Calculation of retention indices of compounds from their structural formulae for combined identification by gas chromatography-mass spectrometry: Application to aliphatic alcohols and saturated hydrocarbons

Abstract

A method of choosing structural groups based on the types or “forms” of bonds present for calculation of Kováts retention indices using the additivity principle is given. The form of a chemical bond and its immediate surroundings reflects the valency state of all of the atoms included and is considered to introduce an independent contribution to the retention index. In accordance with this assumption, the combined treatment of the retention data of compounds of different classes is possible in order to calculate the partial contributions of several structural groups. The values obtained by combined processing of retention data for saturated hydrocarbons and aliphatic alcohols were in satisfactory agreement with the results calculated by separate treatment of the retention data for hydrocarbons. The mean-square error of the calculated values of retention indices with respect to the experimental values is 7 retention index units. The accuracy achieved permits the use of this method in combined gas chromatographic-mass spectrometric identification. The possibility of calculating retention indices based on the structural formulae of compounds drastically reduces the number of possible structures suggested by mass spectrometric data. The calculation method presented here is suitable for computer calculations. The accuracy of the calculation is sufficient for the required purpose.