Speciation of As in environmental samples using the nano-TiO₂/PCHG-FAAS online system

ABSTRACT

This work presents an alternative method for arsenic speciation using the nano-TiO₂ hydride generation photocatalytic hydride generation (PCHG) system, which is easily separated from the medium. Nano-TiO₂ was studied as photocatalyst to reduction of arsenic species by UV-induced with formic acid and atomic absorption detection of different forms of arsenic [As (III), As (V), dimethylarsinic acid (DMA)] in environmental samples (water, sediment and plant). The effect of the average pH, the organic acid concentration, the ultraviolet irradiation time and their amount were investigated. With the presence of formic acid, the process was more effective in the reduction of arsenic when compared to other organic acids, mainly acetic acid. In addition, the photocatalytic hydride generation and flame atomic absorption spectrometry (nano-TiO₂/PCHG-FAAS) increased the identification and quantification of different arsenic species. The ultrasound extraction procedure was used as a method to prepare samples with solutions of 1.0 mol L⁻¹ phosphoric acid. The accuracy of the measurements (n = 12), calculated as relative standard deviation, was less than 8.6%. The detection limits for As (III) and As (total) in samples were 0.418 and 0.574 μg g⁻¹, respectively.

KEYWORDS:

• Environmental samples and arsenic speciation
• Nano-TiO₂/UV
• photocatalytic hydride generation (PCHG)

Funding

The authors are thankful to Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) and Fundação de Amparo a Pesquisa do Estado de Minas Gerais (FAPEMIG) for financial support, and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) the fellowship to B.S.P.