Speciation of Chromium(VI) and Selenium(IV and VI) by High-Performance Liquid Chromatography–Fluorometric Detection Using 2,3-Diaminonaphthalene as a Single Derivatizing Reagent

Abstract

Abstract A speciation method for chromate, selenite, and selenate was developed by high-performance liquid chromatography (HPLC)–fluorometric detection (FL) using a single derivatizing reagent. Chromium(VI) was determined based on the fluorescence intensity of 1H-naphtho[2,3-d][1,2,3]triazole (NAT) derived from 2,3-diaminonaphthalene (DAN) and nitrous ion; the NO2− was generated through a redox process between Cr(VI) and hydroxylamine hydrochloride (HACl). 4,5-Benzopiazselenol (Se-DAN) was also derived from Se(IV) and DAN, and it was resolved from NAT and detected by reversed-phase HPLC–FL operated under a single setting of an excitation and a fluorescence wavelength. Linear ranges of the calibration curve and detection limits were 0–20 µmol L−1 (correction coefficient: 0.995) and 0.1 µmol L−1 for Cr(VI), and 0–20 µmol L−1 (0.995) and 0.2 µmol L−1 for Se(IV), respectively. Concentration of Se(VI) was estimated from the difference in its concentration between total Se and Se(IV). The analytical procedure for the determination of total Se included a reduction of Se(VI) to Se(IV) with hydrochloric acid and potassium bromide. The linear range of the calibration curve and detection limit for Se(VI) was 0–20 µmol L−1 (correction coefficient: 0.990) and 0.3 µmol L−1, respectively. The proposed method was applied to the determinations of Cr(VI), Se(IV), and Se(VI) in a river water sample. Recoveries of Cr and Se species ranged between 98 and 104%, and the relative standard deviations were about 5% at 10 µmol L−1 levels of the species.