keywords: Arsenic, assay, conductometry, inhibition, soybean, urease
This study describes a conductometric inhibition assay for the quantitative determination of arsenic ions in aqueous systems using soybean (Glycine max) urease. In this approach, the decrease in conductivity as a consequence of inhibition of urease activity by As (III) ions was evaluated and used to plot a calibration curve of %inhibition against arsenic concentration. The curve displayed linear relationship in the concentration range of 0.01 – 10 mg/L according to the regression equation 4.1427x + 41.0238 with an R2 of 99.77% which shows very good correlation. Optimization of process parameters revealed pH maxima within the range of 7.0 – 7.5 and temperature within the range of 35 – 45oC. The determination of arsenic in synthetic water samples using the proposed method was satisfactory when compared with a spectrophotometric reference method and AAS analysis. The results showed no significant difference in 80% of the evaluated samples at 95% confidence level. Repeatability (precision) of the method was 4.8% RSD for 6 measurements (0.5 mg/L). The relative accuracy of the method ranged from 73.4 – 97.85%. Limit of detection (LOD) and limit of quantitation (LOQ) were 0.043 mg/L and 0.145 mg/L, respectively. Overall, the method presented in this study shows good potential for rapid determination of arsenic in water samples.
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