On line coupling HPLC and quartz surface-induced luminescence FPD with hydride generation and microporous membrane gas–liquid separator as interface for the speciation of methyltins

Abstract

A novel on-line coupled high performance liquid chromatography (HPLC)-hydride generation (HG)-microporous membrane gas–liquid separator (MGLS)-quartz surface-induced luminescence flame photometric detector (QSIL-FPD) system was developed for the speciation of methyltins. Methyltin compounds were separated by HPLC, and then on-line reacted with potassium borohydride to generate volatile hydride products. The volatile derivatization products were in-line separated from the liquid matrix with MGLS and further introduced into the cheap and specific QSIL-FPD for detection. With a mobile phase of 70% methanol, 3% acetic acid and 27% water, which contains 0.1% tropolone as complexant, at a 0.3 mL min⁻¹ flow rate, monomethyltin (MMT), dimethyltin (DMT) and trimethyltin (TMT) were baseline separated in less than 13 minutes by reversed phase HPLC. Both derivatization reagents, 0.5% KBH₄ and 2% acetic acid, were introduced into the system simultaneously at the same flow rate of 0.4 mL min⁻¹. Calibration curves, based on peak heights vs. concentration, were linear in the range of 1–100 ng mL⁻¹ of methyltins with correlation coefficients of 0.9980, 0.9911 and 0.9975 for MMT, DMT and TMT, respectively. The relative standard deviations measured at 10 ng mL⁻¹ (for MMT and DMT) and 5 ng mL⁻¹ (for TMT) level were in the range of 2.0–3.8% (n = 3) for the studied methyltins, and the calculated detection limits (S/N = 3) for MMT, DMT and TMT were 1.69, 0.51 and 0.36 ng mL⁻¹, respectively. This developed method was applied to the speciation of methyltins in seawater with spiked recovery in the range of 95.9–100.7%. This method was also applied to the determination of the methyltin compounds in wastewater and the process solutions (the mixtures of methyltin trichloride and dimethyltin dichloride) which are the intermediates of methyltin mercaptide polyvinyl chloride heat stabilizer from a chemical factory.