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

摘要

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 NaBH_4 and 0.2 mol L~(-1) of HC1, and total arsenic using 5% w/v of NaBH_4 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.