Retention indices, in gas chromatography

H.L. Yin and Y.L. Sun, The achievement of reproducible temperature programmed retention indices in gas chromatography when using different columns and detectors, Chromatographia 29, 39-43 (1990). 

Wold, S. and Andersson, K. Major Components Influencing Retention Indices in Gas Chromatography. J. Chromatogr., 1973,80,43. 

Uehori R, Nagata T, Kimura K, et al. 1987. Screening of volatile compounds present in human blood using retention indices in gas chromatography. J Chromatogr 411 251-257. 

Nau, H. and Biemann, K. (1974), Computer assisted assignment of retention indices in gas chromatography - mass spectrometry and its application to mixtures of biological origin. Anal. Chem.y 46,426. 

This method as its name implies is based on the concept of retention indices from gas chromatography. So far the method only has group contribution units worked out for estimating the partitioning of organic substances between polyolefins in contact with ethanol and water but it gives very good estimations for these systems. 

The most commonly used retention parameter in gas chromatography is the Kovats index. When the adjusted retention times are used to calculate Kovats indices, retention parameters are obtained which depend only on the column temperature and the stationaiy phase used. Kovats indices are highly reproducible, and with a well designed experimental technique and an accurate timing mechanism, an inter-laboratory reproducibility of one unit for larger values of Kovats indices and two units for indices below 400 is possible [14]. Instead of Kovats indices, sometimes in QSRR studies the logarithms of retention volumes of solutes are used. 

Counterpropagation networks have been used in property prediction, QSAR, the prediction of retention indices, and Kovats indices in gas chromatography. " In the latter application these networks performed better than multilinear regression when the coefficient of determination (r ) was low but were worse when was high. Apparently, counterpropagation ANNs per-... 

Halang, W. A., Langlais, R., and Kugler, E., Cubic Spline Interpolation for the Calculation of Retention Indices in Temperature-Programmed Gas-Liquid Chromatography, Ana/. Chem. 50, 1978, 1829-1832. 

Kovat s retention indexes analychem Procedure to identify compounds in gas chromatography the behavior of a compound Is Indicated by Its position on a scale of normal alkane values (for example, methane = 100, ethane = 200). ko-vats ri ten-... 

The usefulness of retention data from gas chromatography can be enhanced by reporting standardized times or retention indices (RI), which involves expressing retention in terms of a ratio of the retention time (RT) of an analyte to the RT of a standard. Retention scaling based on the Kovats (1965) method requires the chromatographic separation of a homologous series of normal paraffins, esters, and others, producing an index that is the ratio of the RT of an analyte minus the RT of a less retentive standard to the RT difference between... 

Figure 6.4 Schematic example of the variation of retention with temperature in gas chromatography. Retention lines are drawn for a group of 8 solutes (e.g. homologues). Vertical dashed lines (a and b) correspond to chromatograms (a and b) in figure 6.1. Horizontal dashed lines indicate the range of optimum capacity factors.

Variation of temperature plays but a minor role in the optimization of relative retention values. Desty indicated that variation of the carrier gas can make small differences in relative retention values. Thus the relative retention values for benzene and 2,4-dimethylpentane are 1.009,1.017, and 1.012 for helium, nitrogen, and carbon dioxide at an inlet pressure of 2.9 atm. Since the carrier gas can do little to optimize relative retention values for the more difiScult separations in gas chromatography, the main recourse is to longer, more efficient columns. 

The retention indices were calculated as previously described by Popl et al. (45), with the hydrocarbon standards being assigned the following retention indices benzene, 10 naphthalene, 100 phenanthrene, 1000 benzanthracene, 10,000 and benzo[b]chrysene, 100,000. The retention index of an aromatic hydrocarbon was then calculated in a manner analogous to the calculation of Kovats indices for gas chromatography. 

Rohrschneider s approach is able to predict retention index values for solute s with known solute constants (a, through e) [283,288]. These are determined from AI values for the solute on at least five phases of known phase constants and solving the series of linear equations. The retention index of the solute on any phase of known phase constants (X through S ) can then be calculated from Eq. (2.8). The theoretical defects of the method for assigning intermolecular interactions do not apply to the prediction of retention index values. A mean error of about 6 index units was indicated in some calculations. The retention or retention index values for thousands of compounds can be calculated from literature compilations of solute descriptors and the system constants summarized in Tables 2.6 and 2.8 using the solvation parameter model [103]. The field of structure-driven prediction of retention in gas chromatography is not well developed at present and new approaches will likely emerge in the future. 

A scale was developed of relative hydrogen-bond basicity for a wide variety of compounds by means of their retention in gas chromatography. Results indicate that the... 

Halang, W.A. Langlais, R. Kugler, E. Cubic spline interpolation for tbe calculation of retention indices in temperature programming gas-hquid chromatography. Anal. Chem. 1978, 50 (13), 1829-1832. 

Evans, M.B. Haken, J.K. Toth, T.J. Solute characterization in gas chromatography by an extension of Kovats retention index system. Dispersion and selectivity indices. J. Chromatogr. 1986, 351,155-164. 

Shibamoto, T., 1987. Retention indices in essential oil analysis. In Capillary Gas Chromatography in Essential Oil Analysis, 1st edn., S. Sandra and C. Bicchi (eds.). Heidelberg, Germany Alfred Huethig... 

Zhu, S., X. Lu, Y. Qiu, T. Pang, H. Kong, C. Wu, and G. Xu, 2007. Determination of retention indices in constant inlet pressure mode and conversion among different column temperature conditions in comprehensive two-dimensional gas chromatography../. Chromatoer. A. 1150 28. 

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