Determination of organotin compounds in water and sediment samples by isotope dilution GC/MS

A method for the simple and rapid determination of organotins (monobutyl-, dibutyl-, tributyl-, monophenyl-, diphenyl- and triphenyltin), in water and sediment has been developed by isotope dilution GC/MS. After deuterated organotins as internal standards were added in a water sample, orgatotins were derivatized with NaBEt4 at pH 5; then, ethylated organotins were extracted with hexane and cleaned up by using a florisil minicolumn. In the case of a sediment sample, organotins were firstly extracted with 1 M HCl-methanol/ethyl acetate (1 : 1), and the extract was concentrated. Then, the concentrate was added to a buffer solution; the following procedures were performed in the same way as that for water. Instrument measurement was carried out by GC/MS-SIM. The results concerning the overall recovery tests at ng/l levels for water and μg/kg levels for sediments showed that the mean recoveries were 104 and 98.1%, respectively. Their mean relative standard deviations were 3.7 and 9.8%, respectively. The detection limits of the method for target chemicals ranged from 0.16 to 3.5 ng/l for water, which were about one order lower than that by the conventional methods, and from 0.48 to 11 μg/kg for sediment. The method was applied to real samples; di- and trisubstituted organotins were detected in seawater and sediment, but only dibutyltin was found in river water.