Rapid and direct speciation of methyltins in seawater by an on-line coupled high performance liquid chromatography–hydride generation–ICP/MS system

A novel on-line coupled HPLC–hydride generation (HG)–ICP/MS system was developed for rapid, direct and sensitive speciation of methyltins in seawater without any pretreatment step. Methyltin compounds were separated by reversed phase HPLC, and then on-line reacted with potassium borohydride and acetic acid to generate volatile hydride products. The volatile derivatization products were separated in the spray chamber of ICP/MS and then introduced into ICP/MS by argon gas for detection. Monomethyltin (MMT), dimethyltin (DMT) and trimethyltin (TMT) were baseline separated in less than 15 min by reversed phase HPLC. The influence of KBH4 concentration and type of acid on the system performance was investigated and optimized. Calibration curves, based on peak heights against concentration, were linear in the range of 0.5–50 ng (Sn) mL−1 of methyltins with correlation coefficients of 0.9990, 0.9990 and 0.9996 for MMT, DMT and TMT, respectively. The relative standard deviations measured at 10 ng (Sn) mL−1 for these three methyltins were in the range of 0.6–1.4% (n = 5), and the calculated detection limits (S/N = 3) for MMT, DMT and TMT were 0.266, 0.095 and 0.039 ng (Sn) mL−1, respectively. This method was successfully applied to the speciation of methyltins in seawater with spiked recovery in the range of 95.4–106.9%. MMT and DMT were detected in all the seawater samples with concentrations in the range of 1.0–1.5 and 0.30–0.57 ng (Sn) mL−1 for MMT and DMT, respectively.