The effect of humic acid and ash on enantiomeric fraction change of chiral pollutants

The aim of the study was to determine changes of enantiomeric fraction (EF) of chiral compounds interacting with components of soil and to describe the effect of amount of soil components on EF value. Soil components (humic acid and ash) were isolated from soil using method recommended by the International Humic Substance Society (IHSS). Dichloromethane was used as an extraction solvent for extraction of polychlorinated biphenyls (PCBs), mecoprop and its methyl ester enantiomers from humic acid (HA) and ash. The extracts were analyzed by a high performance liquid chromatography (HPLC). HPLC columns filled with silica gel modified by permethylated cyclodextrine acting as a chiral selector were used for analytical separation of enantiomers. The results confirm the stereoselective effect of soil components on extractable amount of individual enantiomers. Significant changes of EF of chiral pollutants were observed for investigated PCBs enantiomers (HA 0.49–0.45, ash 0.50–0.58) and for mecoprop-methyl ester (HA 0.55–0.59, ash 0.49–0.34), smaller changes of EF were observed for mecoprop (HA 0.52–0.50, ash 0.49–0.50). The changes of EF were dependent on an amount of humic acid and ash. Inverse trends of humic acid EF changes were obtained comparing to trends of EF changes of ash.