Anal. Chem. 1902,5 4 , 470 R-428 R
Gas Chromatography Terence H. Rlsby Department of Environmental Health Sciences, Johns Hopkins University of Hygiene and Public Health, Baltimore, Maryland 2 1205
Larry R. Field Department of Chemistry, University of Washington, Seattle, Washington 98 195
Frank J. Yang and Stuart P. Cram* Walnut Creek Division, Varian Instrument Group, 2700 Mitchell Drive, Walnut Creek, California 94598
INTRODUCTION This review surveys the fundamental developments in the field of gas chromatography (GC) during the biennium since the publication of the last review in this series (1A) and covers the years 1980-1981. It is not intended to be a comprehensive bibliography of the GC literature. Rather, the authors have been highly selective in identifying the most fundamental developments for this review. A few application papers are cited for purposes of illustration, because they illustrate a new development and/or they are an integral portion of a fundamental contribution. One may conclude from the 1982 GC review that the GC te,chnique has basically matured. The new developments are in the fields of higher resolution, separations, specific detectors, and microprocessor control instruments and systems. Therefore, special emphasis has been given to these topics so as to be more comprehensive and critical. This trend toward increased performance is consistent with the increased demand for environmental and regulatory analyses, and the high sensitivity available with modern GC detectors. A large number of papers describing derivitization reactions continue to appear in the GC literature. This can be explained in part by the need for high sensitivity, element-specific detectqs and GC-MS analyses but should be significantly decreased by the application of the advances in HPLC. It is predicted that these same trends will continue throughout the 1980s. COLUMNS Column Theory and Techniques. Guiochon (2B)published an excellent theoretical paper comparing the theoretical limits of separation speed in both gas and liquid chromatography. Performance is defined as the time needed to generate a peak having a given efficiency. Fastest analysis is achieved when the inlet pressure is the maximum pressure at which the available equipment can work. Calculations were made for a number of different particle sizes, diffusion coefficients, and HETP equation coefficients. Laub (6B)examined three types of retention index schemes for the purposes of prediction of optimum stationary phase mixtures for chromatographic separation. Criteria for the use of each method were discussed. Novak et al. (7B)reported on the correlation of specific retention volumes of homologous compounds with temperature and methylene number. A mathematical expression was derived relating specific retention, temperature, and the number of methylene groups of the solute molecule: The accuracy of the V , values calculated is commensurate with the precision of replicate determinations of a given compound on a given instrument. The effect of temperature dependence on mobile phase viscosity on the retention time in series-coupled columns was examined by Buys and Smuts ( I B ) . Numerical results indicate that the temperature dependence of the viscosity coefficient affects the retention time a d the pressure drop, while the effective 410 R
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mass distribution coefficient remains essentially unchanged. Spencer and Rogers (13B) developed an algorithm for converting peak detection and tailing into chromatographic information. Predictions for each chromatographic datum were based on it relation to a threshold on previous data, and on Gaussian behavior. Several authors have addressed the problem of accurately determining dead time. Wainwright and Haken (15B) reviewed both direct measurement techniques and mathematical methods for the determination of column dead time. A critical evaluation of these procedures is made along with recommendations concerning the choice of evaluation method to be adopted by the chromatographer. Parcher and Johnson (8B)calculated accurate values for dead times using four inert gases and five hydrocarbons. In addition a linearization method was developed in which the solute probe methane was assigned an effective carbon number of 0.5. Kaguei et al. (4B) measured the effects of dead volume on the estimation of packed-bed parameters from inputoutput response curves. They found the effects of dead volume should not be ignored for glass beads but can be ignored for activated carbon. The effective porosity in a packed column of porous material was examined in detail by Kaizuma (5B). The microintraparticle pores of these materials hold most of the stationary phase inside them. These researchers found that there exists a rectangular hyperbolic relation between the retention time and the interdiffusion coefficient of the inert component of the carrier gas. This fact is explained by the diffusion kinetics between the mobile and stationary phases. Relations between chromatographic peak moments for a nonisobaric column were developed by Pazdernik and Schneider (9B)which take into consideration the dependence of the axial dispersion coefficient, mass transfer coefficient, and effective diffusion coefficient on the pressure drop across the column. On a more practical note, Dennings and Yabumoto (3B) studied the effect temperature on separation number. They found that the magnitude of the separation number varies inversely with column temperature and directly with the partition ratios of the test solutes. The interrelations of column temperature and partition ratios are also explored. A new approach to increased analysis rate and very large column plate numbers was introduced by Snyder et al. (12B) in the form of boxcar chromatography. This technique is a new form of column-switching which provides significantly faster separations. Partial separation of compounds of interest was performed on the first column, with diversion of the resulting fraction to a second column. The second column was filled with several samples at any given time. High-efficiency separations (column plate numbers > lo5 but
