Prediction of Soil Organic Partition Coefficients by a Soil Leaching Column Chromatographic Method

The soil organic partition coefficient ( K oc ) is one of the most important parameters to depict the transfer and fate of a chemical in the soil–water system. Predicting K oc by using a chromatographic technique has been developing into a convenient and low‐cost method. In this paper, a soil leaching column chromatograpy (SLCC) method employing the soil column packed with reference soil GSE 17201 (obtained from Bayer Landwirtschaftszentrum, Monheim, Germany) and methanol–water eluents was developed to predict the K oc of hydrophobic organic chemicals (HOCs), over a log K oc range of 4.8 orders of magnitude, from their capacity factors. The capacity factor with water as an eluent k ′ w could be obtained by linearly extrapolating capacity factors in methanol–water eluents ( k ′) with various volume fractions of methanol (φ). The important effects of solute activity coefficients in water on k ′ w and K oc were illustrated. Hence, the correlation between log K oc and log k ′ w (and log k ′) exists in the soil. The correlation coefficient ( r ) of the log K oc vs. log k ′ w correlation for 58 apolar and polar compounds could reach 0.987, while the correlation coefficients of the log K oc –log k ′ correlations were no less than 0.968, with φ ranging from 0 to 0.50. The smaller the φ, the higher the r Therefore, it is recommended that the eluent of smaller φ, such as water, be used for accurately estimating K oc Correspondingly, the r value of the log K oc –log k ′ w correlation on a reversed‐phase Hypersil ODS (Thermo Hypersil, Kleinostheim, Germany) column was less than 0.940 for the same solutes. The SLCC method could provide a more reliable route to predict K oc indirectly from a correlation with k ′ w than the reversed‐phase liquid chromatographic (RPLC) one.