Simultaneous preconcentration and quantification of ultra-trace tin and lead species in seawater by online SPE coupled with HPLC-ICP-MS

Background: Tin and lead contamination is a global threat to marine ecosystems considering their species -specific toxicity, bioavailability and mobility. Hence simultaneous measurement of multiple tin and lead compounds at mu g L-1 to pg L-1 levels in environmental water is always an indispensable but challengeable task. High performance liquid chromatography coupled with inductively coupled plasma mass spectrometry (HPLC-ICP-MS) is one of the most widely used choices for this purpose because of good sensitivity, strong separation power and good compatibility. Previous HPLC-ICP-MS methods based on a single elemental speciation strategy are lowefficiency and sensitivity -insufficient for a large set of unstable samples and interaction of multiple metal (loid)s down to ng L-1 levels. Results: In this study, we developed a sensitive, efficient and environment -friendly analytical method for accurate quantification of inorganic and organic species of tin and lead simultaneously based on HPLC-ICP-MS with online integration of solid phase extraction (SPE). By using graphene oxide modified silica conditioned with 1 mM benzoic acid to enrich tin and lead species from 10 mL sample, detection limits were improved to 2-8 pg per liter due to satisfactory enrichment factors (522-2848 folds). The SPE-HPLC-ICP-MS method was applicable to quantification of ultra -trace tin and lead species at pg L-1 levels in uncontaminated seawater. Tributyltin was the only tin species detected at subnanograms per liter levels while Pb(II) was the only lead species detected at several nanograms per liter in thirteen coastal seawater samples collected in Hangzhou Bay, indicating light contamination of tin and lead. Significance: Overall, the proposed SPE-HPLC-ICP-MS method is highly sensitive, efficient and environmentfriendly that are fairly suitable to routine speciation analysis of tin and lead in environmental, food, and biological samples.