Indirect spectrophotometric determination of ultra trace amounts of selenium based on dispersive liquid–liquid microextraction–solidified floating organic drop

Abstract

A novel dispersive liquid–liquid microextraction–solidified floating organic drop (DLLME–SFOD) method combined with fiber optic-linear array detection spectrophotometry has been developed for the indirect determination of selenium. The method is based on the oxidation of the I− to iodine by inorganic Se(IV). The produced I2 reacts with the excess of I− ions in acidic media to give triiodide ions. The I3- is then extracted into 1-undecanol by DLLME–SFOD upon the formation of an ion pair with cetyltrimethylammonium cation. The extracted ion pair is determined by measuring its absorption at 360nm. The absorbance signal is proportional to the selenium concentration in the aqueous phase. Under optimum conditions, the method provided an enrichment factor of 250 with a detection limit of 16.0μgL−1 and a linear dynamic range of 40.0–1000.0μgL−1. The relative standard deviation was found to be 2.1% (n=7) at 100.0μgL−1 concentration level. The method was successfully applied to the determination of selenium in water samples and selenium plus tablet.