Association of hydrophobic organic contaminants to size fraction of natural humic substances : using ultrafiltration and high-performance liquid chromatography

Abstract: Ultrafiltration and high-performance size exclusion chromatography (HPSEC) were used to determine interactions between different size-fractions of natural humic substance and carbofuran, lindane, chlorpyrifos and PCB-105. Ultrafiltration, using filter MWCO size of 1 kDa and 100 kDa, showed an adsorption of pesticide to filter. Chlorpyrifos (1 kDa) had the highest bioconcentration factor on filter (BCF) of 208±4.0. There was an overall trend of loss of pesticide recovery. Lindane had the lowest recovery 62±2.3% at 1 kDa. Fractionation using HPSEC gave different size-fractions of humic substance with recovered pesticide. However, HPLC/MS/MS showed that both carbofuran and chlorpyrifos fastened in the column. This was most likely the case for lindane also, although this could not be tested due to lindane’s volatility. PCB-105 was lost during incubation previous to HPSEC fractionation. When adding humic substance, there was a decreased adsorption of pesticide to filter (ultrafiltration) and column (HPSEC). Even though no pattern between pesticides and specific size fractions of humic substance could be detected, it is obvious that humic substance alters the behavior of HOC and making them more mobile.