Anal. Chem. 1996, 68, 587R-598R
Column Liquid Chromatography: Equipment and Instrumentation L. David Rothman
Analytical Sciences Laboratory, The Dow Chemical Company, 1897B Building, Midland, Michigan 48667 Review Contents Columns Supports Bonded Stationary Phases Polymeric HPLC Phases Micro- and Minicolumns Other Articles of Interest Instrumentation Hyphenated Instrumentation LC-on-a-Chip Sample Preparation Other Methods Elemental Detectors Reviews Flames Inductively Coupled Plasma Microwave-Induced Plasma UV/Visible IR, and Raman Detectors UV/Visible Infrared Raman Fluorescence Detectors Chemiluminesence Detectors Mass Spectrometry Detectors Reviews Other Articles Electrochemical Detectors Microelectrodes and Microcolumns Amperometry Carbohydrate Detection Other Articles NMR Detectors Other Detectors Thermooptical Detectors Optical Activity Detectors Surface Plasmon Resonance Light Scattering Detectors Gas Chromatography Detectors in LC Other Detectors Computation Reviews Diode-Array Detector Data Interpretation Column Selection Other Papers Literature Cited
587R 587R 588R 588R 589R 589R 589R 589R 590R 590R 590R 590R 590R 590R 590R 590R 590R 590R 591R 591R 591R 591R 591R 592R 592R 592R 592R 593R 593R 593R 593R 593R 593R 593R 594R 594R 594R 594R 594R 594R 594R 594R 595R 595R
This review covers fundamental developments in the field of column liquid chromatography (LC) equipment and instrumentation between October 1993 and October 1995. Readers will note a few articles with publication dates prior to this period, but these were in journals not abstracted until after the close of the period covered by the previous review on this subject. This review is not intended to cover applications; rather, applications are only mentioned in relation to demonstrating performance of equipment. S0003-2700(96)00009-1 CCC: $25.00
© 1996 American Chemical Society
The main data base for the review was Chemical Abstracts. This is not a comprehensive review of all the literature dealing with LC equipment and instrumentation. Coverage was limited to English language articles in refereed publications. Due to the close relationship between capillary column LC and capillary electrophoresis, there are references on technology which apply to both. In some cases, the application to LC is not yet demonstrated, but the article is referenced because the technique appears likely to interest capillary LC practitioners. Readers will find two references to publications available only through the World Wide Web (A21 and K15), a relatively recent addition to the world of literature. Accessibility of these Web pages was confirmed upon submission of the draft of this review, but the likelihood of continued availability of this information is unknown. There is a great deal of information published on LC hardware, equipment, troubleshooting, hints, tips, tricks and instruments in publications such as LC-GC, American Laboratory, R&D Magazine, Chemical & Engineering News and similar periodicals. The reader is referred to these for very up-to-date information on new commercial equipment for LC. For example, LC-GC and Chemical & Engineering News usually have articles each year covering new equipment, columns, and instruments for chromatography shown at the Pittsburgh Conference on Analytical Chemistry. Such publications are not covered in this review. COLUMNS This section of the review covers references dealing with investigations of solid supports, bonded stationary phases, polymeric phases, column packing techniques and mini- and microbore columns. Supports. Two studies were published on the characterization of silica gel particle size distributions by field flow fractionation (FFF). Ratanathanawongs and co-workers (A1) used flow/ hyperlayer FFF and correlated results with scanning electron microscopy, while Pazourek and co-workers (A2) used gravitational FFF to effect the separations. Kaneko and co-workers (A3, A4) prepared mixed-oxide particles containing silica and described their behavior in LC separations. Loere and co-workers (A5) reported continued work on silica and polar-bonded phases on silica modified with camphorsulfonic acid. Lorenzano-Porras and co-workers (A6, A7) described the synthesis of porous zirconia supports by colloid-aggregation processes and the evaluation of these supports. Weber and co-workers (A8) evaluated the chromatographic performance of porous carbon-clad zirconia supports. Akama and Kanno (A9) demonstrated separations using cerium oxide as a support. Nagaoka and co-workers (A10, A11) described the preparation of spherical carbon supports less than 5 µm in diameter by graphitizing spherical cellulose particles. The resulting carbon beads are described as more similar in behavior to conventional bonded reversed-phase (RP) silica supports Analytical Chemistry, Vol. 68, No. 12, June 15, 1996 587R
(contrasted with conventional carbon particle supports), but with the expected chemical stability of a carbon support. Serys and co-workers (A12) described the preparation and characterization of cellulose-based adsorbents for hydrophobic interaction chromatography. Inoue and Ohtaki (A13) described pyrophosphates as packing materials for HPLC separations of biological materials. Petro and co-workers (A14) prepared silica-, poly(hydroxyethyl methacrylate)-, or carbon-based macroporous solid particles with pores filled by a soft dextran network and used them for inverse size-exclusion chromatography. Honda and co-workers (A15) used dry-impact blending to prepare irregularly shaped particles for HPLC column packings. Pesek and Tang (A16) prepared alumina, zirconia, thoria, and titania supports with a monolayer of silane, producing a surface that could be subsequently reacted with a terminal olefin to produce a series of stationary phases. Bonded Stationary Phases. Pesek and Williamson (A17) presented a review comparing a number of novel stationary phases and comparing them with the ideal properties of reversed-phase HPLC columns. Williams and Stalcup (A18) reviewed some of the more important developments in chiral separations with cyclodextrin-based stationary phases. Allenmark and Andersson (A19) reviewed the use of immobilized proteins for chiral separations. Kirkland and Henderson (A20) discussed the selectivity and retention characteristics of conformationally different alkyl bonded phases. Bolck and co-workers (A21) reported a statistical technique to study the aging process of reversed-phase HPLC columns. Montes and co-workers (A22) evaluated alkyl bonded phases prepared by olefin hydrosilation of a hydride silica intermediate, the support preparation referenced earlier (A16). Moriyama and co-workers (A23) evaluated the chromatographic properties of a new reversed-phase column, TSKgel Super ODS, with 2-µm spherical silica particles. They demonstrated performance with basic and chelating compounds. Schmid and coworkers (A24) described the synthesis and characterization of bonded phases containing unsaturated fatty acids and compared the performance of these to corresponding saturated hydrocarbon phases. Pesek and Matyska (A25) synthesized and characterized two different diol bonded phases, including one which is described as a “true” diol bonded phase, the latter by attaching 7-octene1,2-diol directly to the hydride silica supports this group had prepared (A16). Jinno and Nakamura (A26) evaluated fluorinated bonded silica as a reversed-phase support and described the selectivity as different from that found with conventional RP supports. Buszewski and co-workers (A27) compared alkylamide and alkyl bonded phase supports for RP separations and found the alkylamide phase useful for separation of polar species, but less thermally stable than the alkyl phases. Stalling and coworkers (A28) prepared resin and silica supports with chemically bound buckminsterfullerenes and described their application to the separation of polychlorinated biphenyls. Wongyai (A29) bonded phenylpropanolamine to silica to produce a mixed mode ion-exchange/reversed-phase support and evaluated its performance with a series of acidic, neutral, and basic solutes. Houbenova and co-workers (A30) evaluated performance of a commercial cyanopropyl phase, including hydrolytic stability. Friebe and coworkers (A31) bonded calixarene to silica and studied it as a selective phase capable of forming inclusion complexes similar to cyclodextrins. Chriswanto and co-workers (A32) coated polypyrrole-based phases on silica and characterized these as HPLC packings. Ge and co-workers (A33) synthesized poly(3-octade588R
Analytical Chemistry, Vol. 68, No. 12, June 15, 1996
cylpyrrole)-modified silica and evaluated it for protein separations, as well as studying its stability in acidic and basic media. Akapo and Simpson (A34) prepared reversed-phase supports in fluidized beds. They concluded that a more reproducible product could be prepared by this approach compared to conventional bonding procedures in organic solvents. Theinpont (A35) described an in situ process for derivatizing silica gel already packed in HPLC columns and compared columns prepared by this process to those with conventionally bonded phases. Murayama and co-workers (A36, A37) studied the stability of octadecyl titania to basic eluents. Sun and Carr (A38) discussed mixed-mode retention on phosphate-modified polybutadiene-coated zirconia. They described application of this phase to protein separations, which required mobile phases containing both an organic modifier and high concentrations of sodium perchlorate. Da and co-workers (A39) described preparation of nitrogen-containing crown ethers bonded to porous silicas. Polymeric HPLC Phases. Hanson and co-workers (A40) reviewed the synthesis and properties of polymer-coated reversedphase stationary phases. Petro and Berek (A41) published a review of HPLC stationary phases produced by creating a polymer layer on silica particles. Kataev and co-workers (A42) prepared silica particles coated with poly(trifluorostyrene) and demonstrated its performance for haloaryl compounds, peptides, and proteins. Zuo and co-workers (A43) prepared a series of polymerencapsulated materials for reversed-phase LC by polymerization of ethylbenzene and divinylbenzene with vinyl-modified silica. In November 1993, Majors (A44) discussed the polymeric packings for HPLC developed in Japan. There has been continued activity in producing these materials, not limited to that nation. Nagaoka and co-workers (A45) prepared and characterized poly(N,N-dialkylacrylamide) spherical packings. Hosoya and coworkers (A46) copolymerized glycerol monomethacrylate and glycerol dimethacrylate with cyclohexanol for pore size control to produce porous beads and demonstrated this phase with hydrophylic drugs. Smigol and co-workers (A47) produced poly(vinylphenol) porous beads, which allowed fast switching between size-exclusion, normal-phase, and reversed-phase separations. The same group (A48) also produced poly(glycidyl methacrylate-coethylene dimethacrylate) beads using a pore size-specific functionalization process and demonstrated these supports for LC separations of proteins, drugs, and small hydrocarbons. Ogawa and co-workers (A49) copolymerized maleic anhydride with divinylbenzene and produced 10-30-µm spherical beads which were hydrolyzed to a carboxylic acid resin. Sellergren (A50) discussed imprinted dispersion polymers as a new class of affinity stationary phases and demonstrated the performance of these with drug and herbicide substances. Hosoya and co-workers (A51) prepared macroporous poly(vinyl p-tert-butylbenzoate) beads and compared their performance to that of two other polymeric beads and a more conventional C18 HPLC stationary phase. Smigol and co-workers (A52) described monodisperse poly(glycidyl methacrylate-co-ethylene dimethacrylate) beads with pore size-specific functionalization to give a diol or diethylamino phase in the larger pores and an octadecyl function in the smaller pores, thus producing a support that limits access to the octadecyl phase to molecules small enough to enter the pores, while allowing all molecules access to a more polar phase. Chen and Shieh (A53) made cross-linked particles of poly[N-(1-phenylethyl)acrylamide] and evaluated them as HPLC supports. Freitag and co-workers
