus allowing a reproducible and accurate quantitative estimation of all the species separated. Lafosse et al. (M31) studied compounds of pharmaceutical interest and found that the narrow spread of response factors provided direct raw quantitation of unknown samples in stability studies. Molecular Size (Light Scattering) Detector. Claes and co-workers (M32) reported the development of a small, lowcost, easy-to-use dynamic light scattering (DLS) instrument. A fast, software-based autocorrelator made it possible toobtain DLS measurements on-line during the separation of macromolecules by LC. Lago and Corti (M33) presented a novel on-line DLS system with matched four-angle light detection capable of giving enough sensitivity with a simple He/Ne laser source. Gradient elution ion-exchange chromatography and low-anglelaser light scattering photometry were interfaced by Mhatre and Krull (M34). Using the specific R I increment (dnldc) and the R I of the solvent used over the gradient range, the weight-average molecular weights of proteins were rapidly determined. A high-angle light scattering detector has been disclosed by Dollinger, Cunico, and Kunitani (M35),in which scattered monochromatic light is collected at angles of about 90'. Using scattered and incident light intensity information, along with weight concentration data from another detector, average molecular weights are found. Nuclear Magnetic Resonance (NMR). On-line coupling of proton N M R to HPLC is reviewed by Albert and Bayer (M36). HPLC-NMR is explored by Lancelin and Cleon (M37), who with injection volumes of 10-100 pL achieved detection limits of 0.5 Fmol in continuous flow and 0.05 pmol in stop flow. Hofmann and Spraul (M38) coupled LC to N M R by using an intermediate storage loop. Gorog, Balogh, and Gazdag (M39) demonstrate the usefulness of HPLCN M R in drug profiling. The possibilities of utilizing N M R for the identification and quantification of impurities with and without their isolation are discussed. Radioactivity. Rapkin (M40) argues that continuous monitoring of effluent has distinct advantages over liquid scintillation counting of fractions, despite the greater sensitivity and accuracy for low-activity measurement that statistical considerations suggest. Gorelick and Reeder (M41) used a phosphorus-32 postlabeling procedure in which labeled adducts were separated by HPLC and quantified by liquid scintillation counting. Reddy, Bleicher, and Blackburn (M42)used affinity chromatography to purify thymine glycol adducts prior to radioactivity detection. Raman. Chong, Mann, and Vickers (M43) describe a fiber-optic-based system for Raman detection in LC. The system provides on-the-fly acquisition of resonance Raman spectra with correction for sample absorption. The ability to recover quantitative information when there is no chromatographic resolution is demonstrated. Thermionic (Nitrogen/Phosphorus). Kientz et al. describe in a two-part report (M44, M45) the modification of a thermionic detector to microcolumn LC. The system was optimized by varying parameters such as air, hydrogen, and helium gas flow rates, as well as the rubidium source burner
rim distance. For the organophosphorus compounds tested, the detection limit was 10-20 pg/s phosphorus. Viscometry. By using R I and viscosity detectors in series for size-exclusion chromatography, Hoagland et al. (M46) were able to rapidly characterize polysaccharides. Weightaverage intrinsic viscosities, global and component radii of gyration, and molecular weights were determined.
LITERATURE CITED A. COLUMNS
