Linear solvation energy relationships regarding sorption and retention properties of hydrophobic organic compounds in soil leaching column chromatography

The capacity factors of a series of hydrophobic organic compounds (HOCs) were measured in soil leaching column chromatography (SLCC) on a soil column, and in reversed-phase liquid chromatography on a C18 column with different volumetric fractions ( ) of methanol in methanol–water mixtures. A general equation of linear solvation energy relationships, log(XYZ)=XYZ0+mVI/100+sπ*+bβm+aαm, was applied to analyze capacity factors (k′), soil organic partition coefficients (Koc) and octanol–water partition coefficients (P). The analyses exhibited high accuracy. The chief solute factors that control logKoc, logP, and logk′ (on soil and on C18) are the solute size (VI/100) and hydrogen-bond basicity (βm). Less important solute factors are the dipolarity/polarizability (π*) and hydrogen-bond acidity (αm). Log k′ on soil and logKoc have similar signs in four fitting coefficients (m, s, b and a) and similar ratios (m:s:b:a), while logk′ on C18 and logP have similar signs in coefficients (m, s, b and a) and similar ratios (m:s:b:a). Consequently, logk′ values on C18 have good correlations with logP (r>0.97), while logk′ values on soil have good correlations with logKoc (r>0.98). Two Koc estimation methods were developed, one through solute solvatochromic parameters, and the other through correlations with k′ on soil. For HOCs, a linear relationship between logarithmic capacity factor and methanol composition in methanol–water mixtures could also be derived in SLCC.