(A54) discussed the effect of bed compression on HPLC columns with gigaporous polymer packings. The conditions used during column packing were reported to have a substantial effect on eventual performance of the columns, most likely due to particle deformation. Hosoya and co-workers (A55) modified polymerbased packing materials with a temperature-sensitive polymer, poly(N-isopropylacrylamide). These phases were then investigated as a means to substantially alter column selectivity for drug separations by column temperature control. Wang and co-workers (A56) prepared porous rods of poly[(chloromethyl)styrene-codivinylbenzene] and evaluated these in the HPLC of small molecules and proteins. Svec and Frechet (A57) also prepared poly(glycidyl methacrylate-co-ethylene dimethacrylate) continuous rod columns (300 × 8 mm) for preparative-scale ion-exchange chromatography of proteins. They demonstrated the separation of 300 mg of a protein mixture in a single injection onto this column. Gawdzik and Matynia (A58) prepared cross-linked porous copolymer of methacrylic ester of (p,p′-dihydroxydiphenyl)propane diglycidyl ether and divinylbenzene as a new HPLC packing and evaluated it for normal- and reversed-phase separations. Ogino and co-workers (A59) prepared and characterized monodisperse oligo(ethylene glycol) dimethacrylate polymer beads for aqueous size-exclusion chromatography of proteins. Danielson and co-workers (A60) reacted Kel-F 800 with an (aminopropyl)silica support to produce a weak anion-exchange packing. Micro- and Minicolumns. Cole and co-workers (A61) discussed column designs that permit rapid separations with packed capillary LC columns. They studied the effect on plate height of column diameter, packing particle type, and the ratio of column inside diameter to particle diameter. The conclusion of this work was that a 50-µm-i.d. column packed with 8-µm particles was the optimum configuration, based on plates generated/s (700). St. Claire and co-workers (A62) prepared borosilicate glass capillary reversed-phase open tubular columns (20 µm i.d.) by reacting dimethyloctadecylchlorosilane with the etched inner walls. Goehlin and Larsson (A63) prepared open tubular reversedphase columns in fused silica tubing (5-50-µm i.d.) by immobilizing poly(methyloctadecylsiloxane) and evaluated these with anthracene test solutes. Crescentini and Mastrogiacomo (A64) dry-packed 250-µm-i.d. fused-silica capillaries with a range of silica and silica-based bonded phase supports. They compared these to similar columns prepared by slurry packing and reported equivalent or better column efficiency. Ghijs and Sandra (A65) evaluated a number of polymer-coated HPLC supports packed in 320 µm i.d. fused-silica capillaries. Yan and co-workers (A66) demonstrated use of a commercial 320-µm-i.d. column in an electroosmotically pumped HPLC separation. Rusek and coworkers (A67) demonstrated a microcolumn LC coupled to gas chromatography, with an interface that allows pneumatic regulation of the LC column flow. Rebscher and Pyell (A68) described a method for determining contributions to band broadening in electrochromatography with packed microcolumns (100 µm i.d.). Steenackers and Sandra (A69) described the use of 50 µm i.d. open tubular capillaries for the LC of polar solutes and discussed the advantages over packed columns. Li and co-workers (A70) described the preparation of 10-320-µm-i.d. fused-silica capillaries in which a continuous-bed porous cation-exchange polymer has been formed. They discussed the advantages of these for LC/ MS experiments and demonstrated the performance of these
columns for protein separations. Cortes and Nicholson (A71) packed 100-500-µm-i.d. fused-silica capillaries with Chiracel OD and demonstrated the use of these for optical isomer separations. They demonstrated significantly better performance of this packing in their capillaries than in conventional 4.6-mm-i.d. columns and attributed this to a more efficient packing process. They note the very small amount of expensive stereoselective packing material required to prepare these microcolumns. Swart and coworkers (A72-A74) prepared and evaluated polyacrylate-coated fused-silica capillaries (5-11-µm i.d.) with phase ratios on the order of unity, thus producing open tubular columns with relatively high mass loadability. They applied on-column ultraviolet (UV) detection and reported these columns to be stable with mobilephase pH up to 12. They also demonstrated the use of these for separation of derivatized amino and aliphatic acids with on-column laser-induced fluorescence detection. Other Articles of Interest. Deinhammer and co-workers (A75) described a column containing nonporous glassy carbon spheres, in which they were able to modulate the colume selectivity electrochemically. Deinhammer and co-workers (A76) also reported an electrochemically modifiable stationary phase based on polypyrrole bonded to glassy carbon spheres. Inagaki and co-workers (A77) described a new packing method for capillary HPLC columns, using electrophoretic migration of ODSderivatized silica particles. Sentell (A78) presented a review (with 89 references) of the use of NMR and ESR for study of HPLC stationary phases. Rutan and Harris (A79) presented a review (with 54 references) of the use of electronic spectra to characterize HPLC stationary phases. Sentell and co-workers (A80) studied stationary phases with both 13C and 2H NMR, using the latter in a study of the solvation of reversed-phase stationary phases by perdeuterated mobile-phase components. Hansen and Harris (A81) measured the lateral diffusion of fluorescent probe molecules partitioned into C18 stationary phases. Kitagawa and Tsuda (A82) described the use of electrostatic fields to pack underivatized 10-µm-diameter silica particles in capillary columns. They reported that, with an applied field of 10 kV, a capillary column 11.5 cm in length packed in 4 min and produced a column with an HETP of 45 µm. Baumeister and co-workers (A83) determined the apparent transverse and axial dispersion coefficient of water in a chromatographic column by pulsed-field gradient NMR. They describe the approach as potentially useful in studying the structure and homogeneity of packings in preparative scale columns. Vissers and co-workers (A84) related the coagulating properties of slurry suspensions, the type of packing liquids, and the final performance of slurry-packed HPLC columns. Tallarek and co-workers (A85) applied NMR imaging to the chromatographic process, monitoring the migration of gadolimium chelates. By this means, they reported the first documented observation of formation and resorption of fissured and compacted zones in a column. Further reports of related work by this group may be found in the article by Bayer and co-workers (A86). Welinder and co-workers (A87) discussed the general problem with stationary-phase reproducibility from column to column and the effect this has on the HPLC of protein pharmaceuticals. INSTRUMENTATION Hyphenated Instrumentation. Barth (B1) reviewed recent developments in the use of hyphenated separation techniques for polymer analysis. Vreuls and co-workers (B2) presented a review Analytical Chemistry, Vol. 68, No. 12, June 15, 1996
589R
of equipment for and applications of LC coupled on-line with gas chromatography (GC). Grob (B3) reviewed development of transfer techniques for on-line LC/capillary GC. Cortes and coworkers (B4) developed an LC-supercritical fluid chromatograph with an interface between the two separations permitting large sample volume transfers between the two separation techniques. Senorans and co-workers (B5) discussed the use of a programmed temperature injector as the interface for an LC/GC instrument with reversed-phase LC separations. Blomberg and co-workers (B6) described a system coupling size-exclusion LC to gas chromatography. This system was demonstrated for determination of additives in a polymer matrix. Van Asten and co-workers (B7) discussed a size-exclusion LC-thermal field flow fractionation system for determining compositional heterogeniety in polydisperse polymer samples. Yoo and co-workers (B8) used temperature programming as an alternative to solvent programming on an LC/mass spectrometry instrument, using programming rates of 0.1-0.5 °C/min. Kassel and co-workers (B9) described a twodimensional microcolumn LC (microaffinity to reversed phase) system coupled to electrospray ionization MS, demonstrating the feasibility of this approach for biomolecule analysis. Holland and Jorgenson (B10) described a comprehensive two-dimensional microcolumn LC system for analysis of nanoliter volumes of biological samples. This system consisted of a 90 cm × 100 µm i.d. anion-exchange column coupled to a 3 cm × 100 µm i.d. reversed-phase column via an eight-port valve, with detection via laser-induced fluorescence. Among the applications shown is analysis of a single bovine chromaffin cell. LC-on-a-Chip. Emmer and co-workers (B11) reported fabrication and characterization of a silicon microvalve for gas or liquid chromatography. Manz and co-workers (B12) reported the development of a separation column system on a silicon microchip, demonstrating the device with a capillary electrophoresis separation. Jacobson and co-workers (B13) reported open channel electrochromatography on a glass microchip. They produced a 5.6 × 66 µm channel by standard photolithography and etching and then bonded octadecylsilane to the channel, producing an open tubular reversed-phase LC column. Sample injection and pumping were performed via electroosmosis, with fluorescence detection. Sample Preparation. On-line dialysis was reviewed by van de Merbel and Brinkman (B14) as a means of sample preparation for LC. Rodier and Birks (B15) described a dual-injector solvent focusing and elution technique developed to improve the efficiency of on-line analysis of C18 solid-phase extraction cartridges. Other Methods. Bowman and co-workers (B16) compared two commercially available software packages for LC solvent optimization. Readers interested in practical experience with such software may find value in the authors’ discussions of their experience. Boughtflower and co-workers (B17) discussed considerations in packing columns and choosing mobile phases for capillary electrochromatography. Coufal and co-workers (B18) discussed the reproducibility of electrochromatography on their home-constructed instrument. Crego and co-workers (B19) studied two different injection systems for open tubular column LC, a split injection system and a pressure pulse-driven stoppedflow injector. They compared the band broadening and sample injection volume reproducibility observed with 5-µm-i.d. columns. In this comparison, they found better band shape and reproducibility with the stopped-flow injector. Shoikhet and Engelhardt 590R
Analytical Chemistry, Vol. 68, No. 12, June 15, 1996
