On-line cloud point extraction combined with electrothermal vaporization inductively coupled plasma atomic emission spectrometry for the speciation of inorganic antimony in environmental and biological samples

Abstract

A new method for the determination of inorganic Sb species by on-line cloud point extraction combined with electrothermal vaporization inductively coupled plasma atomic emission spectrometry (ETV-ICP-AES) is presented and evaluated. The method is based on the complexation of Sb(III) with pyrrolidine dithiocarbamate (PDC) which form an hydrophobic complex at pH 5.5 and subsequently enter surfactant-rich phase at pH 5.5, whereas Sb(V) remained in aqueous solutions. The preconcentration step is mediated by micelles of the non-ionic surfactant Triton X-114 with ammonium pyrrolidine dithiocarbamate (APDC). The micellar system containing the complex was loaded into the FIA manifold at a flow rate of 2.5 mL min −1, and the surfactant-rich phase was retained in a microcolumn packed with absorbent cotton, at pH 5.5. After the surfactant-rich phase was eluted with 100 μL acetonitrile, it was determined by ETV-ICP-AES. Sb(V) is reduced to Sb(III) by l-cysteine prior to determined total Sb, and its assay is based on subtracting Sb(III) from total antimony. The main factors affecting separation/preconcentration and the vaporization behavior of analyte in graphite tube were investigated in detail. Under the optimized conditions, the precision relative standard deviation (R.S.D.) for eight replicate measurements of 0.2 μg mL −1 Sb(III) was 4.3%. The apparent concentration factor, which is defined as the concentration ratio of the analyte in the final diluted surfactant-rich extract ready for ETV-ICP-AES detection and in the initial solution, was 872 for Sb(III). The limit of detection (LOD) for Sb(III) was 0.09 μg L −1. The proposed method was successfully applied for the speciation of inorganic antimony in different water samples and urine sample with satisfactory results.