Cloud point extraction for speciation analysis of inorganic tin in water samples by graphite furnace atomic absorption spectrometry

Abstract

A new method based on cloud point extraction (CPE) separation and graphite furnace atomic absorption spectrometry (GFAAS) detection was proposed for the determination of inorganic tin species. When the system temperature is higher than the cloud point extraction temperature (CPT) of the mixed surfactant of p-octyl polyethyleneglycolphenyl ether (Triton X-100) and sodium dodecyl sulfate(SDS), the complex of Sn(IV) with 1-(2-pyridylazo)-2-naphthol (PAN) could be extracted into the surfactant-rich phase, whereas the Sn(II) remained in the aqueous phase. Thus, an in situ separation of Sn(IV) and Sn(II) could be realized. The main factors affecting the cloud point extraction were investigated systematically. Under the optimized conditions, the determination limit for Sn(IV), as low as 0.51 ng mL⁻¹, was obtained by preconcentrating a 10 mL sample solution, and the relative standard deviation (n = 10; c = 1.0 mg L⁻¹) was 3.6%. The proposed method was applied to the speciation analysis of tin in different water samples and the recovery of total Sn was in the range of 98.9–100.7%. In order to verify the accuracy of the method, a certified reference water sample was analysed and the results obtained were in good agreement with the certified values.