(B20) described a photometric flow measurement method, based on the photoconversion of malachite green leucocyanide, for characterization of flow rate stability and pulsation in LC or flow injection analysis pumps. Berloni and co-workers (B21) described a split-flow microgradient system for capillary LC separations, which was demonstrated on an LC/particle beam MS system. ELEMENTAL DETECTORS Reviews. Vela and Caruso (C1) reviewed LC and SFC with inductively coupled plasma (ICP)MS detection for trace metal speciation. Shepard and Caruso (C2) reviewed ICP-MS with some attention to applications in chromatography detection. Seubert (C3) reviewed the status of ICPMS as a chromatographic detector, including discussions of use of these instrumental systems for matrix elimination, for reduction of spectral interferences, and as a tool for metal speciation analysis. Culp and Ng (C4) reviewed analytical microwave-induced plasmas, with some focus on use of these in LC detection. Long and co-workers (C5) reviewed the development of microwave-induced plasmas for element-specific detection in chromatography. Flames. Weber and Berndt (C6) described a system to couple LC to flame atomic absorption for trace metal speciation. Wichems and Jones (C7) described a simple interface for directcoupling LC to a flame nebulizer for atomic emission or absorption detection. Inductively Coupled Plasma. Allen and Koropchak (C8) discussed the effects of extracolumn aerosol- and liquid-phase volumes on LC separations with ICP detection, demonstrating that extracolumn aerosol volume in laminar flow systems has a minor effect on peak broadening. Gotz and co-workers (C9) constructed an electrospray interface for ICP atomic emission as a means to interface to microcolumn LC. They found the mass limits of detection to be lower than those obtained with thermospray or pneumatic nebulizers, although the relatively low liquid flow rates in the electrospray detector result in poorer concentration detection limits. Peak broadening was a problem and was only acceptable with packed columns of 1-mm i.d. or larger. Heumann and co-workers (C10) discussed elemental speciation with an LC/ ICP-isotope dilution MS system. Bendicho (C11) evaluated an automated thermospray interface for coupling electrothermal atomization atomic absorption (AA) spectrometry to LC. This system employed periodic deposition of the LC column effluent on a graphite tube followed by a drying, atomization, and cooling cycle for the tube, yielding an AA signal every 40 s. Microwave-Induced Plasma. Wu and co-workers (C12) described a new spray chamber for flow injection analysis coupled to a microwave-induced plasma (MIP) based on a microwave plasma torch. This system was relatively tolerant of organic solvents and suggests the possible use of this interface for elemental detection in LC. Mason and co-workers (C13) employed a moving band system to couple LC to MIP atomic emission detection and demonstrated the device with detection of chlorine in chlorinated organic species. UV/VISIBLE IR, AND RAMAN DETECTORS UV/Visible. Svensson and Markides (D1) described a detector based on 200-µm optical fibers connected via a machined block to fused-silica capillary columns of the same outside diameter. This was applied to high-temperature (150 °C) open tubular column LC. Rinke and Hartig (D2) developed a UV
photometer based on a luminous crystal irradiated by a radioactive source, yielding a low-intensity, but stable UV light source with an estimated 10-year lifetime. Detection of light is based on a silicon photodiode. Noise in this system is ∼10 µAU. Synovec and co-workers (D3) devised a fiber-optic-based refractive index detector with an unjacketed fiber inserted into a transparent capillary. Infrared. Yang and Griffiths (D4) described an HPLC/FTIR system with a concentric flow nebulizer interfaced to a commercial direct-deposit GC/FT-IR interface. With this system, they report a minimum identifiable quantity of 10 ng for a typical nonvolatile polar organic molecule. Somsen and co-workers (D5) described a reversed-phase HPLC/FT-IR detector system with online extraction and solvent elimination. They compared this device to a direct-deposit FT-IR detection system. Raman. Howdle and Best (D6) described a microscale Raman flow cell for use with capillary HPLC columns. Cabalin and co-workers (D7) described a surface-enhanced Raman detector with a windowless flow cell, using colloidal silver as an active substrate. FLUORESCENCE DETECTORS The area of fluorescence detection has been a busy one, driven by the common needs for increased detection sensitivity in conventional LC, capillary LC, and capillary electrophoresis. Shear and co-workers (E1) discussed the optimization of fluorescence detector sensitivity in separations where analyte bands move at different velocities, requiring attention to digitization rates and changes in excitation source intensity during the course of pherogram or chromatogram development. While this article focuses on electrophoresis, the principles are applicable to oncolumn LC detection as well. A comparison of UV laser-induced and conventionally excited fluorescence detection was done by van de Nesse and co-workers (E2). Smalley and co-workers (E3) performed LC detection with a multiharmonic FT phase modulation spectrofluorometer. This detection system allows simultaneous measurement of solute fluorescence intensity signals and fluorescence lifetimes on-the-fly, adding another simultaneous dimension of data. Takeuchi and Miwa reported enhancement of fluorescence intensity signals with cyclodextrin added to the mobile phase (E4) and with a cyclodextrin bonded phase in the detection cell (E5). Oosterkamp and co-workers (E6) used affinity proteins, such as antibodies or avidin, labeled with fluorescent groups in a postcolumn reaction scheme to detect ligands. The method of removing excess labeled protein is discussed. The authors report a detection limit for biotin of 160 fmol in this instrument. The relationship between concentration of the affinity protein, reaction time, and sensitivity are discussed. Fluorescence line-narrowing spectroscopy was used as an off-line identification and quantitation method for substituted pyrenes by van de Nesse and co-workers (E7), in which the effluent from a narrow-bore LC column was deposited on a TLC plate. Abbas and Shelly (E8) studied the optical properties of axially illuminated flow cells for microcolumn LC for simultaneous absorbance and fluorescence detection. Gooijer and co-workers (E9) reviewed recent work in laser-induced luminescence detection for LC and electrophoresis. Smalley and McGown (E10) evaluated limits of detection and resolution for on-the-fly fluorescence lifetime measurements. Takeuchi and Miwa (E11) demonstrated fluorescence intensity enhancements for dansyl amino acids when bovine serum albumin
was added to the mobile phase. Mank and co-workers (E12) compared various lasers (HeNe, diode, argon ion) as excitation sources for near-IR fluorescence detection of disulfonated aluminum phthalocyanine. They found the diode laser to be the best choice in this application, due to its low cost and limits of detection comparable to the argon ion laser. These authors (E13) also reported work with pulsed lasers (XeCl excimer/dye and Nd: YAG/dye systems) and reported approximately 20-200 times poorer limits of detection with these lasers than with the diode laser. van de Nesse and co-workers (E14) studied the applicability of two-photon fluorescence to conventional column LC. Karnes and co-workers (E15) reported on a variety of derivatization agents for use with diode lasers. van de Nesse and co-workers (E16) reviewed considerations for use of lasers for fluorescence excitation sources in LC. Johnston (E17) presented a study of the effect of baseline offsets on the measurement of excited-state lifetimes from HPLC fluorescence signals, This study shows how a baseline offset equal to 1% of the peak height can lead to a 60% error in the measured lifetime. He discusses methods for correcting data for these offsets. Takeuchi and Miwa (E18, E19) demonstrated enhanced fluorescence detection limits for dansylated amino acids, when the detection cell was packed with the LC column stationary phase. Mank and Yeung (E20) built a simple diode laser-induced fluorescence detector for capillary electrophoresis and synthesized a dicarbocyanine fluorophore with a succinimidyl ester functionality for derivatization of amines. They found a detection limit of 0.1 amol of derivatized glycine with this instrument. Kuklenyik and Patonay (E21) described development and evaluation of a photodiode-based fluorescence detector, using cyanine dyes fluorescing in the near-IR. CHEMILUMINESENCE DETECTORS Niederlaender and co-workers (F1) developed a luminol chemiluminescence detector based on on-line photochemical production of organic hydroperoxides. Walters and co-workers (F2) compared chemiluminescence to fluorescence detection for analysis of fluoresceamine derivatives of histamine. In this particular case, they demonstrated ∼100-fold higher sensitivity for fluorescence detection. Niederlaender and co-workers (F3) described in-depth studies of a chemiluminescence detection system with photoinduced production of singlet oxygen (which has been described in earlier publication). They compared this device to a commercially available reagent for singlet oxygen generation and to a newly constructed photochemical reactor, with these systems applied to the detection of polychlorinated biphenyls. Ryerson and co-workers (F4) described a gas-phase chemiluminescence detector for sulfur-containing compounds in liquid matrices, compatible with input liquid flow rates of 0.4-9.9 mL min-1. They demonstrated this detector with reversed-phase LC separations of pesticides, proteins, and blood thiols. Gilman and co-workers (F5) reported electrogenerated chemiluminescence detection for capillary electrophoresis, based on the luminolhydrogen peroxide reaction, reporting detection limits for alkylamines on the order of 1 fmol. MASS SPECTROMETRY DETECTORS Perhaps the biggest news in this particluar area is the degree to which LC/MS has been reduced to routine practice by the availability of reliable commercial interfaces. Only those who remember the “early years” of work in this field can fully appreciate the progress represented in the article by Pullen and Analytical Chemistry, Vol. 68, No. 12, June 15, 1996
591R
