Chiang Mai Journal of Science

Anodic stripping voltammetric (ASV) method using a screen-printed carbon electrode (SPCE) modified with gold nanoparticles and with anion exchange column preconcentration/separation was developed for determination of trace inorganic arsenic. The gold nanoparticles were in-situ electro-deposited on the SPCE while the As(III) was preconcentrated on the electrode at -500 mV versus Ag/AgCl reference electrode during a deposition step. Then, differential pulse waveform was scanned from 0 to +800 mV and a voltammogram was recorded during a stripping step. Under the optimum condition of 0.10 M HCl as an electrolyte solution, -500 mV deposition potential, 60 s deposition time, and 33.33 mV/s scan rate, a linear calibration graph in the range of 30 - 150 mg/L with a calibration slope of 0.110 mA L/mg (R2 = 0.998) was obtained. Limit of detection of 8.9 mg/L was achieved and with good precision, i.e., relative standard deviation is in the range of 0.7 - 1.3 %. In addition, anion exchange column was applied for preconcentration and separation of arsenic species which help to improve sensitivity and selectivity of the method. As(V) was retained in the column while As(III) and other interfering cations were passed through. The As(V) was then desorbed by using 0.10 M HCl and reduced to As(III) by L-cysteine before ASV determination. The proposed method was applied for determination of inorganic arsenic in soil extracted samples with satisfactory results.