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Papoff, P.; Glacomelll, A.; Onor, M. Mh". J. 1992, 46,385-98. Brinkman, U. A. T. Analusis 1992, 20, M22-M28. Thiebaut, D.: Rosset, R. J. Chromatogr. 1992, 626, 41-52. ItO, Y. J. ChrOt?WtW. Llh. 1992, 57A, A69-AI07. Joensson, J. A.; Mathlasson, L. Trends Anal. Chem. 1992, 77,106-14. Verlllon, F.; Qian, F. A n a l W 1992, 79, 271-7. Luque de Castro, M. D.;Valcarcel, M. J. Chromatogr. 1992,600,183-8. Poppe, H. J. Chrometog. Ubr. 1992, 57A, A151-A225. Yamamoto, H Baumann. J.; Ernl, F. Jchrometog*. 1992, 593, 313-9. Johnson, B. F.; Bramlage, J.; Dorsey, J. G. Anal. Chlm.Acta. 1991,255, 127-33. Grob. K.; Artho, A; Le Donne, P J. H@ Resdut. Chrometogr. 1992, 75, 71-4. Lee, H.K.; Hoffman, N. E. J. Chromatog Sc/. 1992, 30, 415-21. Louwerse, D. J.; Boelens, H. F. M.; Smk, H. C. Anal. Chim. Acta 1992, 256, 349-59. Hatanaka, T.; Ishlda, M. J. Chem. Eng. Jpn. 1992, 25, 78-83. Cretier, 0.; El Khabchl, M.; Rocca, J. L. J. Chromatcgr. 1992, 596, 15-25. Llu, G.; DJordJevlc, N. M.; Ernl, F. J. C h m a t o g . 1992, 592, 239-47. Mlura, J.; Manz, A. Watanabe, Y.; Miyahara, Y. Miyagl, H.; Tsukada. K. US. Patent 5132012 A, Juiy 21 1992. Gulllemln, C. L. Process Control Qua/. 1992, 3, 153-66. Ohara, H.; Hlraga, T.; Katasho, I.; Inuta, T.; Yoshlda, T. J. Ferment. Bhwng. 1993, 75, 470-3. Koropchak. J. A.; Allen, L.; Davis, J. M. Appl. Spectrosc. 1992, 46, 682-9. Moulder, R.; Bartie, K. D.; Clifford, A. A. Analyst 1991, 776, 1293-8. Engelhardt, H.; Zapp, J.; Kolla, P. Chrometographla 1991,32,527-37. Isobe. T.; Uchkte. K.; Taoka, M.; Shlnkal, F.; Manabe, T.; Okuyama, T. J. ChrOfT?atogr. 1991, 588, 115-23. Tena, M. T.; Unares, P.; Luque de Castro, M. D.; Valcarcel, M. C h m t o g r a p h h 1992, 33, 449-53. Oestman, C.; Bemgaard. A.; ColmsJoe,A. J. H&h Resdut. Chromatcgr, 1992. 75, 437-43. Grob, K.; Toenz, 8. J. H&h Res&. Chromatog, 1992, 15, 594-600. Mlncsovlcs. E.. Garaml, M. Tyihak, E. J. Plenar Chromatogr,--Mod. TLC im.4.299-303. --&bets,A. J.J.;Hupe.K.P.;Kok, W.T.;Brinkman,U.A.T.J. Chr-toq. 1992. 600. 163-73. Andresen..A. T.: Jacobsen. P. B.: Rasmussen. K. E . J. Chromatow. 1992, 575, 93-9. Brewster, J. D.; Maxwell, R. J.; Hampson, J. W. Anal. Chem. 1993, 65, 2137-40. &io; LiDasgupta, P. K. Anal. Chem. 1992, 64, 991-6. Gulllemln, C. L. Chemom. Intell. Lab. Syst. 1992, 77. 201-11.
-. -.
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13R
(633) Li, S; HamiRon,J. C.; Gemperline, P. J. Anal. Chem. 1992, 64,599-607. (634) Keller, H. R.; Massart, D. L.; Kiechie, P.; Erni, F. Anal. Chim. Acta 1992, 256, 125-31. (635) Bahowlck, T. J.; Synovec, R. E. Anal. Chem. 1992, 64, 489-96. (636) Waetzlg, H. Chromatographia 1992, 33, 218-24. (637) Peterson, K. L. Anal. Chem. 1992, 64, 379-86. C. DETECTORS
Jorgenson, J. W.; De Wit, J. Chem. Anal. 1992, 727, 395-425, Flelden, P. R. J. Chromatogr. Sci. 1992, 30, 45-52. Freeman, M. K.; Daunert, S.; Bachas, L. G. LC-GC 1992, 70,112, 114, 116, 118. Martin-Goldberg, M.; Raymer, J. H.; Voyksner, R. D.; Peilizzari, E. D. ASTM Spec. Tech. Publ. 1991, No. 7102, 203-44. Chau, Y. K. Analyst 1992, 777, 571-5. Hjerten, S.;Srichaiyo, T. U.S. 5114551 A, 19 May 1992. Obst, D.; Thietz, P Ger DD 294182 A5, 26 Sept 1991. Gaus, H.; Lipford, G. 8.; Wagner, H.; Heeg, K. J. Immunol. Methods 1993, 758,229-36. Schmitt, J. F.; Guthridge, M.; Economou, C.; Bertolini, J.; Hearn, M. T. W. J. Biochem. Blophys. Methods 1992, 24. 119-33. Satoh, C.; Yamasaki, Y.; Chen, S. H. Proc. Natl. Acad. Asakawa, J. I.; Sci. U.S.A. 1992, 89, 9126-30. Iig, M.; Maier-Rosenkranz, J.; Mueller, W.; Albert, K.; Bayer, E.; Hoepfei, D. J. Magn. Reson. 1992, 96, 335-44.