Richards (G1), in which they describe an automated LC/MS system at their facility. This system provides “walk-up” LC/MS service for synthetic chemists and does not routinely involve a mass spectroscopist. Reviews. Creaser and Stygall (G2) reviewed instrumentation and applications for particle beam LC/MS. Garcia and Barcelo (G3) published an overview of LC/MS with discussions of the advantages and limitations of different interfacing systems and selected applications. Voyksner (G4) reviewed atmospheric pressure ionization LC/MS, with particular attention to environmental applications. Bruins (G5) reviewed instrumentation and ionization techniques for atmospheric pressure ionization MS, with discussions of interfacing to LC and capillary electrophoresis. Caprioli (G6) reviewed LC and capillary electrophoresis with MS detection with examples in biomolecule applications. The reader is advised that this publication, issued in 1994, is the published proceedings of a 1992 meeting. Stroh and Rinehart (G7) reviewed LC/fast-atom bombardment MS. Linscheid and Westmoreland (G8) reviewed the application of LC/MS to trace organic compound analysis. Niessen and Tinke (G9) reviewed principles and developments in LC/MS, with particular attention to electrospray ionization, atmospheric pressure ionization, and particle beam systems. Carey and co-workers (G10) reviewed methods, LC being among them, for sample introduction to plasma mass spectrometry. Bruins (G11) reviewed LC/atomospheric pressure ionization MS applications in pharmacy, biochemistry, and general chemistry. Cappiello and Famiglini (G12) evaluated a modified HewlettPackard LC/MS particle beam interface allowing eluent flow rates of 1 µL min-1. And they (G13) modified a particle beam LC/MS interface, improving its performance for thermally unstable phenoxy herbicide molecules. Bellar and Budde (G14) studied the effect of a dc glow discharge on the performance of a particle beam LC/MS interface. They found an increase in signal intensity of 2-6 for 12 test compounds. Wilkes and co-workers (G15) studied the particle beam interface and concluded that particle size distribution was not the major factor limiting the reproducibility of analyte transmission efficiency. He and co-workers (G16) studied chemical reduction of compounds containing nitro and sulfoxide groups in a particle beam LC/MS system. They observed significant influence on this process from changes in LC flow rate and desolvation chamber temperature, but little effect from changes in ion source temperature. Huang and Garza (G17) optimized a commercial particle beam interface by statistical experimental design. Caimi and Brenna (G18) used a moving wire to interface a liquid chromatograph to MS for purposes of combustion carbon isotope ratio measurements. Purser (G19) described an instrumentation study aimed at producing a miniature accelerator MS for use with LC and GC for tracking and metabolism studies with 14C-labeled molecules. Tomlinson and co-workers (G20) discussed inductively coupled plasma MS as an ultratrace elemental detector for LC, CE, and SFC. Roboz and co-workers (G21) employed a microvalve between a capillary LC column and the MS detector to allow diversion of nonvolatile sample buffer salts in protein solutions, as an alternative to preinjection sample preparation. Eshraghi and Chowdhury (G22) discussed the effect of trifluoroacteic acid-containing mobile phases on LC/electrospray 592R
Analytical Chemistry, Vol. 68, No. 12, June 15, 1996
ionization MS. They describe means for modification of the spray tip to improve reliability. Hopfgartner and co-workers (G23) discussed the concentration-sensitive characteristics of pneumatically assisted electrospray ionization MS as an LC detector. Reiser and Fogiel (G24) provided an experimental comparison and discussion of electrospray and fast-atom bombardment (FAB) ionization applied to LC/MS detection of small polar molecules. Emmett and Caprioli (G25) described a microelectrospray ionization source developed to increase sensitivity compared to conventional electrospray. They demonstrate detection of 1 femtomole of methionine-enkephalin. Chen and co-workers (G26) evaluated electrospray ion mobility spectrometry as a detector for microbore LC. Wilkes and co-workers (G27) inserted an ac corona-discharge device upstream of a thermspray vaporizer tip to neutralize aerosol static charging. This provided some increased signal intensity in the absence of ammonium acetate in the LC mobile phase but none if this salt was present. Murray and co-workers (G28) reported the application of aerosol MALDI to LC/MS. Wang and co-workers (G29) interfaced LC with time of flight MS (TOFMS) via a pulsed sample introduction interface. This system was compatible with LC eluent flow rates of 0.5-1.6 mL min-1, with ∼0.5% of the LC eluent pulsed into the MS system. Asakawa and co-workers (G30) devised a means of postcolumn addition of the matrix for FABMS, allowing independent selection of more nearly optimal LC mobile phases and FAB matrix solutions. Gordon and co-workers (G31) coupled electroosmotic pumping, a packed capillary LC column, and MS detection with continuous-flow FAB. Tinke and co-workers (G32) constructed a hyperthermal surface ionization interface for LC/MS. This system was compatible with LC eluent flow rates of 0.1-10 µL min-1. They demonstrate detection limits for polycyclic aromatic hydrocarbons below 200 pg. Carazzato and Bertrand (G33) characterized a glow-discharge ion source for LC/MS. Other Articles. Qian and Lubman (G34) evaluated an LC/ MS detection system based on a reflectron TOFMS system with an ion trap front end. The ion trap was used for ion storage with periodic ion injection into the reflectron TOFMS system. This sytem converted the continuous electrospray inlet system into a pulsed inlet system suitable for the analysis by TOFMS. This system was applied to a 20-pmol tryptic digest analysis. Debets and co-workers (G35) described an LC/MS system in which the LC column eluate is passed through a self-regenerating ionexchange suppressor, which they used to remove phosphate buffers prior to introduction of the eluate to the MS. They demonstrated this interface with an eluent containing 10 mM ammonium phosphate. Jones and co-workers (G36) reported on interlaboratory validation studies of LC/MS methods to determine realistic expectations for precision and accuracy. Jones and coworkers (G37) discussed results of three interlaboratory studies of LC/MS methods for environmental analytes. ELECTROCHEMICAL DETECTORS Ewing and co-workers (H1) reviewed electrochemical detectors for microcolumn separations, including LC and capillary electrophoresis. Warner (H2) reviewed representative amperometric, coulometric, conductometric, and potentiometric LC detectors. Microelectrodes and Microcolumns. Niwa and co-workers (H3) obtained improved detection limits in their catecholamine
LC application with a carbon interdigitated array microelectrode. Tudos and co-workers (H4) developed an electrochemical detector cell for open tubular capillary LC and capillary electrophoresis, consisting of a carbon fiber bundle working electrode and a tubular Ag/AgCl reference. Effective cell volume was 1 nL and detection limits for analytes in their applications were ∼1 fmol. Ruban (H5) presented an amperometric detector with cylindrical working electrode with 60-nL cell volume for capillary LC and detection limits for nitrophenols on the order of 100 fg. Bohs and co-workers (H6) described the “UniJet”, an electrochemical detector cell made for direct attachment to the outlet end of columns of 1-mm i.d. or less and flow rates of 0.1-200 µL min-1. Siddiqui and Shelly (H7) described a microelectrode for 250-µmi.d. packed fused-silica capillary column LC detection. This electrode is described as an amperometric/potentiometric detector. Detection limits for phenols are at the femtomole level. Amperometry. Just and co-workers (H8) described the design and properties of three amperometric LC detectors with mercury working electrodes. Kawaguchi and co-workers (H9) examined the effect of ionic surfactants on the amperometric response of an electrochemical detector based on a gold electrode modified with an alkanethiol self-assembled monolayer. Cationic and anionic surfactants were detectable with this device. Ortiz and co-workers (H10) modified glassy carbon electrodes with an electropolymerized film to protect the carbon surface from poisoning. The electode was evaluated in an LC detector for phenolic materials. Stitz and Buchberger (H11) studied a variety of electrode materials, including Ni, Cu, and Co metal and metalmodified glassy carbon, for oxidative amperometric detection of alcohols, polyols, and carbohydrates. They offered comparisons of stability and sensitivity. van Riel and Olieman (H12) developed an electrochemical detector for tryptophan, tyrosine, and sulfurcontaining peptides based on a two-step potential waveform and a platinum wall-jet electrode. Detection limits are in the picomole range. Casella and Marchese (H13) studied a platimun-based, chemically modified glassy carbon electrode for detection of sulfite ion in ion-exclusion chromatography. Detection limits were on the order of 1 ppb. Casella (H14) studied a similar electrode as an amperometric LC or flow injection detector for alcohols in acidic media, with a detection limit of 1 ppm for aliphatic alcohols. Vandenberg and Johnson (H15)compared pulsed amperometric and integrated voltammetric LC detection for organic sulfur compounds. Carbohydrate Detection. Marioli and co-workers (H16) applied a nickel-chromium alloy electrode to the detection of carbohydrates in anion-exchange LC. Cyclic voltammetry (CV) with this electrode was compared to that obtained with pure nickel electrodes. The limit of detection for glucose is ∼500 fmol. Luo and Kuwana (H17) developed a nickel-titanium alloy electrode for carbohydrate detection. While CV experiments show that titanium does not participate in the carbohydrate oxidation, its presence in the alloy improves the reproducibility and lifetime of the electrode compared to pure nickel. Roberts and Johnson (H18) studied the frequency-dependent response of gold electrodes for the detection of carbohydrates. Other Articles. Roush and Anderson (H19) demonstrated the application of square-wave voltammetry to gradient elution LC. In tests on quinones and phenolics, detection limits were on the order of 10 pg. Slater and Watt (H20) described a rapidscanning electrochemical detector with microelectrode. Isildak
and Covington (H21) demonstrated tubular PVC membrane potentiometric electrodes as detectors in nonsuppressed ion chromatography. Macher (H22) used postcolumn photolysis followed by electrochemical detection for LC detection, at the picogram level, of drugs containing aromatic chlorines and thiazide functional groups. NMR DETECTORS Albert (I1) reviewed the use of NMR detection in separation chemistry. Stevenson and Dorn (I2) described 13C dynamic nuclear polarization as an HPLC detection scheme. The paper demonstrates separation and detection of halogenated organic species. Wu and co-workers (I3-I5) reported development of nanoliter-volume flow cells applied to on-line NMR detection in capillary electrophoresis and microcolumn LC. This work demonstrated 5-200-nL detector cell volumes, NMR line widths less than 10 Hz, and detection limits of 50 ng for amino acids with static mode detection. Reports of further developments by this group were in press as of the end of this review period and interested readers are advised to look in the journal Science for more recent information. Pullen and co-workers (I6) described an LC system combining NMR and mass spectrometry detection and demonstrated the application of this system to structural determinations in triazoles. OTHER DETECTORS Thermooptical Detectors. Saz and Diez-Masa (J1) reviewed thermooptical spectroscopy as a detection technique for open tubular capillary LC and electrophoresis separations. Snook and Lowe (J2) reviewed thermal lens spectrometry, including its use in liquid-phase separation systems. Rosenzweig and Yeung (J3) described a laser-based double-beam thermal lens detector for microcolumn LC, with 100-fold better detection limits than commercial absorption detectors. Sanchis Mallols and co-workers (J4) discussed concentration gradient perturbations with thermal lens detection in micellar LC separations and their impact on detector sensitivity and noise. Tran and co-workers (J5) developed an infrared thermal lens detector and demonstrated its use for both direct and indirect detection. This system used a solid-state tunable F-center exciting laser and a collinear He-Ne monitoring laser to detect picogram amounts of phenol and chlorophenols. Faubel and co-workers (J6) discussed a number of detection techniques, including photoacoustic spectroscopy, photothermal deflection, thermal lensing, and photothermal phase shift spectroscopy for LC detection. Optical Activity Detectors. Rosenzweig and Yeung (J7) described a double-beam circular dichroism (CD) detector with electronic noise cancellation. They demonstrated a detection limit of 25 ng for a tris(ethylenediamine)cobalt(III) complex, nearly as sensitive as thermal lens detection and ∼1000× more sensitive than conventional CD spectrometers. Nunes and co-workers (J8) discussed biomedical applications of four-wave mixing as a detection technique for capillary column separations and CD measurements. Tran and co-workers (J9) described a novel vibrational circular dichroism LC detector based on measurement of CD in the infrared. The instrument consisted of a solid-state spectral tunable F-center laser light source (2.4-3.5 µm), mechanical chopper, photoelastic modulator, and liquid nitrogencooled indium antimonide detector. As configured, this instrument was capable of detecting micrograms of molecules with OH Analytical Chemistry, Vol. 68, No. 12, June 15, 1996
