Antimony is a cumulative toxic element with no known biological function and its physicochemical and toxic properties depend on its binding form and oxidation state. All this information emphasizes the importance of identifying and quantifying the chemical forms of antimony to provide comprehensive information about its toxicity and environmental relevance. In the aqueous environment, inorganic antimony mainly appears in the oxidation states +V and +III. In natural, non-contaminated waters, extremely low concentrations of total antimony are usually quantified. Direct speciation analysis, in this case, is practically impossible. So, many of the procedures for the selective separation/preconcentration and quantification of antimony species in natural waters are based on the coupling of a selective separation technique with a sensitive detection method.

During the past years, separations and preconcentrations based on cloud point extraction (CPE) are becoming an important and practical application of the use of surfactants in analytical chemistry. The technique is based on the property of most non-ionic surfactants in aqueous solutions to form micelles and become turbid when heated to the cloud point temperature (CPT). Above the CPT, the micellar solution separates in a surfactant-rich phase of a small volume and in a diluted aqueous phase, in which the surfactant concentration is close to the critical micellar concentration (CMC). Any analyte solubilized in the hydrophobic core of the micelles, will separate and become concentrated in the small volume of the surfactant-rich phase. Metallic elements can be extracted to the surfactant-rich phase, trapped in the hydrophobic micellar core, in the form of hydrophobic complexes that are formed between the metal ion and an appropriate chelating agent under adequate conditions.

The aim of the present work is to use an optimized CPE procedure for the selective separation/preconcentration of Sb(III) prior to its quantification by electrothermal atomic absorption spectrometry (ETAAS). In this procedure, ammonium pyrrolidine dithiocarbamate (APDC) is used as the chelating agent and Triton X-114 (TX-114) as the extracting one. Potential factors affecting the CPE separation/preconcentration of Sb(III) are investigated in detail. A certified reference material for trace elements in riverine water SLRS-4 is used for checking the accuracy of the method for the total antimony determination after reduction of Sb(V) to Sb(III). Finally, the method is applied to the speciation of inorganic antimony in non-contaminated natural waters (well and lake waters).

The work was supported by the Scientific Grant Agency of the Slovak Republic Ministry of Education and the Slovak Academy of Sciences under contract Nos. VEGA 1/0153/17, 1/0164/17, 1/0146/18, 1/0354/19 and 1/0390/19.