Abstract
Arsenic is a well-known environmental contaminant that can be arisen from natural sources and anthropogenic activities. Because inorganic arsenic is present in environment at trace level and its toxicity is reported highly dependent on the chemical forms, it is important to develop a sensitive and selective method for the study of inorganic arsenic species in aqueous samples. To this aim, HPLC coupled with hydride generation (HG) is the most popular sample separation and derivatization method for the determination of inorganic arsenic species. Recently, nano-TiO2 has become an emerging and environmental friendly material for the facilitation of photo-catalytic reaction. However, until now, only few reports regarding the physicochemical study on the reduction of arsenic species by the photo-catalytic character of TiO2 presented in the literature. Toward the goals of developing a high efficient and green method for arsenic speciation, with the aid of pre-reductant, Na2S2O4, we utilized a poly(methyl methacrylate) (PMMA) chip-base photo-reactor coated with AuNPs/TiO2 nano-composites as an interfacing device to combine HPLC and ICP-MS together. To convert inorganic arsenic species to gaseous products, we loaded AuNPs onto TiO2 surface to improve the energtics of the nano-composites and increase the efficiency of the interfacial charge-transfer process. Meanwhile, we also developed a physical method to attain a low cost, simple, rapid and room temperature process for the immobilization of nano-composites onto the channel surface of chip. Under the optimized conditions, the limit of detection (LOD) of As(III) and As(V) were 0.23 and 0.33 μg L-1, respectively. Validation of the proposed method was performed by analyzing NIST SRM 1643e. Based on our experimental results, we have successfully developed a new method for the determination of inorganic arsenic species in water sample. It also indicated that our developed on-line system is a sensitive, stable, low cost and geener method. To the best of our knowledge, this is the first approach using AuNPs/TiO2 photo-catalytic reduction system for the determination of inorganic arsenic species in natural water.