Coupling procedures, chromatographi

Richfield-Fratz, N., Bailey, Jr., J. E., and Bailey, C. J., Determination of unsul-phonated aromatic amines in FD C Yellow No. 6 by the diazotization and coupling procedure followed by reversed-phase high-performance liquid chromatography, /. Chromatogr., 331, 109, 1985. 

Of the methods developed for the identification of hydrocarbon mixtures, only coupled gas chromatography-mass spectrometry holds any real promise of certain identification and this only at a prohibitive cost in time spent characterising minor peaks. It would be far more efficient to develop rapid screening procedures which would eliminate all but a few possibilities, and then use gas chromatography-mass spectrometry to isolate and identify a few key peaks to confirm the characterisation. This is precisely the scheme adopted independently by a number of laboratories. 

Immunoaffinity chromatography cleanup has also been applied as an ideal and reliable strategy for residue analysis. Immunoaffinity columns prepared by coupling the antibodies to a cyanogen bromide-activated support were used to analyze avermectin BI residues in cattle tissues (359) and ivermectin in sheep serum (376). An immunoaffinity column prepared by an alternative activation/ coupling procedure with carbonyl diimidazole was also employed to analyze ivermectin residues in swine liver (361) since the earlier-reported methods did not work well in the analysis of this matrix. This recent work demonstrated the high specificity of tire antibody-mediated cleanup, but also showed that the immunoaffinity procedures could not always or completely eliminate matrix interference of samples. Therefore, application of additional cleanup steps before or after these procedures is often inevitable. 

N Richfield-Fratz, JE Bailey, CJ Bailey. Determination of unsulfonated aromatic amines in FD C yellow no. 6 by diazotization and coupling procedure followed by reverse-phase high performance liquid chromatography J Chromatogr 331 109-123, 1985. 

Frequently industrial hygiene analyses require the identification of unknown sample components. One of the most widely employed methods for this purpose is coupled gas chromatography/ mass spectrometry (GC/MS). With respect to interface with mass spectrometry, HPLC presently suffers a disadvantage in comparison to GC because instrumentation for routine application of HPLC/MS techniques is not available in many analytical chemistry laboratories (3). It is, however, anticipated that HPLC/MS systems will be more readily available in the future ( 5, 6, 1, 8). HPLC will then become an even more powerful analytical tool for use in occupational health chemistry. It is also important to note that conventional HPLC is presently adaptable to effective compound identification procedures other than direct mass spectrometry interface. These include relatively simple procedures for the recovery of sample components from column eluate as well as stop-flow techniques. Following recovery, a separated sample component may be subjected to, for example, direct probe mass spectrometry infra-red (IR), ultraviolet (UV), and visible spectrophotometry and fluorescence spectroscopy. The stopped flow technique may be used to obtain a fluorescence or a UV absorbance spectrum of a particular component as it elutes from the column. Such spectra can frequently be used to determine specific properties of the component for assistance in compound identification (9). 

Pommerening. Affinity Chromatography Practical and Theoretical Aspects Marcel Dekker, Inc. New York, 1985. Porath, J. General methods and coupling procedures. Methods Enzymol. 1974, 34, 13-30. 

At about the same time both Kaiser [336] and JanIk [319] independently described coupling techniques in which the plate moved along a so-called start line during deposition. JanIk described the coupling procedure primarily as a deposition method for TLC and paper chromatography. Kaiser pointed out that coupling served mainly to... 

Answers to 3. and 4. are clearly most important for preparative gas chromatography. It is thus possible to control neatly numerous discontinuous coupling procedures in which gas chromatography is the first stage interferences are disclosed. 

S. Palmarsdottir and L. E. Edholm, Enhancement of selectivity and concentration sensitivity in capillary zone electrophoresis by on-line coupling with column liquid chromatography and utilizing a double stacking procedure allowing for microliter injections , 7. Chromatogr. 693 131-143 (1995). 

Figure 13.5 Schematic presentation of the procedure involved in coupled-column RPLC AS, autosampler C-1 and C-2, first and second separation columns, respectively M-1 and M-2, mobile phases S-1 and S2, interferences A, target analytes HV, high-pressure valve D, detector. Reprinted from Journal of Chromatography, A 703, E. A. Hogendoom and R van Zoonen, Coupled-column reversed-phase liquid cliromatography in environmental analysis , pp. 149-166, copyright 1995, with permission from Elsevier Science.

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