Inorganic selenium speciation in water and biological samples by three phase hollow fiber-based liquid phase microextraction coupled with HPLC-UV

Abstract

A rapid, sensitive, high clean-up and economic three phase hollow fiber liquid phase microextraction method followed by HPLC-UV was applied for speciation of inorganic selenium in water and biological samples. The most sensitive absorption line at 332 nm was used for all determinations. Selenium(IV) was reacted with o-phenylenediamine to form piazselenol in an acidic medium (pH = 2). Subsequently the piazselenol complex was extracted into 20 μL of n-dodecane in the pores of the hollow fibers (membrane solvent), and then into the methanol that fills the lumen of the hollow fibers. After separation, preconcentrated Se(IV) in the organic phase was determined using HPLC-UV. Total inorganic selenium was obtained by reduction of Se(VI) to Se(IV) with hydrochloric acid. Then the concentration of Se(VI) was calculated by subtracting the concentration of Se(IV) from the total inorganic selenium concentration. The parameters that could have an effect on extraction, including pH, amount of complex reagent, HF length, extraction time, salt concentration and stirring rate, were optimized by using the one variable at a time method and central composite design. Under optimum conditions, a linear range of 0.05–200 μg L⁻¹ (R² > 0.998), a limit of detection (S/N = 3) of 0.02 and a preconcentration factor of 195 with a relative standard deviation of 5.1% were achieved. The proposed method was successfully applied to the speciation of inorganic selenium in different water and biological samples with recoveries of 95–103% for spiked samples.