ANÁLISE POR INJEÇÃO SEQUENCIAL COM DETECÇÃO POR VOLTAMETRIA DE ONDA QUADRADA PARA DETERMINAÇÃO DE As(III) EM AMOSTRAS DE ÁGUAS USANDO ELETRODO DE OURO

A sequential injection method with square wave anodic stripping voltammetry (SI-SWASV) using screen printed and crystalline gold electrode was developed for determination of As(III). The carrier solution used for electrode conditioning and stripping medium was composed of 0.050 mol L-1 HCl, whereas the supporting electrode for samples (deposition medium) was 0.50 mol L-1 HCl. The limits of detection and quantification were 20 and 70 nmol L-1 (1.5 and 5.2 µg L-1), respectively. This limit of quantification is almost two times lower than the maximum concentration of As(III) allowed in waters by World Health Organization (10 µg L-1). The sampling throughput was 20 analyses per hour using a sample volume of 1500 µL, pumped through the flow cell at the flow rate of 15 µL s-1. Screen printed gold electrodes were not suitable for work with 0.50 mol L-1 HCl because the results were strongly dependent on the lot of sensors. Crystalline gold electrodes provided reproducible results and the method was applied for determination of As(III) in river water samples. The accuracy was evaluated by recovery studies and analyses by Graphite Furnace Atomic Absorption Spectrometry, providing recoveries between 95 and 108%.