J.K. Haken

Recent developments in the gas chromatographic retention index scheme

Abstract The development of the retention index over 30 years is summarised and advances that have occurred in recent years are highlighted. The Work follows an exhaustive review published by Budahegyi et al. in 1983, but is much more selective and does not include the many reports of isolated retention indices. The review includes alternative logarithmic index schemes and other reference series that have been reported and which were not included in the earlier work. The work concludes with a tabulation of recently available compilations of retention indices.

Gas chromatography of homologous esters : VI. Strucgure—retention increments of aliphatic esters

Abstract The influence of the polarity of the stationary phase on retention increments for the structural parameter of homologous series of aliphatic esters is detailed and the results are discussed in terms of the findings of earlier studies that have been reported where restricted ranges of solutes and solvents were considered.

Evaluation of procedures for the estimation of dead time

Abstract In order to determine the exact retention of compounds in gas chromatographic studies some method of determining the column dead time must be employed. This paper reviews direct measurement techniques using methane injection as well as mathematical determination of dead-time from retention data for n -alkanes. A critical evaluation of these procedures is made along with recommendations concerning the choice of evaluation method to be adopted by the chromatographer.

Developments in polysiloxane stationary phases in gas chromatography

Summary Although the requirements of stationary phases have continued to become more stringent with the development of instrumental techniques the polysiloxanes have remained as the major group of stationary phases. While the early industrial polysiloxane products have long been replaced by refined specially products, development has continued with the preparation of polysiloxanes specifically for gas chromatography and particularly capillary gas chromatography. The efficiency of polar capillary columns has been low but recent advances with immobilized phases have been most promising. The acknowledged thermal stability of the polysiloxane backbone has been employed in several ways. Such as with chiral pendant groups to facilitate the separation of optically active materials and with mesogenic groups to provide phases with superior properties to the low-molecular-weight liquid-crystal materials. Further modification of the polysiloxanes has been achieved by the inclusion of other metallic atoms. The most important development in recent years is the introduction of bonded or immobilized phases. Extensive studies have allowed the production of efficient polar capillary columns which are now commercially available.

Estimation of dead time and calculation of kovats indises

Abstract To increase the usefulness of gas chromatography, a method qf data presentation is required that removes interlaboratory variations. All such methods require the determination of the system dead time, with the most useful being the retention index system of Kovats. This paper reviews the many theoretical, experimental and mathematical methods of estimating system dead time and evaluates their usefulness, not only in the estimation of dead time, but also in the subsequent calculation of Kovats indices. Recommendations are made as to the appropriate method to be used, and the expected accuracy in retention index values is estimated.

Evaluation of mathematical procedures for the calculation of dead-time

Abstract An extensive study has been made of three methods of determining dead-times mathematically from retention data of n -alkanes. It has been shown that the linearization procedure suggested by Grobler and Balisz is sufficiently accurate for online data acquisition and that four alkanes are adequate to calculate accurately the dead-time provided that the retention times are not excessive.

A problem of accuracy of mathematical dead-time estimation

Abstract The problem of accurate determination of mathematical dead-time is discussed. A comparison of the several methods of calculation is made. The effect of small changes in retention time of n-alkanes on the calculated dead-time has been examined and reasons for inaccurate dead-time estimates are suggested.

Gas chromatography of homologous esters : IX. Structure-retention increments of unsaturated esters

Abstract The influence of the polarity of the stationary phase on retention increments of homologous and isomeric unsaturated esters is detailed and the results are discussed in terms of the findings of earlier studies that have been reported where restricted ranges of solutes and solvents were considered.

Gas chromatography of homologous esters: Part V. Retention of aliphatic esters on non-polar, donor and acceptor stationary phases

Abstract The retention behaviour of homologous saturated esters on polysiloxane stationary phases which vary in character from essentially non-polar to those of considerable polar character and exhibiting some donor and acceptor properties is reported. The influence of these factors on the relationship between boiling point and retention as reported on non-polar phases is discussed.

Retention time relationships in the gas chromatography of the methyl esters of fatty acids

Abstract The influence of structural parameters on the retention behaviour of the methyl esters of methylene-interrupted fatty acids, their monounsaturated and saturated homologs may be shown by a simple mathematical relationship.