D. ABSORBANCE DETECTORS (Dl) (D2) (D3) (D4) (D5) (D6) (D7) (D8) (D9) (D10) (D11) (D12) (D13) (D14) (D15) (D16) (017) (D18) (D19)
Tran,C. D. I n WLCDetection; Patonay, G., Ed.; VCH: New York, 1993; pp 111-26. Pchelkin, V. P.; Vereshchagin, A. G. A&. Chromatogr. 1992, 32, 87129. Castledine, J. 8.; Fell, A. F. J. Pharm. Biomed. Anal. 1993, 7 7 , 1-13. Rosenzweig, Z.; Yeung, E. S. J. Chromatogr. 1993, 645, 201-7. Djordjevic, N.; Stegehuls, D.; Liu, G.; Erni, F. J. Chromatogr. 1993, 629, 135-41. Castledine, J. 6.; Fell, A. F.; Modin, R.; Selberg. B. J. Chromatogr. 1993, 626, 127-34. Lu, D. S.; Feng, W. Y.; Ling, D. H.; Hua, W. 2. J. Chromatogr. 1993, 623, 55-62. Jinno, K.; Mlyashita, Y.; Sasaki, S.; Fetzer, J. C.; Biggs, W. R. fnviron. Monit. Assess. 1992, 19, 13-25. Cela, R.; Lores, M.; Garcia, C. M. J. Chromatogr. 1993, 626, 117-26. Lin, L. A. J. Chromatogr. 1993, 632, 69-78. Bounoshita, M.; Hibi, K.; Nakamura, H. Anal. Sci. 1993, 9, 425-8. Lurie, I.S.; Cooper, D. A.; Krull. I.S. J. Chromatogr. 1993, 629, 14351. Jackson, P. E.; Bowser, T. J. Chromatogr. 1992, 602, 33-41. Pastore, P.; Boaretto, A.; Lavagnini. 1.; Dlop, A. J. Chromatogr. 1992, 597, 219-24. Hrdiicka, A.; Havei, J.; Valiente, M. J. High Resolut. Chromatogr. 1992, 75. 423-7. Li, J. B. LC-GC 1993, IO, 856-8, 860, 862, 864. Castledine, J. 6.; Fell, A. F.; Modin, R.; Seiberg, B. J. Pharm. Biomed. Anal. 1992, 9, 619-24. Wang, Y.; Kowalski, B. R. Anal. Chem. 1993, 65, 1174-80. YaU, W. W.; Rementer, S.W.; Boyajian, J. M.; DeStefano, J. J.; Graff, J. F.; Lim, K. 6.; Kirkland. J. J. J. Chromatogr. 1993, 630, 69-77.
E. CHEMILUMINESCENCEDETECTORS
Stanley, P. E. J. Blolumln. Chemilumln. 1992, 7, 77-108. Hage, D. S. I n HPLC Detection; Patonay, G., Ed.; VCH: New York, 1992; pp 57-75. Gooijer, C. Schreurs, M.; Velthorst, N. H. I n HPLC Detection; Patonay, G., Ed.; VCH: New York, 1992; pp 27-55. WorsfoM,P. J. I n BiolumlnescenceandChemiluminescence,Procwdlngs ofthe InternationalSymposlum, 6th; Stanley, P. E., Kricka, L. J., Eds.; Why: Chlchester, 1991; pp 371-8. Rozhitskii, N. N. Zh. Anal. Khim. 1992, 47, 1765-93. Mahuzier, G.; Prognon, P.; Sargi, L.; Kouwalti, H.; Tod, M.; Farinotti, R . Ann. Pharm. Fr. 1993, 57, 135-53. Kwakman, P. J. M.; De Jong, G. J. Methodol. Surv. Blochem. Anal. 1992, 22, 261-8. Bryan, P. D.; Capomacchia, A. C. J. Pharm. Biomed. Anal. 1991, 9, 855-60. Hayakawa, K.; Mlnogawa, E.; Yokoyama, T.;Miyazaki, M.; Imai, K. Biomed. Chromatogr. 1992, 6. 84-7. Suglura, M.; Kanda, S.; Imai, K. Blomed. Chromatogr. 1993, 7, 149-54. Conboy, J. J.; Hotchklss, J. H. U S . 5094815 A, 10 Mar 1992. Fujinari. E. M.; Courthaudon, L. 0. J. Chromatogr. 1992, 592, 209-14. Brune, S. D.; Bobbin, D. R. Anal. Chem. 1992, 64, 166-70. Niederlander, H. A. G.; Engelaer, F. W.; Goojier, C.; Veithorst, N. H. I n Bioluminescence and Chemiluminescence, Proceedings of the International Symposlum, 6th; Stanley, P. E., Kricka, L. J., Eds.; Wiley: Chichester, 1991; pp 227-30. Fu, C.; Xu, H.: Wang, 2 . J. Chromatogr. 1993, 634, 221-7. Hanaoka, N.; Tanaka, H. J. Chromatogr. 1992, 634, 129-32.
(F45) (F46) (F47) (F48)
0. FLUORESCENCE DETECTORS (Gl) (G2) (G3) (G4) (G5) (G6) (G7) (G8) (G9) (G10) (G11) (G12) (G13) (G14) (G15)
F. ELECTROCHEMICALDETECTORS
(F1) (F2)
14R
Wang, J. I n HPLCDetection: Patonay, G., Ed.; VCH: New York, 1992; pp 91-109. Stulik. K. Anal. Chim. Acta 1993, 273, 435-41.
