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

Abstract

publicado na web em 8/11/2017 SEQUENTIAL INJECTION ANALYSIS WITH SQUARE WAVE VOLTAMMETRY DETECTION AT GOLD ELECTRODE FOR DETERMINATION OF As(III) IN WATER SAMPLES.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 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%.Keywords: sequential injection analysis; square wave voltammetry; gold electrodes; arsenic; waters. INTRODUÇÃOEm ambientes aquáticos o arsênio pode ocorrer nos estados de oxidação +3 e +5 nas formas inorgânicas de AsO 33-e AsO 4 3-, ou na forma de compostos orgânicos.1 Compostos de arsênio têm recebido atenção especial devido aos riscos de contaminação de ambientes aquáticos, sendo que seus compostos trivalentes são cerca de 60 vezes mais tóxicos do que os pentavalentes. Além disso, os compostos inorgânicos são mais tóxicos do que os orgânicos, sendo que todos eles promovem efeitos carcinogênicos. A principal rota de intoxicação humana é o consumo de água contaminada, especialmente de água subterrânea, resultando em doenças de pele, bexiga, câncer de pulmão, problemas reprodutivos e de desenvolvimento, doenças cardiovasculares, etc. Em função dessa problemática, As é considerado um poluente prioritário pela Agência de Proteção Ambiental dos Estados Unidos (US-EPA), de modo que sua monitoração em águas é essencial para evitar problemas de saúde pública, como ocorridos em Bangladesh.1,2 Para determinação de As(III), as técnicas mais comumente utilizadas são a espectrometria de massas com plasma indutivamente acoplado (ICP-MS), a espectrometria de fluorescência atômica e a espectrometria de absorção atômica. A atomização pode ser realizada em forno de grafite ou por geração de hidretos, sendo essas duas últimas capazes de promover a separação do analito da matriz, reduzindo o efeito de vários interferentes.3 Essas técnicas podem ser acopladas a cromatografia líquida de alta eficiência para fins de especiação.3 Apesar de fornecerem alta sensibilidade e baixos limites de detecção, tais técnicas têm alto custo de instrumentação e ma...

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