New alternatives for estimating the octanol/water partition coefficient and water solubility for volatile organic compounds using GLC data (Kovàts retention indices)

Abstract

New possibilities for estimating octanol/water partition coefficients (logP) and the water solubility (Sw) were investigated using Kovàts retention indices (I) obtained from GLC retention data for 132 volatile organic compounds belonging to 7 different chemical classes (hydrocarbons, alcohols, aldehydes, ketones, carboxylic acids, esters and halogen compounds). Application of the multilinear regression method led to six equations, all involving index I, as follows: (i) direct correlation logP vs. I (eq.1); (ii) logP vs. I, molar refractivity, and surface tension (eq. 2); (iii) logP vs. I and structural characteristics (eqs. 3, 4 and 6); (iv) logP vs. the I/Sw ratio (eq. 5). Excepting eq. 1 (which showed relatively weak correlations), eqs. 2 - 6 can provide reliable values for logP and for log Sw as proved by the significant statistical parameters. The general models presented through eqs. 2 - 6 may also be applied in estimation of other biological and/or ecological important properties, which are linearly dependent on the logP or log Sw values. By generalization, a new calculation method is suggested (eq. 7), in order to allow the estimation of logP or log Sw in terms of the number of bonds and the Kovàts retention index.