Analytical Chemistry, Vol. 66, No. 12, June 15, 1994
LaCourse, W. R. Analusis 1993, 27, 181-95. Johnson, D. C.: Lacourse, W. R. Electroanalysis 1992, 4, 367-80. Marko-Varga. G. A. Electroanalysis 1992, 4, 403-27. Bond, A. M. J. Chromatogr. Libr. 1991, 47, 187-211. Kilts, C. D. I n Neuroendocrinologx Nemeroff. C. B., Ed.; CRC: Boca Raton, FL, 1992; pp 51-61. Wang, E. Anal. Scl. 1991, 7, 1437-42 Maruyama, M. Fresenlus' J. Anal. Chem. 1992, 343, 890-2. Boussenadji. R.; Dufek, P.; Porthault, M. LC-GC 1993, 17, 450, 452, 454. Svendsen, C. N. Analyst 1993, 778, 123-9. Aoki, A.; Matsue, T.; Uchida, I . Anal. Chem. 1992, 64, 44-9. Takai, N.; Shinozuka, N.; Mashige, F.; Ohkubo, A.; Nukina, N.; Iijima, S.;Fukui, Y.; Sakuma, I.;Ito, A. Int. Conf. Ser.-Excerpta Med. 1992, 997, 157-9. Khaled, M. Y.; Anderson, M. R.; McNair, H. M. J. Chromatogr.Sci. 1993, 37, 259-64. Sorrels, J. W.; Dewald, H. D. Nectroanalysis 1992, 4, 487-93. Brown, G. N.; Birks, J. W.; Kovai, C. A. Anal. Chem. 1992, 64, 427-34. LaCourse, W. R.; Johnson, D. C. Anal. Chem. 1993, 65, 50-5. Mattusch, J.; Welsch, T.; Werner, G. J. Prakt. Chem./Chem.-Ztg.1992, 334, 49-52. White, J. G.; Soli, A. L.; Jorgenson, J. W. J. Liq. Chromatogr. 1993, 76, 1489-96. Righezza, M.; Siouffi, A. M. Analusis 1992, 20, 333-40. De Backer, B. L.; Nagels, L. J.; AMerweireidt, F. C.; Van Bogaert, P. P. Anal. Chim. Acta 1993, 273, 449-56. Long, J. T.; Weber, S. G. Nectroanalysis 1992, 4, 429-37. Loub, L.; Opekar, F.; Pacakova, V.; Stulik, K. Electroanalysis 1992, 4, 447-5 1. Mattusch,J.; Knauer, H.; Noack, J.; Ehrhardt,H.; Findeisen, B. Ger. DD 297250 A5. 2 Jan 1992. Carabias-Martinez, R.; Becerro-Dominguez, F.; Martin-Gonzaiez, F.; HernandezMendez, J.; Cordova-Oreilana,R. Anal. Chim. Acta 1993, 279, 299-307. Takahashi, M.; Morita, M.: Niwa, 0.; Tabei, H. J. flectroanal. Chem. 1992, 335, 253-63. Takahashi, M.; Morita. M.; Niwa, 0.;Tabei. H. Sens. Actuators, B 1993, 13. ., 336-9 --- - . Huang, X.; Kok, W. T. Anal. Chim. Acta 1993, 273, 245-53. Casella-Innocenzo, G.; Desimoni, E.; Rotunno, Cataldi-Tommaso, R. I.; T. Anal. Chim. Acta 1992, 270, 161-71. Zhou, J.; Wang, E. Nectroanalysis 1992, 4, 183-9. Zhou, J.; Wang, E. Talanta 1992, 39, 235-42. Zhou, J.; Wang, E. Taianta 1993, 40, 943-8. Fung, Y. M.; Saunders, P. Chem. Aust. 1993, 60, 278-80. Magee, L. J., Jr.; Osteryoung, J. G. US. 5118403 A, 2 Jun 1992. Marioli, J. M.: Kuwana, T. Electroanalysis 1993, 5, 11-15. Sagar, K. A.; Hua, C.; Kelly, M. T.; Smyth, M. R. Nectroanalysis 1992, 4, 481-6. Martens, 0. A.; Frankenberger,W. T., Jr. J. Liq. Chromatogr. 1992, 75, 423-39. Gamache, P.; Ryan, E.; Svendsen, C.; Murayama, K.; Acworth, I.N. J. Chromatogr. Blomed. Appl. 1993, 674, 213-20. Krull, I.S.;Dou, L. Cuff. Sep. 1992, 7 7 , 7-11. Dou, L.; Kruii, I.S. Electroanalysls 1992, 4, 381-91. Soucaze-Guilious, 6.; Kutner, W.; Kadish, K. M. Anal. Chem. 1993, 65, 669-72. Robecke, M.; Cammann, K. Fresenius'J. Anal. Chem. 1991,347,5558. Rose, M.; Shearer, G. J. Chromatogr. 1992, 624, 471-7. Yao, T. GBF Monogr. 1991, 14, 217-24. Bergens, A. J. Chromatogr. 1992, 598, 195-201. Wang, E.; Liu, A. Mlcrochem. J. 1991, 44, 327-34. Berglund, I.; Dasgupta, P. K. Anal. Chem. 1992, 64, 3007-12. Dasgupta, P. K.: Lopez, J. L.; Nara, 0. Anal. Chem. 1993, Berglund, I.; 65. 1192-8.