593R
groups. Hayakawa and co-workers (J10) presented theoretical considerations for optimizing operation of a polarized photometric detector they developed earlier. Yamamoto and co-workers (J11) described a new split-flow cell polarized spectrophotometric detector. Dappen and co-workers (J12) discussed quantitative measurements with polarimetric detectors. They discussed both precision and accuracy in these detectors, including measurement artifacts caused by refractive index effects. Surface Plasmon Resonance. Cepria and co-workers (J13, J14) described a test of a surface plasmon resonance sensor for use as an LC detector and compared this device to a refractive index detecor for carbohydrate separations. Light Scattering Detectors. Lewis and co-workers (J15) developed a new LC detector for macromolecules of >10 000 molecular weight based on electrospray atomization and a condensation particle counter. Detection limits for some test proteins were on the order of 0.1-1 ppm. This detector is suitable for capillary column separation flow rates. Allen and co-workers (J16) interfaced a condensation nucleation light scattering detector to reversed-phase LC. They discuss means to deal with the noise contributions due to dissolved residues in organic solvents typically used for LC. Gas Chromatography Detectors in LC. Kientz and Brinkman (J17) reviewed the use of gas chromatography detectors in LC, specifically thermionic, flame photometric, and electron capture. Conte and Barry (J18) evaluated an aerosol alkali flame ionization detector for LC, with a heated interface for solvent evaporation. Bernard and co-workers (J19) designed and characterized a total-consumption flame photometric detector for sulfur- and phosphorus-containing compound detection. Howard and co-workers (J20) discussed optimization of a microcolumn flame sulfur chemiluminescence detector. Zegers and co-workers (J21) coupled a photoionization detector to packed capillary liquid and supercritical fluid chromatographs. They demonstrated this device with organic acids and organosulfur/phorphorus compounds. Zegers and co-workers (J22) developed a new type of interface to couple electron capture to packed capillary LC and demonstrated the system for pesticides and chlorophenols. Other Detectors. Lima and co-workers (J23, J24) reported a dynamic surface tension detector. This device is based on measuring drop repetition rate at the end of a capillary and is sensitive to solutes that alter the surface tension, and thus the drop size and rate, of the eluent. Surfactants can be detected at the low-ppm level with this system. Gale and Li (J25) described a miniaturized capacitance detector. The potential for fabricating this device on a silicon chip along with a microcolumn is discussed. Emneus and Marko-Varga (J26) reviewed biospecific detection in LC, flow injection analysis, and capillary electrophoresis. Vanderlaan and co-workers (J27) described a perfusion immunoassay for acetylcholinesterase involving automated twodimensional LC with the second dimension being an immunoaffinity column. The second column trapped the enzyme upon elution from the first, after which enzyme substrate is pumped through the affinity column and the reaction products are detected at the outlet end. Krull and co-workers (J28) reviewed solid-phase derivatization reactions for biomedical liquid chromatography. Rubio and co-workers (J29) discussed on-line UV photolysis for determination of organoarsenic compounds. The photolyzed organoarsenics are converted to arsines and determined by emission or absorption atomic spectroscopy. Billedeau and co594R
Analytical Chemistry, Vol. 68, No. 12, June 15, 1996
workers (J30) interfaced a particle beam to a thermal energy analyzer (TEA, a commercial gas-phase chemiluminescence detector selective for N-nitroso compounds) and electron impact MS to detect nonvolatile N-nitrosamines, such as N-nitrosodiethanolamine, for which it had a detection limit of 5 ng. COMPUTATION Reviews. Bryant and co-workers (K1) reviewed expert systems for chromatography. The article presents a scheme for the classification of these systems and examines the reasons individual systems were created and their intended applications. The authors believe that there are relevant ideas in the knowledge engineering community that have not yet made their way into this application area. Diode-Array Detector Data Interpretation. Many computation-oriented articles focus on the interpretation of diode-array detector signals for determination of LC peak purity or improved quantitation in the presence of overlap. Poe and Rutan (K2) evaluated methods of quantitation involving both fluorescence and retention time data for diode-array fluorescence detection in situations with chromatographic component overlap, including the conventional peak area and peak height methods, as well as an adaptive Kalman filter and the generalized rank annihilation method. Gilliard and co-workers (K3) applied evolving factor analysis to peak purity monitoring. Tauler and Barcelo (K4) applied multivariate curve resolution techniques to quantitation of overlapping peaks. Vanslyke and Wentzell (K5) discussed the limitations of applying evolving principal component innovation analysis to peak purity determination. Schostack and Malinowski (K6) used window factor analysis for peak deconvolution. They compared the performance of this approach for quantitative analysis to rank annihilation factor and matrix regression analyses and found similar results. Keller and co-workers (K7) evaluated the performance of three chemometrics techniques for assessment of peak purity and found that they were able to detect less than 1% of a spectrally similar overlapping peak with all three techniques. Bakken and Kalivas (K8) evaluated condition index evolving profiles (CIEPs) and singular value evolving profiles for assessing peak purity. Cuesta-Sanchez and co-workers (K9) applied SIMPLISMA to similar measurements and compared its performance to Gram-Schimdt orthogonalization. These authors (K10) also examined the effect of a variety of different preprocessing methods for principal component analysis. Sanchez and coworkers (K11, K12) evaluated three modified Gram-Schmidt orthogonalization techniques for peak purity measurement, using both simulated and experimental chromatograms. Elbergali and co-workers (K13) performed a number of simulations to study the effect of noise, peak position, and spectral similarities on the ability to resolve overlapping peaks with evolutionary factor analysis. Wentzell and co-workers (K14) discussed the use of Kalman filters for peak purity analysis, using a new method that compensates for some detector system nonideal behavior, such as nonlinear response and heteroscedastic noise. Tauler (K15) discussed multivariate curve resolution applied to two-dimensional data sets in LC. Fabre and co-workers (K16) evaluated nine different techniques for peak purity determination in experimental data and rank-ordered the techniques on the basis of their sensitivity to a coeluting peak. Column Selection. Lockmuller and co-workers (K17) described a means of predicting component retention across a series
of LC columns with similar bonded phases (e.g., C18) by factor analytical modeling. Stauffer and Dessy (K18) described a system for selecting columns for chiral molecule separations, named CHIRULE. This system constructs an n-dimensional information space from a large number of known chiral separations, where the molecular fragments attached to the chiral center each comprise separate dimensions. A new target molecule is added to this information space, and the space is searched for other molecules with similar fragment properties to recommend columns most likely to separate the new target enantiomers. Olsen and Sullivan (K19) characterized 17 commercial C18 columns with chromatographic test mixtures and then used principal component and cluster analysis to categorize the columns into groups with similar properties. They evaluated this categorization scheme by comparing the performance of these columns in separating mixtures of pharmaceutical compounds. Other Papers. Josefson and co-workers (K20) presented a detector linearity test procedure involving principal component analysis requiring only one injection of a single sample. This method can determine linearity across the detector range spanned by the largest fully resolved peak in the test chromatogram. Bahowick and co-workers (K21) described the analysis of unresolved chromatograms by the absorbance ratio and sequential chromatogram ratio methods to facilitate analysis of a peak overlapped with two others. ACKNOWLEDGMENT
The author gratefully acknowledges H. J. Cortes for review and comment on the manuscript. L. David Rothman is an Associate Scientist in the Analytical Sciences Laboratories of The Dow Chemical Co. He received a B.S. in chemistry from Principia College, Elsah, IL, and a Ph.D. in analytical chemistry from Michigan State University. He joined The Dow Chemical Co. in 1976 and has worked mainly in the areas of separations science and scientific computing He is a member of the American Chemical Society, Analytical Division. In 1993, he chaired the Gordon Research Conference on Analytical Chemistry. His current work includes consultation, general problem solving, and analytical method development for discovery and process development research in synthetic and fermentation-derived agricultural chemicals.
LITERATURE CITED COLUMNS (A1) Ratanathanawongs, S. K.; Giddings, J. C. Chromatographia 1994, 38, 545-54. (A2) Pazourek, J.; Urbankova, E.; Chmelik, J. J. Chromatogr., A 1994, 660, 113-8. (A3) Kaneko, S.; Mitsuzawa, T.; Ohmori, S.; Nakamura, M.; Nobuhara,; K.; Masatani, M. J. Chromatogr., A 1994, 669, 1-7. (A4) Kaneko, S.; Mitsuzawa, T.; Ohmori, S.; Nakamura, M.; Nobuhara, K.; Masatani, M. Chem. Lett. 1993, (8), 1275-8. (A5) Loere, A.; Szasz, Gy.; Budvari-Barany, Zs. J. Liq. Chromatogr. 1995, 18, 287-95. (A6) Sun, L.; Annen, M. J.; Lorenzano-Porras, F.; Carr, P. W.; McCormick, A. V. J. Colloid Interface Sci. 1994, 163, 46473. (A7) Lorenzano-Porras, C. F.; Annen, M. J.; Flickinger, M. C.; Carr, P. W.; McCormick, A. V. J. Colloid Interface Sci. 1995, 170(2), 299-307. (A8) Weber, T. P.; Jackson, P. T.; Carr, P. W. Anal. Chem. 1995, 67, 3042-50. (A9) Akama, Y.; Kanno, H. Anal. Chim. Acta 1995, 309, 153-6. (A10) Nagaoka, S.; Ihara, H.; Honbo, J.; Hirayama, C.; Kurisaki, H.; Ikegami, S. Anal. Sci. 1994, 10, 543-51. (A11) Hirayama, C.; Nagaoka, S.; Matsumoto, T.;Ihara, H.; Honbo, J.; Kurisaki, H.; Ikegami, S. J. Liq. Chromatogr. 1995, 18, 1509-20. (A12) Serys, A. s; Liesiene, J.; Urbonaviciene, J.; Maruska, A.; Radzevicius, K.; Valatkeviciute, D.; Bumelis, V. J. Liq. Chromatogr. 1994, 17, 749-60. (A13) Inoue, S.; Ohtaki, N. J. Chromatogr. 1993, 645, 57-65. (A14) Petro, M.; Berek, D.; Novak, I. React. Polym. 1994, 23, 17382. (A15) Honda, F.; Honda, H.; Koishi, M. J. Chromatogr. 1995, 696, 19-30.
