Optimization of an HPLC-HG-AFS method for screening Sb(v), Sb(iii), and Me3SbBr2 in water samples

Abstract

A procedure for the separation and determination of inorganic and organic species of antimony based on the use of coupled high-performance liquid chromatography (HPLC) hydride generation (HG) atomic fluorescence spectrometry (AFS) is described. Me₃SbBr₂ and inorganic Sb(V) and Sb(III) were separated on an anion-exchange column [Hamilton PRPX-100 (100 × 4.1 mm)] using the concentration gradient between potassium hydroxide, 20 mM pH 11, and ammonium tartrate, 200 mM pH 5. The flow rate through the column was 1.5 mL min⁻¹. The retention times were 0.98, 1.71 and 5.03 min for Me₃SbBr₂, Sb(V) and Sb(III), respectively. The hydrides were generated on-line with 3% m/v NaBH₄ and 2 mol l⁻¹ HNO₃ solutions. The intensity of emission was linearly related to the concentration of the derivatized Me₃SbBr₂ species in the range 1.0–50.0 µg l⁻¹ (r = 0.9996), Sb(V) species in the range 1.0–50.0 µg l⁻¹ (r = 0.9998) and Sb(III) in the range 2.5–50.0 µg l⁻¹ (r = 0.9998), with detection limits of 0.04 µg l⁻¹ for Me₃SbBr₂, 0.09 µg l⁻¹ for Sb(V) and 0.26 µg l⁻¹ for Sb(III). The precisions evaluated using the relative standard deviation (RSD) were 6.8%, 2.4% and 3.3% for Me₃SbBr₂, Sb(V) and Sb(III), respectively. The method has a sensitivity suitable for monitoring drinking and surface waters according to the regulations established by the EU directives for antimony (10 ug 1⁻¹), and it was applied to the speciation of inorganic and organic antimony in several spiked water samples. The precisions for well water, Merck and mineral water were limited in relation to Me₃SbBr₂ due to its conversion to Sb(V).