(G16) (G17)
Edkins, T. J.; Shelly, D. C. I n HPLC Detection; Patonay, G., Ed.; VCH: New York, 1992; pp 1-26. Rahavendran, S.V.; Karnes, H. T. Pharm. Res. 1993, 70,328-34. Mank, A. J. G.; Lingeman, H.; Gooijer, C. Trends Anal. Chem. 1992, 7 1 , 210-7. Coquet, A.; Veuthey, J. L.; t:aerdi, W. Chromatographla 1993, 34, 651-4. Sweedier, J. V.; Shear, J. 6.; Zare,R. N. U.S. 5141609A, 25Aug 1992. Mank. A. J. G.; Molenaar, E. J.; Lingeman, H.; Gooijer, C.; Brinkman, U. A. T.; Velthorst, N. H. Anal. Chem. 1993, 65, 2197-203. Lehotay, S. J.; Pless, A. M.; Winefordner, J. D. Anal. Sci. 1992, 7, 863-71. Imasaka, T.; Nishitani, K.; Ishibashi, N. Analyst 1992, 7 76, 1407-9. Abbas, A. A.; Shelly, D. C. J. Chromatogr. 1993, 637, 133-44. Bostlck. J. M.; Strojek. J. W.: Metcalf, T.; Kuwana, T Appl. Spectrosc. 1992, 46, 1532-9. Williams, T.; Barnen, N. W. Anal Chim. Acta. 1992, 264, 297-301. Ramos, B. L.; Mike, J. H. Mlcrochem. J. 1993, 47, 33-40. Yoshida, T.;Moriyama, Y.; Tanlguchi, H. Anal. Sci. 1992, 8, 355-9. Toyooka, T.; Ishibashi, M.; Terao, T. Analyst 1992, 777, 727-33. Kondo, J.; Imaoka, T.; Kawasaki. T.: Nakanishi. A,; Kawahara. Y. J. Chromatogr. 1993, 645, 75-81. Sharma, M.; Freund. H. G. Proc. SPIE-Int. SOC.Opt. Eng. 1992, 7435, 280-9 1. Iwaki. K.; Okumura. N.; Yamazaki. M. J. Chromatogr. 1992, 623, 1538.
(G18) Iru1, H.; Oosterkamp, A. J.; van der Welle, W.; Tjaden, U. R.; van der Greef, J. J. Chromtogr. 1993, 633, 65-72. (019) Schneede, J.; Ueland, P. M. Anal. Chem. 1992, 64, 315-19.
Da cd,R.; Slhrestro,L.; Bakcchl,C.; Glacosa,D.; Viano, I. J. C hfvmaw. wsa, 633,119-28. McLaughlln, L. 0.; Henlon, J. J. Chfomatm. 1982, 591, 195-206. Jaquincd. M.; Van Do”, A. A n a h & 1992, 20,407-12. Juhasz, P.;Ikonomu, M. G.; Blades, A. T.; Kebrale, P. NATO AS: Ser. 1991, 269, 171-84. Perklns, J. R.; Parker, C. E.; Tomer, K. 8. J. Am. Soc. Mass Specbom. 1992, 3,139-49. Lee, E. D.; Henion, J. D. RapM Commun. Mass Spectrom, 1992, 6,
H. INDIRECT DETECTION Glavina, L. L. M.; Cantwell, F. F. Anal. Chem. 1993, 65, 266-76 Kawazumi, H.; Nishimwa, H.; Ogawa, T. J. Llq. Chromabgr. 1992, 15, 2233-45. Kaijurand,M.; Urbas, E.; Haldna, U. Chromatographla 1992,34417-20 Tunuii, M. S. Talenta 1992, 39, 85-90. 1992, 15, 2611-22. Groh, T.; Baechmann, K. J. Liq. Chroma-, Mlchigaml, Y.; Yamamoto, Y. J. Chromatcgf. 1993, 623. 148-52. Zou, J.; Motomizu, S.; Fukutomi, H. Analyst 1992, 116, 1399-405. 1982, 14, 2835-57. Yuan, D.; Pietrzyk, D. J. J. LiquM Chroma-. Makl, S.A.; Wangsa, J.; Danielson, N. D. Anal. Chem. 1992, 64,583-9.
727-33.
