EVALUATION OF THEORETICAL-MODELS OF NON ELECTROLYTE-SOLUTIONS IN THE PREDICTION OF KOVATS RETENTION INDEXES OF BRANCHED ALKANES IN ALKANE STATIONARY PHASES

The models of Flory and of Elbro et al. were used for the prediction o f Kovats retention indices of alkane solutes in squalane at three temp eratures. The results were compared with experimental indices for sixt y-two alkanes containing six to nine carbon atoms. Both models resulte d in a better agreement with experimental indices than former predicti on methods. A linear relationship was found between (I-X-I(X)) and (V -X-V-N), where I-X, I(X) and V-X represent the experimental index, th e calculated index and the molar volume of solute X, and V-N is the mo lar volume of its isomeric normal alkane. The application of a correct ion formula based on this finding lowered the errors of the prediction to a half of its original value. Errors in the retention indices pred icted by the model recently proposed by Kontogeorgis et al. [Fluid Pha se Equilibria, 92 (1994) 35] were affected by temperature.