Abstract

A simple and fast anodic voltammetric method was employed to determine traces of As(III) in urine samples using commercial screen-printed graphene electrodes without subsequent modification. To obtain a sensitive and selective method for As(III) determination, the effects of various parameters such as pH, supporting electrolyte concentration, accumulation potential (E-acc), accumulation time (t(acc)), and potential scan conditions were studied. The optimum experimental conditions were chosen to be as follows: pH of 2.8 (0.01 mol L-1 phosphate buffer), scan increment of 4 mV, pulse width of 80 ms, pulse period of 0.5 s, and pulse amplitude of 200 mV. Differential pulse voltammograms were obtained by scanning from -0.80 V to 0.80 V without applying an accumulation step. Under these conditions, one peak was observed at 0.27 V due to As-0 oxidation. After optimizing the experimental conditions, the anodic peak current for As was found to be linearly related to its concentration up to ca. 5.0 mu g L-1, with detection and quantitation limits (DLs, QLs) of 0.28 mu g L-1 and 0.92 mu g L-1, respectively. The developed method was validated by the determination of As(III) in spiked tap water from our laboratory, which showed an As(III) concentration of 50.64 +/- 0.10 mu g L-1 (spiked with 50.0 mu g L-1); two urine samples (where As was not detected) spiked with As(III) 0.73 mu g L-1 and 0.91 mu g L-1 (in the cell) showed an As(III) concentration of 0.70 mu g L-1 and 0.91 mu g L-1, respectively. The method was successfully applied to the determination of As-total in 16 urine samples obtained from workers occupationally exposed to inorganic arsenic compounds without previous treatment. The results obtained for As-total were compared with measurements made by an external analytical laboratory, which used HG-AAS. To determine As-total, As(V) was reduced in the presence of thiosulfate in an acid medium. The electrode showed good stability and repeatability.