Thallium (III) determination in the Baltic seawater samples by ICP MS after preconcentration on SGX C18 modified with DDTC

The main difficulty of speciation analysis of thallium lies in extremely low concentrations of TI(III) in comparison to TI(I), which is the dominating form of thallium in environmental samples. In this study, a sensitive method is presented for separation of trace amounts of TI(III) from TI(I) and preconcentration of TI(III) using octadecyl silica gel modified with diethyldithiocarbamate (DDTC). Under optimal conditions, only TI(III) is retained on the sorbent, and then eluted with 96% ethanol. After chemical decomposition of TI(III)-DDTC complex, thallium is determined by inductively coupled plasma mass spectrometry. High performance liquid chromatography with 1CP MS detection was used to control the correctness of the obtained results. Parameters affecting solid phase extraction (SPE) such as pH, type, concentration and volume of eluent, breakthrough volume, and the impact of sample salinity (chlorides) and other interfering ions (Cd(II), Zn(II), Pb(II), Cu(II), Sn(II)) were investigated. The limit of detection (LOD), evaluated for 2 mL of sample solution, was 0.10 ng for TI(I) and 0.43 ng for TI(III). The method was applied to the determination of TI(I) and TI(III) in the Baltic seawater samples enriched in both thallium species. (C) 2013 Elsevier B.V. All rights reserved.