Ailen,M. H.;Shushan,B. I. LCOC, 1893, 11, 112-4, 116. 118, 120-2, 124, 126. Thomson, 8. A.; Ngo, A.; Shushan, B. I.I n Insbumentatlon br Trace &pk MhfhgClament, R. E., Siu. K. W. M., Mi H., Jr.. Eds., Lewis: Chelsea, MI, 1992 pp 209-17. Duffln, K. L.; Wachs, T.; Henion, J. D. Anal. Chem. 1992, 64, 61-8. Heltkemper, D. T.; Caruso, J. A. J. Chrmmfogr. Llbr. 1891,47,49-73. Hill. S.J.: Bbxham, M. J.: Worsfold, P. J. J. Anal. At. Smtrom. 1993, 8, 499-515. Vela, N. P.; Olson, L. K.; Caruso, J. A. Anal. Chem. 1993, 65, 585A592A, 586A-597A. Olson, L. K.; Heitkemper, D. T.; Caruso. J. A. ACS Symp. Ser. 1992, No. 479, 288-308. Owen, L. M.; Crews, H. M.; Hutton, R. C.; Waish, A. Analyst 1992, 117. 649-55. Braverman, D. S . J. Anal. At. Specfrom. 1982, 7, 43-6. Shum, S. C. K.; Neddersen,R.; Houk, R. S. Analyst 1992, 117,577-82. Beckett, R. At. Specbosc. 1991, 12, 228-32. Krost, K. J. Appl. Spectrosc. 1983, 47, 821-9. Perreault, H,; Ramaley, L.; Slm. P. 0.;Benoit, F. M. RapM Commun. Mass Specbom. 1991, 5, 604-10. Snodgrass, 641, 396-9.J. T.; Hayward, M. J.; Thomson. M. L. J Chroma-. 1993,
I.INFRARED DETECTORS
Fujimoto, C.; Jinno, K. Anal. Chem. 1992, 64. 476A-81A. Kalasinsky, V. F.; Kalasinsky. K. S. I n HPLC DefecfbqPatonay, G., Ed.; VCH: New York, 1992; pp 127-61. Patonay, G.; Czuppon, T. I n HPLC Datectbq Patonay, G., Ed.; VCH: New York, 1992; pp 77-90. Meyer, U.; Salzer, R.; Raddatz, J. Makromol. Chem., Macromol. Symp. 1991. 52, 261-8. Aklyama, S. Chem. Anal. 1993, 77, 229-51. Robertson, A. M.; Littlejohn, D.; Brown, M.; Dowle, C. J. J. Chromatogr. 1991, 588, 15-24. DiNunzlo, J. E. J. Chromatog. 1992, 626, 97-107. Griffiths, P. R.; Lange, A. J. J. Chromatcgf. Scl. 1992, 30, 93-7. Lange, A. J.; Griffiths, P. R. Appl. Specfrosc. 1993, 47, 403-10. Lam, C. K. Y.; Zhang, Y.; Busch. M. A.; Busch. K. W. Talanta 1993, 40. .-, 887-78 - - . . -. Tilotta, D. C.; Lam, C. K. Y.; Busch, K. W.; Busch. M. A. Appl. Specfrosc. 1993, 47, 192-200.
Steiner, V,; Boernsen, K. 0.; Schaer, M.; Gassmann, E.; HoffstetterKuhn, S.; Rink, H.; Mutter, M. Pept. Res. 1992, 5, 25-9. Oguri. N.; Onishl, A.; Uchlno, S.; Hashlmoto, K.; Jin, X. ShltswyoBunsdrI 1992, 40. 33-9. Hsu, C.; Qlan, K. Anal. Chem. 1983, 65, 761-71.
J. LC/MS
Jinno, K.; Uemura,T.; Nagashima, H.; Itoh, K. J. H@~Resolut. Chmafcgf. 1992, 15, 627-8. Tomer, K. I n HPLCDatectkw Patonay, G., Ed.; VCH: New York, 1992; pp 163-95. Van der Greef, J.; Nlessen, W. M. A. Int. J. MassSpecbm.Ion Rocesses 1982, 118-9, 857-73. Barcelo. D. Anal. Chlm. Acta 1992, 263, 1-19. Niessen, W. M. A.; Tjaden, U. R.; Van der Greef, J. Methodo/. Surv. Biochem. Anal. 1992. 22, 253-80. Budzikiewlcz, H. Mass Specfrom. Rev. 1991, 10, 453-6. Kaudewitz, H. Laborpraxis 1992, 16. 730-3. Arpino, P. J. NATO ASI Ser.1992, 353, 253-67. Ikal, Y.; Oka. H.; Hayakawa,J.; Harada,K.; Suzukl, M. ShitswyoBunseki 1991, 39, 199-204. Lawrence, D. J. Am. SOC. Mass Specfrom, 1892, 3, 757-81. cs Melbn, F. A. I n R c d u c t b n a n d W b k a M w , o f L ~ ~ b s i[Rvceddhgs o f a Workshop];Gakketti, G., Ed.; Elsevier: London, 1991; pp 151-62. Lecoq, A. F.; Di Blase, S.; Montanarella, L. J. Chromafogr. 