Extração de arsênio assistida por ultrassom e determinação por espectrometria de absorção atômica com geração de hidretos (HG-AAS): análise de material particulado atmosférico como estudo de caso

Abstract

This study aimed to develop a method for arsenic extraction from atmospheric particulate matter samples using an ultrasonic bath, followed by quantification by hydride generation atomic absorption spectrometry (HG-AAS). Initially, the operational conditions were investigated to obtain the best instrumental performance, and the most suitable analytical figures of merit were achieved at a peristaltic pump speed of 40 rpm, an Ar carrier gas flow rate of 100 mL min-1 , a delay time of 50 s, 5.0 mol L -1 HCl, and 1.25% (m v -1 ) NaBH₄, with pre-reduction using KI and L-ascorbic acid 2.0% (m v -1 ). During the development of the sample preparation procedure, urban dust was used as a test sample and EPA Method 3050B as a reference, yielding an arsenic concentration with a relative standard deviation (RSD) below 5.0%, indicating good precision of the method employed. In this method, recoveries at the low, medium, and high levels ranged from 91 to 101%, and no matrix effect was detected under the conditions evaluated. Subsequently, the efficiency of HCl, HNO3 , and H3PO4 for arsenic extraction in combination with an ultrasonic bath was evaluated using a mixture design. Satisfactory results were obtained using HCl, a binary HNO3 -H3PO4 mixture at a 3:1 v v -1 ratio, and a ternary mixture at a 1:1:1 v v -1 ratio, with recoveries above 90%. In addition to the extracting agents, the effects of extraction time and acid concentration were also investigated, and satisfactory results were achieved using concentrated HCl for 10 min of extraction in an ultrasonic bath at 60 °C. To apply the developed method, it was used for arsenic extraction in five PM2.5 samples collected in Juiz de Fora, Minas Gerais, Brazil, using MicroVol-1100 samplers, with PM2,5 concentrations ranging from 11.9 to 64.0 µg m-3 . Daily arsenic concentrations ranged from 20.7 to 1149 ng m-3 , demonstrating the adequate applicability of the developed ultrasonic extraction method followed by HG-AAS quantification. Under the optimized conditions, a working range of 0.5 to 5.0 µg L -1 yielded limits of detection (LOD) and quantification (LOQ) of 0.12 and 0.35 µg L -1 , respectively. Thus, arsenic determination in PM₂.₅ was shown to be feasible using less extraction time, sample mass, and reagent consumption, in addition to generating less waste. The results also indicated the need for broader studies to assess arsenic levels in PM2.5 in Juiz de Fora, Minas Gerais, Brazil, their sources, and variations over different periods, given the scarcity of studies on this topic in the city.