Abstract
The trace element selenium (Se) is essential for human health. Dietary Se intake levels mainly depend on the total concentration and bioavailability of Se in food sources, which depend on the multiple factors such as Se content of soils and irrigation water. Generally, the predominant forms of Se in environment are selenite (i.e., Se(IV)) and selenate (i.e., Se(VI)), with Se(VI) be considered more harmful to aquatic invertebrates and fish than Se(IV). Hence, the speciation of inorganic Se species in the environmental water samples is extremely desirable. Because the concentration of Se species in typical environmental samples can be as low as sub μg L─1, high sensitivity and selectivity are necessary requirements for the development of a suitable analytical technique. In this study, we developed a chip-based vapor generation (VG) system to interface chromatographic separation with inductively coupled plasma-mass spectrometry for the determination of inorganic selenium species (i.e., Se(IV) and Se(VI)). The chip-based VG system consisted of a burgeoning photocatalyst graphene─titanium dioxide (GR─TiO2) nanocomposite and a poly (methyl methacrylate) (PMMA)-based photocatalyst-assisted reduction device (PMMA-based PCARD). Because the used nanocomposite possessed extended light absorption ability and greater charge separation efficiency, efficient conversion of Se(IV) and Se(VI) into volatile species was expected. Under the optimized condition, it merely needed 15s to transform inorganic selenium into gaseous selenide. The limit of detection of Se(IV) and Se(VI) were 3.9 and 2.4 ng L─1, respectively. Based on the analytical results, the proposed hyphenated system was proven to be a promising platform for online determination of inorganic selenium species.