1993. 638, 363-73. Kuksis, A.; Meral, L.; Myher, J. J. J. Chromatogr. 1991. 588, 73-87. Carrier, A.; Qagne, J. P.; Bertrand, M. J. J. Chromatop. 1992, 591, 129-37. McLean, T.; New. A. P.; Haskins, N.; Camilleri. P. J. Chem. Soc.,Chem. Commun. 1982, 24, 1773-5. Arpino, P. Mass Specfrom. Rev. 1892, 11, 3-40. East, P. B.; Eckers, C.; Haskins, N. J.; Hare, J. F.; James, P. J. RapM Commun. Mass Specfrom. 1992, 6, 179-83. Hau, J.; Nigge. W.; Llnscheid, M. Org. Mass. Specfrom. 1993,28,2239. Van der Hoeven, R. A. M.; Nlessen, W. M. A.; Schols, H. A.; Brugglnk, C.; Voragen, A. G. J.; Van der Greef, J. J. Chromatogr. 1992, 627, 63-73. Van Leuken, R. 0. J.; Kwakkenbos, G. T. C. J. Chromafogr. 1992, 626, 81-6. Vreeken, R. J.; Van Dongen. W. D.; Ghijsen, R. T.; De Jong, G. J.; Lingeman, H.; Brlnkman, U. A. T.; Van Leuken, R. 0. J.; Kwakkenbos. G. T. C.; Deelder. R. S. Bbl. Mass. Specfrom. 1992, 21, 305-14. Kanohta, K. Anal. Scl. 1991, 7 , 1507-10. Hsu, F. F. Bbl. Mass. Specfrom. 1992, 21, 363-4. Bier, M. E.; Winkler, P. C.; Herron, J. R. J. Am. Soc. Mass Spectrom. 1993, 4, 38-48. Apffel, J. A., Jr.; Nordman, R. G.; Martlch, M. EP 538930 A l , 14 Apr 1992. Behymer. T. D., Beiiar, T. A.; Ho, J. S.; Budde. W. L. Or@nohalogen Compd. 1990, 2, 99-102. Ho, J. S.; Behymer, T. D.; Budde, W. L.; Beliar, T. A. J. Am. Soc.Mass Specfrom. 1992, 3, 682-71. Hsu, J. Anal. Chem. 1882, 64, 434-43. Capplelo, A.; Bruner, F. Anal. Chem. 1883, 65. 1281-7. Doerge, D. R.; Burger, M. W.; Bajic, S. Anal. Chem. 1892, 64, 1212-6. Chipman, 0. R.; Crulckshank, K. A. J. Chroma-. 1891, 554, 141-8. Kleintop, B. L.; Eades, D. M.; Yost, R. A. Anal. Chem. 1993, 65, 12951300. Hopfgartner, G.; Wachs, T. Bean, K.; Henion. J. Anal. Chem. 1993, 65, 439-48. Conboy, J. J.; Henion, J. Bbl. Mass Spectrom. 1992, 21, 397-407.
K. OPTICAL ACTIVITY DETECTORS (Kl) (K2) (K3) (K4)
(K5) (K6) (K7)
(K8)
Salvadori, P.; Bertucci, C.; Rosini, C. ChkaMy 1991, 3. 376-85. Mannschreck, A. Chiralky 1992, 4, 163-9. Zukowski, J.; Tang, Y.; Berthod, A.; Armstrong, D. W. Anal. Chlm. Acta 1992, 258, 83-92. Goodall, D. M.; Robinson, N. A.; Wu, 2. J. Chromatogr. Scl. 1893, 31. 133-6. Brooks, D. J.; Perklns, M. J.; Smith, S. L.; Goodall, D. M.; Lloyd, D. K. J. Chem. Soc.,Perkln Trans. 2 1992, 3, 393-6. Zelenka, W.; Leiminer, A.; Mannschreck, A. GITFachz. Lab. 1993,37, 97-8, 101-3. Brandl, G.; Kasmer, F.; Mannschreck,A.; Noekhg, B.; Andert, K.; Wetzei. R. J. C h r m f c g f . 1991, 586, 249-54. Kawaruml, H.; Nlshlmura. H.; Otsubo, Y.; Ogawa, T. Anal. Scl. 1991, 7, 1479-80.
L. REFRACTIVE INDEX DETECTORS (L1) (L2) (L3) (L4)
Kolbert, J. H. U.S. 5139661 A, 16 Aug 1992. Mharte, R.; Krull, I . S. Anal. Chem. 1993, 65, 283-6. Lima 111, L. R.; Synovec, R. E. Anal. Chem. 1993, 65, 128-34. Murugalah, V.; Synovec, R. E. Anal. Chem. 1992, 64, 2130-7.