(A16) Pesek, J. J.; Tang, V. H. Chromatographia 1994, 39, 649-54. (A17) Pesek, J. J.; Williamsen, E. J. J. Chromatogr. Libr. 1995, 57, 371-401. (A18) Williams, K. L.; Stalcup, A. M. Molecular Interactions in Bioseparations; Ngo, T. T., Ed.; Plenum: New York, 1993; pp 189-202. (A19) Allenmark, S.; Andersson, S. Molecular Interactions in Bioseparations; Ngo, T. T., Ed.; Plenum: New York, 1993; pp 17987. (A20) Kirkland, J. J.; Henderson, J. W. J. Chromatogr. Sci. 1994, 32, 473-80. (A21) Bolck, A.; Smilde, A. K.; Bruins, C. H. P.; Coenegracht, P. M. J.; Doornbos, D. A., InCINC’94-First Int. Chemom. InterNet Conf., http://www.emsl.pnl.gov:2080/docs/incinc/chromat/ ABdoc.html. (A22) Montes, M. C.; van Amen, C.; Pesek, J. J.; Sandoval, J. E. J. Chromatogr. 1994, A, 688, 31-45. (A23) Moriyama, H.; Anegayama, M.; Komiya, K.; Kato, Y. J. Chromatogr., A 1995, 691, 81-9. (A24) Schmid, J.; Albert, K.; Bayer, E. J. Chromatogr., A 1995, 694, 333-45. (A25) Pesek, J. J.; Matyska, M. T. J. Chromatogr., A 1994, 687(1), 33-44. (A26) Jinno, K.; Nakamura, H. Chromatographia 1994, 39, 285-93. (A27) Buszewski, B.; Gilpin, R. K.; Jaroniec, M. Chem. Anal. (Warsaw) 1994, 39, 673-9. (A28) Stalling, D. L.; Guo, C. Y.; Saim, S. J. Chromatogr. Sci. 1993, 31, 265-78. (A29) Wongyai, S. Chromatographia 1994, 38, 485-90. (A30) Houbenova, A.; Claessens, H. A.; De Haan, J. W.; Cramers, C. A.; Stulik, K. J. Liq. Chromatogr. 1994, 17, 49-68. (A31) Friebe, S.; Gebauer, S.; Krauss, G. J.; Goermar, G.; Krueger, J. J. Chromatogr. Sci. 1995, 33, 281-4. (A32) Chriswanto, H.; Ge, H.; Wallace, G. G. Chromatographia 1993, 37, 423-8. (A33) Ge, H.; Gilmore, G.; Wallace, G. G. J. Liq. Chromatogr. 1994, 17, 1301-16. (A34) Akapo, S. O.; Simpson, C. F. J. Chromatogr. Sci. 1994, 32, 86-92. (A35) Thienpont, A.; Felix, G. Chromatographia 1993, 37, 505-10. (A36) Murayama, K.; Nakamura, H.; Nakajima, T.; Takahashi, K.; Yoshida, A. Anal. Sci. 1994, 10, 497-9. (A37) Murayama, K.; Nakamura, H.; Nakajima, T.; Takahashi, K.; Yoshida, A. Microchem. J. 1994, 49, 362-7. (A38) Sun, L.; Carr, P. W. Anal. Chem. 1995, 67, 2517-23. (A39) Da, S.; Yue, W.; Wen, Y.; Da, H.; Wang, Z. Anal. Chim. Acta 1994, 299, 239-47. (A40) Hanson, M.; Kurganov, A.; Unger, K. K.; Davankov, V. A. J. Chromatogr. 1993, 656, 369-80. (A41) Petro, M.; Berek, D. Chromatographia 1993, 37, 549-61. (A42) Kataev, A. D.; Saburov, V. V.; Reznikova, O. A.; Kapustin, D. V.; Zubov, V. P. J. Chromatogr., A 1994, 660, 131-6. (A43) Zuo, Y. M.; Zhu, B. R.; Liao, Y.; Gui, M. D.; Pang, Z. L.; Qi, J. X. Chromatographia 1994, 38, 756-60. (A44) Majors, R. E. LC-GC 1993, 11, 778. (A45) Nagaoka, S.; Ihara, H.; Hirayama, C. Polym. J. 1993, 25, 60918. (A46) Hosoya, K.; Kishii, Y.; Kimata, K.; Araki, T.; Tanaka, N. Chromatographia 1994, 38, 177-82. (A47) Smigol, V.; Svec, F.; Frechet, J. M. J. J. Liq. Chromatogr. 1994, 17(2), 259-76. (A48) Smigol, V.; Svec, F.; Frechet, J. M. J. Anal. Chem. 1994, 66, 2129-38. (A49) Ogawa, N.; Taguchi, H.; Sato, T. Chem. Pharm. Bull. 1993, 41, 2180-2. (A50) Sellergren, B. J. Chromatogr., A 1994, 673, 133-41. (A51) Hosoya, K.; Sawada, E.; Kimata, K.; Araki, T.; Tanaka, N. J. Chromatogr. 1994 662, 37-47. (A52) Smigol, V.; Svec, F.; Frechet, J. M. J. Anal. Chem. 1994, 66, 4308-15. (A53) Chen, Y.; Shieh, D. J. Polym. Res. 1994, 1, 115-22. (A54) Freitag, R.; Frey, D.; Horvath, C. J. Chromatogr., A 1994, 686, 165-77. (A55) Hosoya, K.; Kimata, K.; Araki, T.; Tanaka, N.; Frechet, J. M. J. Anal. Chem. 1995, 67, 1907-11. (A56) Wang, Q. C.; Svec, F.; Frechet, J. M. J. Anal. Chem. 1995, 67, 67. (A57) Svec, F.; Frechet, J. M. J. J. Chromatogr., A 1995, 702, 8995. (A58) Gawdzik, B.; Matynia, T. Chem. Anal. (Warsaw) 1995, 40(1), 103-9. (A59) Ogino, K.; Sato, H.; Aihara, Y.; Suzuki, H.; Moriguchi, S. J. Chromatogr., A 1995, 699, 67-72. (A60) Danielson, N. D.; Wangsa, J.; Shamsi, S. A. J. Liq. Chromatogr. 1995, 18, 2579-92. (A61) Cole, L. J.; Schultz, N. M.; Kennedy, R. T. J. Microcolumn Sep. 1993, 5, 433-9. (A62) St. Claire, R. L., III; Dohmeier, D. M.; Jorgenson, J. W. J. Microcolumn Sep. 1991, 3, 303-9. (A63) Goehlin, K.; Larsson, M. J. Microcolumn Sep. 1991, 3, 54756. (A64) Crescentini, G.; Mastrogiacomo, A. R. J. Microcolumn Sep. 1991, 3, 539-45. (A65) Ghijs, M.; Sandra, P. J. Microcolumn Sep. 1991, 3, 443-8. (A66) Yan, C.; Schaufelberger, D.; Erni, F. J. Chromatogr., A 1994, 670, 15-23.
Analytical Chemistry, Vol. 68, No. 12, June 15, 1996
595R
(A67) Rusek, M.; Cigankova, M.; Krejci, M.; Kahle, V. J. Microcolumn Sep. 1994, 6, 245-8. (A68) Rebscher, H.; Pyell, U. Chromatographia 1994, 38, 737-43. (A69) Steenackers, D., Sandra, P. J. High Resolut. Chromatogr. 1994, 17, 557-8. (A70) Li, Y.; Liao, J.; Nakazato, K.; Mohammad, J.; Terenius, L.; Hjerten, S. Anal. Biochem. 1994, 223, 153-8. (A71) Cortes, H. J.; Nicholson, L. W. J. Microcolumn Sep. 1994, 6, 257-62. (A72) Swart, R.; Kraak, J. C.; Poppe, H. J. Chromatogr., A 1994, 670, 25-38. (A73) Swart, R.; Kraak, J. C.; Poppe, H. Chromatographia 1995, 40, 587-93. (A74) Swart, R.; Kraak, J. C.; Poppe, H. J. Chromatogr., A 1995, 689, 177-87. (A75) Deinhammer, R. S.; Ting, E.; Porter, M. D. Anal. Chem. 1995, 67, 237-46. (A76) Deinhammer, R. S.; Porter, M. D.; Shimazu, K. J. Electroanal. Chem. 1995, 387, 35-46. (A77) Inagaki, M.; Kitagawa, S.; Tsuda, T. Kuromatogurafi 1993, 14, 55R-60R. (A78) Sentell, K. B. J. Chromatogr. 1993, 656, 231-63. (A79) Rutan, S. C.; Harris, J. M. J. Chromatogr. 1993, 656, 197215. (A80) Sentell, K. B.; Bliesner, D. M.; Shearer, S. T. Spec. Publ.-R. Soc. Chem. 1994, 139 (Chemically Modified Surfaces), 190202. (A81) Hansen, R. L.; Harris, J. M. Anal. Chem. 1995, 67, 492-8. (A82) Kitagawa, S.; Tsuda, T. Kuromatogurafi 1994, 15, 137-40. (A83) Baumeister, E.; Klose, U.; Albert, K.; Bayer, E.; Guiochon, G. J. Chromatogr., A 1995, 694, 321-31. (A84) Vissers, J. P. C.; Claessens, H. A.; Laven, J.; Cramers, C. A. Anal. Chem. 1995, 67, 2103-9. (A85) Tallarek, U.; Baumeister, E.; Albert, K.; Bayer, E.; Guiochon, G. J. Chromatogr., A 1995, 696, 1-18. (A86) Bayer, E.; Baumeister, E.; Tallarek, U.; Albert, K.; Guiochon, G. J. Chromatogr., A 1995, 704, 37-44. (A87) Welinder, B.; Kornfelt, T.; Sorensen, H. Anal. Chem. 1995, 67, 39A-43A. INSTRUMENTATION (B1) Barth, H. G. Adv. Chem. Ser. 1995, No. 247, 3-11. (B2) Vreuls, J. J.; De Jong, G. J.; Ghijsen, R. T.; Brinkman, U. A. T. J. AOAC Int. 1994, 77, 306-27. (B3) Grob, K. J. Chromatogr., A 1995, 703, 265-76. (B4) Cortes, H. J.; Campbell, R. M.; Himes, R. P.; Pfeiffer, C. D. J. Microcolumn Sep. 1992, 4, 239-44. (B5) Senorans, F. J.; Reglero, G.; Herraiz, M. J. Chromatogr. Sci. 1995, 33, 446-50. (B6) Blomberg, J.; Schoenmakers, P. J.; van den Hoed, N. J. High Resolut. Chromatogr. 1994, 17, 411-4. (B7) van Asten, A. C.; van Dam, R. J.; Kok, W. Th.; Tijssen, R.; Poppe, H. J. Chromatogr., A 1995, 703, 245-63. (B8) Yoo, J.; Watson, J. T.; McGuffin, V. L. J. Microcolumn Sep. 1993, 4, 349-62. (B9) Kassel, D. B.; Consler, T. G.; Shalaby, M.; Sekhri, P.; Gordon, N.; Nadler, T. In Techniques in Protein Chemistry VI 8th; meeting date 1994; Crabb, J. W., Ed.; Academic: San Diego, CA, 1995; pp 39-46. (B10) Holland, L. A.; Jorgenson, J. W. Anal. Chem. 1995, 67, 327583. (B11) Emmer, A.; Jansson, M.; Roeraade, J.; Lindberg, U.; Hoek,. B. J. Microcolumn Sep. 1992, 4, 13-5. (B12) Manz, A.; Verpoorte, E.; Effenhauser, C. S.; Burggraf, N.; Raymond, D. E.; Harrison, D. J.; Widmer, H. M. J. High Resolut. Chromatogr. 1993, 16, 433-6. (B13) Jacobson, S. C.; Hergenroeder, R.; Koutny, L. B.; Ramsey, J. M. Anal. Chem. 1994, 66, 2369-73. (B14) van de Merbel, N. C.; Brinkman, U. A. T. Trends Anal. Chem. 1993, 12, 249-56. (B15) Rodier, D. R.; Birks, J. W. Chromatographia 1994, 39, 4550. (B16) Bowman, P. B.; Marr, J. G. D.; Salvat, D. J.; Thompson, B. E. J. Pharm. Biomed. Anal. 1993, 11, 1303-15. (B17) Boughtflower, R. J.; Underwood, T.; Paterson, C. J. Chromatographia 1995, 40, 329-35. (B18) Coufal, P.; Claessens, H. A.; Cramers, C. A. J. Liq. Chromatogr. 1993, 16, 3623-52. (B19) Crego, A. L.; Dabrio, M. V.; Diez-Masa, J. C. J. Chromatogr. 1994, 659 255-9. (B20) Shoikhet, K.; Engelhardt, H. Chromatographia 1994, 38, 42130. (B21) Berloni, A.; Cappiello, A.; Famiglini, G.; Palma, P. Chromatographia 1994, 39, 279-84. ELEMENTAL DETECTORS (C1) Vela, N. P.; Caruso, J. A. J. Anal. At. Spectrom. 1993, 8, 78794. (C2) Sheppard, B. S.; Caruso, J. A. J. Anal. At. Spectrom. 1994, 9, 145-9. (C3) Seubert, A. Fresenius’ J. Anal. Chem. 1994, 350, 210-20. (C4) Culp, R. C.; Ng, K. C. Adv. At. Spectrosc. 1995, 2, 215-83. (C5) Long, G. L.; Ducatte, G. R.; Lancaster, E. D. Spectrochim. Acta, Part B 1994, 49B, 75-87. 596R
