A miniaturized UV-LED array chip-based photochemical vapor generator coupled with a point discharge optical emission spectrometer for the determination of trace selenium

Abstract

An ultraviolet light emitting diode (UV-LED) array chip as the irradiation source for nano-TiO₂ catalyzed photochemical vapor generation (PCVG) was combined with a hollow electrode point discharge microplasma optical emission spectrometer (HEPD-OES) to realize instrumental miniaturization, and utilized for quantitative analysis of trace selenium (Se). Under the irradiation of the UV-LED array chip, Se(IV) and Se(VI) could be effectively converted into volatile species in a miniature quartz coil coating with nano-TiO₂ on its inner wall as a photocatalyst. Meanwhile, volatile analyte species were totally guided into the hollow electrode and transported into the inside of micro-discharge plasma for excitation and enhanced sensitivity. Experimental conditions of PCVG and HEPD-OES were investigated in detail using an analytical line of Se at 203.98 nm through the peak area integrated for quantitation. Under optimized experimental conditions of 0.6 mL sample volume, 10% (v/v) acetic acid, 370 nm and 50 W LED, and 75 s UV irradiation, Se(IV) and Se(VI) could be detected with the same LODs, 3.9 μg L⁻¹ and 4.1 μg L⁻¹, respectively. The accuracy of the proposed method was validated by the analysis of the Certified Reference Materials (CRMs, GBW(E)080395 and BWB2427-2016) and real water samples. With the advantages of high compatibility, high efficiency, small size and low power consumption, the integration of UV-LED array chip based PCVG and HEPD-OES would be beneficial to fabricate miniaturized and portable devices for field analysis.