Ultrasensitive Fluorimetric Detection of Trace Se(IV) as 4,5‐Benzopiazselenol on Nonpolar Adsorbents

A method for separating Se(IV) from Se(VI) has been proposed. The method is based on the formation of fluorescent 4,5‐benzopiazselenol (a complex of Se(IV) with 2,3‐diaminonaphthalene), which was quantitatively extracted in dynamic mode from aqueous solutions using glass preconcentrating cartridges filled with nonpolar adsorbents: SiO 2 ‐C8, SiO 2 ‐C16, SiO 2 ‐C18, and SiO 2 ‐HPh. The increase in the fluorescence intensity of the adsorbent in the preconcentrating cartridge with increasing concentration of 4,5‐benzopiazselenol on its surface was used to develop a method for the solid‐phase extraction (SPE)‐fluorimetric determination of Se(IV) with a detection limit of 2 ng per 0.025 g of SiO 2 ‐С16 adsorbent. When using 10 mL of solution, the detection limit was 0.2 ng mL −1 (0.2 μg L −1 ), and when using 100 mL of solution, it was 0.02 ng mL −1 (0.02 μg L −1 ). The linearity of the calibration graph was maintained up to 2 μg per 0.025 g when using the SiO 2 ‐C16 adsorbent. Se(VI) did not form a complex with diaminonaphthalene and was not extracted by nonpolar adsorbents. Se(VI) passing through the preconcentrating cartridge can be determined in the effluent by ICP‐MS.