Cleanup by Sep-Pak silica cartridge and high performance liquid chromatographic determination of linear alkylbenzene sulfonates in sediment.

Abstract

A simple cleanup method with Sep-Pak silica cartridge (Waters Associates) was developed for the determination of linear alkylbenzene sulfonates (LAS) in sediment by high performance liquid chromatograph (HPLC) equipped with a fluorescence detector. The Sep-Pak silica cartridge treatment was extremely effective to remove co-existing interferences which appeared as an unresolved peak to the peaks for dodecylbenzene sulfonates in liquid chromatograms. Ten g of a sediment sample was extracted twice with 10 ml of methanol using a ultrasonic apparatus. After centrifugation, the combined extract was concentrated and dried up. The residue was dissolved in 2 ml of chloroform ; the chloroform layer was loaded to a Sep-Pak silica cartridge. After 10 ml of chloroform was passed through the cartridge, LAS was eluted with 4 ml of methanol. The eluate was concentrated and dried up. The residue was dissolved in 2 ml of methanol-water (7 : 3) for HPLC determination. Recoveries and coefficients of variations of LAS (0.938-11.7μg/g) added to 10 g of sediment were 89.6-108% and 7.0-7.3%, respectively ; the minimum determinable amount of LAS was 5 ng/g. This method was applied to determine LAS in sediments from small streams and the Shinano River ; the co-existing interferences in sediments were removed perfectly by the proposed cleanup method.