Analytical Chemistry, Vol. 68, No. 12, June 15, 1996
(C6) Weber, G.; Berndt, H. Int. J. Environ. Anal. Chem. 1993, 52, 195-202. (C7) Wichems, D. N.; Jones, B. T. Appl. Spectrosc. 1994, 48, 2735. (C8) Allen, L. B.; Koropchak, J. A. J. Chromatogr. 1993, 657, 1928. (C9) Gotz, R.; Elgersma, J. W.; Kraak, J. C.; Poppe, H. Spectrochim. Acta, Part B 1994, 49B, 761-8. (C10) Heumann, K. G.; Rottmann, L.; Vogel, J. J. Anal. At. Spectrom. 1994, 9, 1351-5. (C11) Bendicho, C. Anal. Chem. 1994, 66, 4375-81. (C12) Wu, M.; Madrid, Y.; Auxier, J. A.; Hieftje, G. M. Anal. Chim. Acta 1994, 286, 155-67. (C13) Mason, P. B.; Zhang, L.; Carnahan, J. W.; Winans, R. E. Anal. Chem. 1993, 65, 2596-600. UV-VISIBLE, AND RAMAN DETECTORS (D1) Svensson, L. M.; Markides, K. E. J. Microcolumn Sep. 1994, 6, 409-414. (D2) Rinke, G.; Hartig, C. Anal. Chem. 1995, 67, 2308-13. (D3) Synovec, R. E.; Sulya, A. W.; Burgess, L. W.; Foster, M. D.; Bruckner, C. A. Anal. Chem. 1995, 67, 473-81. (D4) Yang, J.; Griffiths, P. R. Proc. SPIE-Int. Soc. Opt. Eng. 1993, 2089, 336-7. (D5) Somsen, G. W.; Gooijer, C.; Brinkman, U. A. Th.; Velthorst, N. H. Proc. SPIE-Int. Soc. Opt. Eng. 1993, 2089, 536-7. (D6) Howdle, S. M.; Best, S. P. J. Raman Spectrosc. 1993, 24, 4435. (D7) Cabalin, L. M.; Ruperez, A.; Laserna, J. J. Talanta 1993, 40, 1741-7. FLUORESCENCE DETECTORS (E1) Shear, J. B.; Dadoo, R. Fishman, H. A.; Scheller, R. H.; Zare, R. N. Anal. Chem. 1993, 65, 2977-82. (E2) van de Nesse, R. J.; Hoornweg, G. Ph.; Gooijer, C.; Brinkman, U. A. Th.; Velthorst, N. H.; Law, B. Anal. Chim. Acta 1993 281, 373-83. (E3) Smalley, M. B. Shaver, J. M.; McGown, L. B. Anal. Chem. 1993, 65, 3466-72. (E4) Takeuchi, T.; Miwa, T. Anal. Chim. Acta 1994, 292, 275-9. (E5) Takeuchi, T.; Miwa, T. Chromatographia 1994, 38, 555-8. (E6) Oosterkamp, A. J.; Irth, H.; Tjaden, U. R.; van der Greef, J. Anal. Chem. 1994, 66, 4295-301. (E7) van de Nesse, R. J.; Vinkenburg, I. H.; Jonker, R. H. J.; Hoornweg, G. Ph.; Gooijer, C.; Brinkman, U. A. Th.; Velthorst, N. H. Appl. Spectrosc. 1994, 48, 788-95. (E8) Abbas, A. A.; Shelly, D. C. J. Chromatogr., A 1995, 691, 3753. (E9) Gooijer, C.; van de Nesse, R. J.; Mank, A. J. G.; Ariese, F.; Brinkman, U. A. Th.; Velthorst, N. H. Spec. Publ.-R. Soc. Chem. 1994, 154 (Reviews on Analytical ChemistrysEuroanalysis VIII), 153-67. (E10) Smalley, M. B.; McGown, L. B. Anal. Chem. 1995, 67, 13716. (E11) Takeuchi, T.; Miwa, T. Chromatographia 1995, 40, 159-62. (E12) Mank, A. J. G.; Velthorst, N. H.; Brinkman, U. A. Th.; Gooijer, C. J. Chromatogr., A 1995, 695, 165-74. (E13) Mank, A. J. G.; Velthorst, N. H.; Brinkman, U. A. Th.; Gooijer, C. J. Chromatogr., A 1995, 695, 175-83. (E14) van de Nesse, Ronald J.; van der Wegen, Robertes J.; Gooijer, Cees; Brinkman, Udo A. Th.; Velthorst, Nel H. Anal. Chim. Acta 1995, 309, 135-44. (E15) Karnes, H. T.; Rahavendran, S. V.; Gui, M. Proc. SPIE-Int. Soc. Opt. Eng. 1995, 2388 (Advances in Fluorescence Sensing Technology II), 21-31. (E16) van de Nesse, R. J.; Velthorst, N. H.; Brinkman, U. A. Th.; Gooijer, C. J. Chromatogr., A, 1995, 704, 1-25. (E17) Johnston, T.. E. Anal. Chem. 1995, 67, 2835-41. (E18) Takeuchi, T.; Miwa, T. Chromatographia 1995, 40, 545-9. (E19) Takeuchi, T.; Miwa, T. Anal. Chim. Acta 1995, 311, 231-6. (E20) Mank, A. J. G.; Yeung, E. S. J. Chromatogr., A 1995, 708, 30921. (E21) Kuklenyik, P.; Patonay, G. Instrum. Sci. Technol. 1995, 23, 113-22. CHEMILUMINESENCE DETECTORS (F1) Niederlaender, H. A. G.; Gooijer, C.; Velthorst, N. H. Anal. Chim. Acta 1994, 285, 143-59. (F2) Walters, D. L.; James, J. E.; Vest, F. B.; Karnes, H. T. Biomed. Chromatogr. 1994, 8, 207-11. (F3) Niederlaender, H. A. G.; Nuijens, M. J.; Dozy, E. M.; Gooijer, C.; Velthorst, N. H. Anal. Chim. Acta 1994, 297, 349-68. (F4) Ryerson, T. B.; Dunham, A. J.; Barkley, R. M.; Sievers, R. E. Anal. Chem. 1994, 66, 2841-51. (F5) Gilman, S. D.; Silverman, C. E.; Ewing, A. G. J. Microcolumn Sep. 1994, 6, 97-106. MASS SPECTROMETRY DETECTORS (G1) Pullen, F. S.; Richards, D. S. Rapid Commun. Mass Spectrom. 1995, 9, 188-90. (G2) Creaser, C. S.; Stygall, J. W. Analyst 1993, 118, 1467-80. (G3) Garcia, J. F.; Barcelo, D. J. High Resolut. Chromatogr. 1993, 16, 633-41.
(G4) Voyksner, R. D. Environ. Sci. Technol. 1994, 28, 118A-27A. (G5) Bruins, A. P. Trends Anal. Chem. 1994, 13, 37-43. (G6) Caprioli, R. M. Biological Mass Spectrometry: Present and Future [Proc. Kyoto ‘92 Int. Conf.]; Matsuo, T., et al., Eds.; Wiley: Chichester, UK, 1994, pp 75-100. (G7) Stroh, J. G.; Rinehart, K. L. Top. Mass Spectrom. 1994, 1, 287311. (G8) Linscheid, M.; Westmoreland, D. G. Pure Appl. Chem. 1994, 66, 1913-30. (G9) Niessen, W. M. A.; Tinke, A. P. J. Chromatogr., A 1995, 703, 37-57. (G10) Carey, J. M.; Byrdy, F. A.; Caruso, J. A. J. Chromatogr. Sci. 1993, 31, 330-44. (G11) Bruins, A. P. Trends Anal. Chem. 1994, 13, 81-90. (G12) Cappiello, A.; Famiglini, G. Anal. Chem. 1994, 66, 3970-6. (G13) Cappiello, A.; Famiglini, G. Anal. Chem. 1995, 67, 412-9. (G14) Bellar, T. A.; Budde, W. L. J. Am. Soc. Mass Spectrom. 1994, 5, 908-12. (G15) Wilkes, J. G.; Zarrin, F.; Lay, J. O., Jr.; Vestal, M. L. Rapid Commun. Mass Spectrom. 1995, 9, 133-7. (G16) He, X.; Brindle, I. D.; Jones, T. R. B.; Miller, J. M.; Singh, R. P. Rapid Commun. Mass Spectrom. 1995, 9, 150-5. (G17) Huang, S. K.; Garza, N. R. J. Am. Soc. Mass Spectrom. 1995, 6, 507-12. (G18) Caimi, R. J.; Brenna, J. T. Anal. Chem. 1993, 65, 3497-500. (G19) Purser, K. H. Nucl. Instrum. Methods Phys. Res., Sect. B 1994, 92, 201-6. (G20) Tomlinson, M. J.; Lin, L.; Caruso, J. A. Analyst 1995, 120, 583-9. (G21) Roboz, J.; Yu, Q.; Meng, A.; van Soest, R. Rapid Commun. Mass Spectrom. 1994, 8, 621-6. (G22) Eshraghi, J.; Chowdhury, S. K. Anal. Chem. 1993, 65, 352833. (G23) Hopfgartner, G.; Bean, K.; Henion, J.; Henry, R. J. Chromatogr. 1993, 647, 51-61. (G24) Reiser, R. W.; Fogiel, A. J. Rapid Commun. Mass Spectrom. 1994, 8, 252-7. (G25) Emmett, M. R.; Caprioli, R. M. J. Am. Soc. Mass Spectrom. 1994, 5, 605-13. (G26) Chen, Y.; Hill, H. H., Jr.; Wittmer, D. P. J. Microcolumn Sep. 1994, 6, 515-24. (G27) Wilkes, J. G.; Freeman, J. P.; Heinze, T. M.; Lay, J. O., Jr.; Vestal, M. L. Rapid Commun. Mass Spectrom. 1995, 9, 13842. (G28) Murray, K. K.; Lewis, T. M.; Beeson, M. D.; Russell, D. H. Anal. Chem. 1994, 66, 1601-9. (G29) Wang, A. P. L.; Guo, X.; Li, L. Anal. Chem. 1994, 66, 366475. (G30) Asakawa, N.; Ohe, H.; Oda, Y.; Mano, N.; Shikata, Y.; Yoshida, Y.; Sato, T. J. Mass Spectrom. Soc. Jpn. 1994, 42, 25-33. (G31) Gordon, D.; Lord, G.; Jones, D. Rapid Commun. Mass Spectrom. 1994, 8, 544-8. (G32) Tinke, A. P.; Niessen, W. M. A.; Tjaden, U. R.; van der Greef, J. Anal. Chem. 1994, 66, 3005-12. (G33) Carazzato, D.; Bertrand, M. J. J. Am. Soc. Mass Spectrom. 1994, 5, 305-15. (G34) Qian, M. G.; Lubman, D. M. Anal. Chem. 1995, 67, 287077. (G35) Debets, A. J. J.; Mekes, T. J. L.; Ritburg, A.; Jacobs, P. L. J. High Resolut. Chromatogr. 1995 18, 45-8. (G36) Jones, T. L.; Betowski, L. D.; Lopez Avila, V. Trends Anal. Chem. 1994, 13, 333-8. (G37) Jones, T. L.; Betowski, L. D.; Lopez-Avila, V. Trends Anal. Chem. 1994, 13, 333-8. ELECTROCHEMICAL DETECTORS (H1) Ewing, A. G.; Mesaros, J. M.; Gavin, P. F. Anal. Chem. 1994, 66, 527A-37A. (H2) Warner, M. Anal. Chem. 1994, 66, 601A-6A. (H3) Niwa, O.; Tabei, H.; Solomon, B. P.; Xie,F.; Kissinger, P. T. J. Chromatogr., B: Biomed. Appl. 1995, 670, 21-8. (H4) Tudos, A. J.; Van Dyck, M. M. C.; Poppe, H.; Kok, W. T. Chromatographia 1993, 37, 79-85. (H5) Ruban, V. J. High Resolut. Chromatogr. 1993, 16, 663-5. (H6) Bohs, C. E.; Linhares, M. C.; Kissinger, P T. Curr. Sep. 1994, 12, 181-6. (H7) Siddiqui, A.; Shelly, D. C. J. Chromatogr., A 1995, 691, 5565. (H8) Just, P.; Karakaplan, M.; Henze, G.; Scholz, F. Fresenius’ J. Anal. Chem. 1993, 345, 32-5. (H9) Kawaguchi, T.; Yamauchi, Y.; Maeda, H.; Ohmori, H. Chem. Pharm. Bull. 1993, 41, 1601-3. (H10) Ortiz, P. I.; Abu Nader, P. R.; Mottola, H. A. Electroanalysis 1993, 5, 165-9. (H11) Stitz, A.; Buchberger, W. Electroanalysis 1994, 6, 251-8. (H12) van Riel, J. A. M.; Olieman, C. Anal. Chem. 1995, 67, 39115. (H13) Casella, I. G.; Marchese, R. Anal. Chim. Acta 1995, 311, 199210. (H14) Casella, I. G. Anal. Chim. Acta 1995, 311, 37-46. (H15) Vandenberg, P J; Johnson D C Anal. Chim. Acta 1994, 290, 317-27. (H16) Marioli, J. M.; Luo, P. F.; Kuwana, T. Anal. Chim. Acta 1993, 282, 571-80. (H17) Luo, P. F.; Kuwana, T. Anal. Chem. 1994, 66, 2775-82.
