Dispersive Liquid-Liquid Microextraction-Solidified Floating Organic Drop Combined with Spectrophotometry for the Speciation and Determination of Ultratrace Amounts of Selenium

In this study a simple and inexpensive dispersive liquid-liquid microextraction-solidified floating organic drop (DLLME-SFOD) has been reported for the separation and speciation of inorganic selenium prior to its spectrophotometric determination. The method is based on the formation of a yellow piazselenol complex between the Se(IV) and 3,3'-diaminobenzidine (DAB) followed by its extraction into 1-undecanol and the measurement of its absorption at 434 nm. Total inorganic selenium is determined after the reduction of Se(VI) to Se(IV). The concentration of Se(VI) is calculated by the difference between the total selenium and Se(IV). Under the optimized conditions, an enrichment factor of 133, a detection limit of 1.6 mu g L-1, a relative standard deviation of 2.1% at 50.0 mu g L-1 (n = 6) and a linear dynamic range of 5.0-600.0 mu g L-1 for the preconcentration of 20.0 mL of aqueous sample was obtained. The method was successfully applied to the determination of selenium in garlic, selenium plus tablet and water samples. The accuracy was evaluated through the recovery experiments and the analysis of a certified water sample.