M. MISCELLANEOUS DETECTORS
(Ml) (M2) (M3) (M4) (M5) (M6) . . (M7) (M8) (M9)
(M10) (Mll) (M12) (M13) (M14) (M15) (M18) (M17) (M18) (Ml9) (M20) (M21)
Klaentschi, N. Chlmle 1992, 46,186-99. Ebdon, L.; Fisher, A. S.; Hill, S. J.; Worsfold, P. J. J. A M . Chem. 1991, 13, 281-6. Koropchak, J. A.; Veber, M. Crk Rev. Anal. Chem. 1992,23,113-41. Duneman. L. Freseniw‘ J. Anal. Chem. 1892, 342, 802-4. Donard, 0. F. X.; Martin, F. M. Trends Anal. Chem. 1992, 11, 17-26. Schulze, G.; Rybczynski, H.; Lehmann, C. Fmsenlw’ J. Anal. Chem. 1992, 342, 192. . Labada, F.;Chakraborti, D Mir. J. M.;Casth, J. R. J. Anal.At. S p e c ” , 1993. 8, 643-8. Taylor, D. B.; Synovec, R. E. Talanta 1883, 40, 495-501. Astruc, A.; Astruc, M.; Pinei, R.; Potin-Gautler, M. Appl. &@nomet. Chem. 1992, 6, 39-47. Klaassen, C. D.; Lehman-McKeeman, L. D. Methods € n z y d . 1991, 205, 190-8. Larsen, E. H.; Honore Hansen, S. Mikroch/m. Acta 1992. 709, 47-51. Honore Hansen. S.;Larsen, E. H.; Prkl, 0.; Cornett, C. J. Anal. At. Specfrom. 1992, 7, 629-34. Hakala, E.; Pyy, L. J. Anal. At. Spectrom. 1982, 7, 191-6. Arenas, C.; Victor, J. Forschungszent. Jueiich Ber., Juel2512, 1991. Wen. P. C. ACS Symp. Ser. 1992, 479, 1-24. Hill, S.J.; Bloxham, M. J.; Worsfold, P. J. J. Anal. At. Specbom. 1993, 8. 499-515. Webster, G. K.; Carnahan. J. W. ACSSymp. Ser. 1992. No. 479.25-43. Krull, I. S.;Chlldress. W. J. Chromatog. Lib. 1891, 47, 239-87. Barry, E. F.; Colon, L. A.; Costanzo, R. B. ACS Symp. Ser. 1992, No. 479, 170-88. Tan, M. A.; Zhu, 0.; Browner, R. F. Anal. Chem. 1993, 65, 1689-95. Mason, P. B.; Zhang, L; Carnahan, J. W.; Wlnans, R. E. Anal. Chem. 1993, 65, 2596-600.
Analj.ical Chemistry, Vol. 66,No. 12, June 15, 1994 0 15R
Lucht, H.;Salje, G. Laborpraxis 1002, 16, 21-4, 26. Colon, L. A.; Barry, E. F. J. High Resoiut. Chromtogr. 1001, 14, 60812. Tong, W. G. Roc. Int. Conf. Lasers, 14th 1001, 816-20. Tong, W. G. Roc. SPIE-Int. SOC.Eng. 1002, 1637, 25-32. Hill, H. H.,Jr.; Siems, W. F.; Eatherton, R. L.; St. Louis, R. H.; Morrissey, M. A.; Shumate, C. B.; McMinn, D. G. I n Instrumentation for Trace OrganlcMonitoring,Clement, R. E.,Ed.; Lewis: Chelsea, MI, 1992; pp 49-64. Shumate, C. 8.; Hill, H. H. ACS Symp. Ser. 1002, No. 506, 192-205. Dreux, M.; Lafosse, M. Anaiusis 1002, 20, 587-95. Christie, W. W. I n Advances in Lipid Methodology-One; Christie, W. W., Ed.; Olly Press: Ayr, UK, 1992; pp 239-71. Van der Meeren, P.; Vanderdeelen, J.; Baert, L. Anal. Cbem. 1002, 64, 1056-62. Lafosse, M.; Elfakir, C.; Morln-Allory, L.; Dreux, M. J. High Resoiut. Chromatogr. 1002, 15, 312-18. Claes, P.; Dunford. M.; Kenney, A.; Vardy, P. Spec. Pub/.-R. SOC. Chem. 1002, No. 99, 66-76. Lago, P Corti, M. Conf. floc.-Itai. Phys. SOC.1001, 29, 351-4. Mhatre, R. M.; Krull, I . S . J. Chromatogr. 1002, 591, 139-48.
l6R
Analytical Chemistry, Vol. 66,No. 12, June 15, 1994
(M35) Dolllnger, G. D.; Cunico, R. L.; Kunitani, M. G. PCT In!. Appl. WO 9207244 AI, 30 Apr 1992. (M36) Albert, L.; Bayer. E. I n HPLC Detection; Patonay. G., Ed.; VCH: New York, 1992; pp 197-229. (M37) Lancelin, P.; Cleon, P. Spectra 2000 1001, 161, 33-41. (M38) Hofmann, M.; Spraui. M. Ger. DE 4104075 C1, 19 Mar 1992. (M39) Gorog, S.;Balogh, G.; Gazdag, M. J. Pharm. Biomed. Anal. 1001, 9. 829-33. (M40) Rapkin, E. J. Liq. Chromatogr. 1003, 76, 1769-81. (M41) Gorelick, N. J.; Reeder, N. L. Environ. Health Perspect. 1003,99, 20711.
(M42) Reddy, M. V.; Bleicher, W. T.; Blackburn, G. R. CancerCommun. 1001, 3, 109-17. (M43) Chong, C. K.; Mann, C. K.; Vickers, T. J. Appl. Spectrosc. 1002, 46, 249-54. (M44) Kientz, Ch. E.; Verweij, A.; de Jong, G. J.; Brinkman, U. A. Th. J. Chromatogr. 1002, 626, 59-69. (M45) Kientz, Ch. E.; Verweij, A.; de Jong, G. J.; Brinkman, U. A. Th. J. Chromatogr. 1002, 626, 71-80. (M46) Hoagland, P. D.: Fishman, M. L.; Konja. G.: Clauss, E. J. Agric. Food Chem. 1003, 47, 1274-81.
