Determination of arsenic(III) and total inorganic arsenic in water samples using variable tetrahydroborate(III) and acid concentrations by continuous-flow hydride-generation atomic absorption spectrometry

Abstract

A simple procedure was developed for the direct determination of As(III) and total inorganic arsenic in water samples using continuous-flow hydride generation atomic absorption spectrometry without prereduction of As(V). Under optimized conditions, As(III) was determined using 1% w/v of NaBH₄ and 0.2 mol L⁻¹ of HCl, and total arsenic using 5% w/v of NaBH₄ and 6 mol L⁻¹ of HCl. The concentration of As(V) was determined by the difference between total inorganic arsenic and concentration of As(III). Interferences from methylated arsenic species, mutual hydride-forming, and transition elements in the determination of As(III) and total arsenic were evaluated. With the proposed procedure, detection limits of 0.1 µg L⁻¹ for As(III) and 0.25 µg L⁻¹ for total arsenic were achieved. The relative standard deviations were 2.0% for 2 µg L⁻¹ of As(III) and 3.5% for 2 µg L⁻¹ of As(V) determined as total arsenic. Spike recoveries were in the range of 91–111% for As(III) and 91–114% for As(V). The method was validated by analysing certified reference materials SRM-1640 and NASS-5. The developed methodology constitutes an economic, simple, and reliable way to determine inorganic arsenic species in natural waters and other similar samples with negligible or no content of methylated arsenic species. Speciation analysis was satisfactorily applied to different types of natural water samples.

Keywords:

• Arsenic speciation analysis
• Hydride generation atomic absorption spectrometry
• Inter-element interferences
• Natural waters

Acknowledgements

The first author thanks Mr B. M. Jha, Chairman, CGWB, Faridabad and Mr N. Varadaraj, Regional Director, CGWB, SECR, Chennai for their permission to publish this article. The authors thank the anonymous reviewers for their constructive comments.