Pre-concentration and speciation of inorganic antimony in bottled water and natural water by cloud point extraction with Electrothermal Atomic Absorption Spectrometry

A method for antimony speciation by cloud point extraction (CPE) was optimized and validated in house. The pre-concentration method was based on the selective cloud point extraction of Sb(III) after its complexation with ammonium pyrrolidine dithiocarbamate (APDC) at pH 2.0, separation of a surfactant rich phase on the cloud point of the non-ionic surfactant (Triton X-114) and subsequent determination by Electrothermal Atomic Absorption Spectrometry (ET AAS). Sb(V) was not extracted at pH 2.0. Total Sb was determined after reducing Sb(V) to Sb(III) by L-cysteine. Then, concentration of Sb(V) was calculated by subtracting Sb(III) from total antimony. The main factors affecting separation/pre-concentration were investigated using univariate and multivariate approach. The detection limit for Sb(III) was 0.06 mu g L-1, the enrichment factor for this determination was 12, and the relative standard deviation (RSD) was <5.9%. The proposed method was applied for the speciation of inorganic Sb in different water samples with satisfactory results. For the first time, a case study was conducted with Brazilian mineral waters stored in PET bottles in the speciation of Sb. The results showed that Sb(III) concentrations ranged from 1.8 +/- 03 mu g L-1 to 32 +/- 0.2 mu g L-1. The Sb(V) values ranged from 0.63 +/- 0.01 mu g L-1 to 1.88 +/- 0.01 mu g L-1. (C) 2017 Elsevier B.V. All rights reserved.