(H18) Roberts, R. E.; Johnson, D. C. Electroanalysis 1994, 6, 26973. (H19) Roush, J. A.; Anderson, M. R. J. Liq. Chromatogr. 1993, 16, 3887-901. (H20) Slater, J. M.; Watt, E. J. Analyst 1994, 119, 273-7. (H21) Isildak, I.; Covington, A. K. Electroanalysis 1993, 5, 815-24. (H22) Macher, M.; Wintersteiger, R. J. Chromatogr., A 1995, 709, 257-64. NMR DETECTORS (I1) Albert, K. J. Chromatogr., A 1995, 703, 123-47. (I2) Stevenson, S.; Dorn, H. C. Anal. Chem. 1994, 66, 2993-9. (I3) Wu, N.; Peck, T.; Webb, A.; Magin, R.; Sweedler, J. J. Am. Chem. Soc. 1994, 116, 7929. (I4) Wu, N.; Peck, T.; Webb, A.; Magin, R.; Sweedler, J. Anal. Chem. 1994, 66, 3849-57. (I5) Wu, N.; Peck, T.; Webb, A.; Magin, R.; Sweedler, J. Anal. Chem. 1995, 67, 3101. (I6) Pullen, F. k. S.; Swanson, A. G.; Newman, M. J.; Richards, D. S. Rapid Commun. Mass Spectrom. 1995, 9, 1003-6. OTHER DETECTORS (J1) Saz, J. M.; Diez-Masa, J. C. J. Liq. Chromatogr. 1994, 17, 499520. (J2) Snook, J. D.; Lowe, R. D. Analyst 1995, 120, 2051-68. (J3) Rosenzweig, Z.; Yeung, E. S. Appl. Spectrosc. 1993, 47, 11759. (J4) Sanchis Mallols, J. M.; Villanueva Camanas, R. M.; RamisRamos, G. Anal. Lett. 1994, 27, 2011-26. (J5) Tran, C. D.; Huang, G.;. Grishko, V. I. Anal. Chim. Acta 1995, 299, 361-9. (J6) Faubel, W.; Schulz, T.; Seidel, B. S.; Steinle, E.; Ache, H. J. J. Phys. IV 1994, 4 (C7 8th International Topical Meeting on Photoacoustic and Photothermal Phenomena, 1994), 531-4. (J7) Rosenzweig, Z.; Yeung, E. S. Appl. Spectrosc. 1993, 47, 201721. (J8) Nunes, J. A.; Berniolles, S.; Tong, W. G. Proc. SPIE-Int. Soc. Opt. Eng. 1995, 2388 (Advances in Fluorescence Sensing Technology II), 205-12. (J9) Tran, C. D.; Grishko, V. I.; Huang, G. Anal. Chem. 1994, 66, 2630-5. (J10) Hayakawa, K.; Yamamoto, A.; Matsunaga, A.; Mizukami, E.; Nishimura, M.; Miyazaki, M. Biomed. Chromatogr. 1994, 8, 130-3. (J11) Yamamoto, A.; Matsunaga, A.; Mizukami, E.; Hayakawa, K.; Miyazaki, M.; Nishimura, M.; (Kitaoka, M.; Fujita, T. Analyst 1995, 120, 1137-9. (J12) Dappen, R.; Voight, P.; Maystre, F.; Bruno, A. E. Anal. Chim. Acta 1993, 282, 47-54. (J13) Castillo, J. R.; Cepria, G.; de Marcos, S.; Galban, J.; Mateo, J.; Garcia Ruiz, E. Sens. Actuators, A 1993 37-38, 582-6. (J14) Cepria, G.; Castillo, J. R. Quim. Anal. 1994, 13, 63-6. (J15) Lewis, K. C.; Dohmeier, D. M.; Jorgenson, J. W.; Kaufman, S. L.; Zarrin, F.; Dorman, F. D. Anal. Chem. 1994, 66, 2285-92. (J16) Allen, L. B.; Koropchak, J. A.; Szostek, B. Anal. Chem. 1995, 67, 659-66. (J17) Kientz, C. E.; Brinkman, U. A. T. Trends Anal. Chem. 1993, 12, 363-73. (J18) Conte, E. D.; Barry, E. F. Microchem. J. 1993, 48, 365-71. (J19) Bernard, J.; Nicodemo, T.; Barthakur, N. N.; Blais, J. S. Analyst 1994, 119, 1475-81. (J20) Howard, A. L.; Thomas, C. L. B.; Taylor, L. T. Anal. Chem. 1994, 66, 1432-7. (J21) Zegers, B. N.; Hessels, R.; Jagesar, J.; Rozenbrand, J.; Lingeman, H.; Brinkman, U. A. Th. J. Liq. Chromatogr. 1995, 18, 41340. (J22) Zegers, B. N.; de Brouwer, J. F. C.; Poppema, A.; Lingeman, H.; Brinkman, U. A. Th. Anal. Chim. Acta 1995, 304, 47-56. (J23) Lima, L. R., III; Dunphy, D. R.;. Synovec, R. E. Anal. Chem. 1994, 66, 1209-16. (J24) Lima, L. R., III; Synovec, R. E. J. Chromatogr. 1995, A, 691, 195-204. (J25) Gale, R. J.; Li, H. Proc.-Electrochem. Soc. 1993, 93-7 (Proceedings of the Symposium on Chemical Sensors II, 1993), 22735. (J26) Emneus, J.; Marko-Varga, G. J. Chromatogr., A 1995, 703, 191-243. (J27) Vanderlaan, M.; Lotti, R.; Siek, G.; King, D.; Goldstein, M. J. Chromatogr., A 1995, 711, 23-31. (J28) Krull, I. S.; Szulc, M. E.; Bourque, A. J.; Zhou, F.-X.; Yu, J.; Strong, R. J. Chromatogr., B 1994, 659, 19-50. (J29) Rubio, R.; Alberti, J.; Padro, A.; Rauret, G. Trends Anal. Chem. 1995, 14, 274-9. (J30) Billedeau, S. M.; Heinze, T. M.; Wilkes, J. G.; Thompson, H. C., Jr. J. Chromatogr., A 1994, 688, 55-65. COMPUTATION (K1) Bryant, C. H.; Adam, A.; Taylor, D. R.; Rowe, R. C. Anal. Chim. Acta 1994, 297, 317-47. (K2) Poe, R. B.; Rutan, S. C. Anal. Chim. Acta 1993, 283, 845-53. (K3) Gilliard, J. A.; Cumps, J. L.; Tilquin, B. L. Chemom. Intell. Lab. Syst. 1993, 21, 235-42.
Analytical Chemistry, Vol. 68, No. 12, June 15, 1996
597R
(K4) Tauler, R.; Barcelo, D. Trends Anal. Chem. 1993, 12, 31927. (K5) Vanslyke, S. J.; Wentzell, P. D. Chemom. Intell. Lab. Syst. 1993, 20, 183-95. (K6) Schostack, K. J.; Malinowski, E. R. Chemom. Intell. Lab. Syst. 1993, 20, 173-82. (K7) Keller, H. R.; Kiechle, P.; Erni, F.; Massart, D. L.; Excoffier, J. L. J. Chromatogr. 1993, 641, 1-9. (K8) Bakken, G. A.; Kalivas, J. H. Anal. Chim. Acta 1995, 300, 173-81. (K9) Cuesta-Sanchez, F.; Massart, D. L. Anal. Chim. Acta 1994, 298, 331-9. (K10) Sanchez, F. C. ; Lewi, P. J.; Massart, D. L. Chemom. Intell. Lab. Syst. 1994, 25, 157-77. (K11) Sanchez, F. C.; Khots, M. S.; Massart, D. L.; De Beer, J. O. Anal. Chim. Acta 1994, 285, 181-92. (K12) Sanchez, F. C,; Khots, M. S.; Massart, D. L. Anal. Chim. Acta 1994, 290, 249-58. (K13) Elbergali, A. K.; Brereton, R. G. Chemom. Intell. Lab. Syst. 1994, 23 97-106.
598R
Analytical Chemistry, Vol. 68, No. 12, June 15, 1996
(K14) Wentzell, P. D.; Hughes, S. G.; Vanslyke, S. J. Anal. Chim. Acta 1995, 307, 459-470. (K15) Tauler, InCINC’94sFirst Int. Chemom. InterNet Conf. 1994, http://www.emsl.pnl.gov:2080/docs/incinc/n_way_anal/RTdoc.html. (K16) Fabre, H.; Le Bris, A.; Blanchin, M. D. J. Chromatogr., A 1995, 697, 81-8. (K17) Lockmuller, C. H.; Reese, Charles; Hsu, S.-H. Anal. Chem. 1994, 66, 3806-13. (K18) Stauffer, S. T.; Dessy, R. E. J. Chromatogr. Sci. 1994, 32, 22835. (K19) Olsen, B. A.; Sullivan, G. R. J. Chromatogr., A 1995, 692, 14759. (K20) Josefson, M.; Klick, S.; Larsson, S.; Tekenbergs-Hjelte, L. Chemom. Intell. Lab. Syst. 1994, 23, 87-95. (K21) Bahowick, T. J.; Dunphy, D. R.; Synovec, R. E. J. Chromatogr., A 1994, 663, 135-50.
A19600092
