Development of chip-based photocatalyst-assisted reduction device to couple high performance liquid chromatography and inductively coupled plasma-mass spectrometry for determination of inorganic selenium species

Abstract

In this study, a poly(methyl methacrylate) chip-based photocatalyst-assisted reduction device (PMMA chip-based PCARD) was developed as a reactor based on its excellent optical properties and ease of fabrication. Its transmittance of ultraviolet light at 365nm (UV365) was found to be as high as 92% using a PMMA of 2mm thickness. To optimize the vaporization efficiency, the effect of varying the depth of the geometry trenched on the PMMA-based chip was investigated. After optimization, it required only 29s of UV365 irradiation to vaporize the selenium (Se) species of interest. The PMMA-based chip was successfully used as an interfacing device for the hyphenation of high performance liquid chromatography (HPLC) separation and inductively coupled plasma-mass spectrometry (ICP-MS) detection. Additionally, under the optimized conditions for vaporization, using 1gL(-1) titanium dioxide nanoparticles (nano-TiO2) at pH 5, we found that Se(IV) and Se(VI) were converted quantitatively into volatile Se products. In addition, the optimized vaporization efficiency of the Se species of interest for the online HPLC/PMMA chip-based PCARD/ICP-MS system enabled us to achieve detection limits for Se(IV) and Se(VI) in the nanogram-per-liter range (based on 3σ). A series of validation experiments indicated that our proposed methods could be applied satisfactorily to the determination of inorganic Se species in environmental water samples.

Keywords: Chip; Inductively coupled plasma-mass spectrometry (ICP-MS); Photocatalyst; Poly(methyl methacrylate) (PMMA); Selenium (Se); Vaporization.