In this study, a method for the determination of low concentrations of lead in beer samples using solid-phase extraction with a flow injection analysis system and detection by flame atomic absorption spectrometry (FAAS) was developed. Moringa oleifera seeds were used as a biosorbent material. Chemical and flow variables of the online preconcentration system, such as sample pH, preconcentration flow rate, eluent flow rate, eluent concentration, particle size, and sorbent mass, were studied. The optimum extraction conditions were obtained using a sample pH of 6.0, sample flow rate of 6.0 mL min−1, 63.0 mg of sorbent mass, and 2.0 mol L−1 HNO3 at a flow rate of 2.0 mL min−1 as the eluent. With the optimized conditions, the preconcentration factor, precision, detection limit, consumption index, and sample throughput were estimated as 93, 0.3% (10.0 μg L−1, n = 7), 7.5 μg L−1, 0.11 mL, and 23 samples per hour, respectively. The method developed was successfully applied to beer samples and recovery tests, with recovery ranging from 80% to 100%.
This paper reports a method for the determination of zinc in Brazilian sugar cane spirit, (cachaça in Portuguese), using solid-phase extraction with a flow injection analysis system and detection by FAAS. The sorbent material used was activated carbon obtained from Moringa oleifera husks. Flow and chemical variables of the proposed system were optimized through multivariate designs. The factors selected were sorbent mass, sample pH, sample flow rate, and eluent concentration. The optimum extraction conditions were obtained using a sample pH of 4.0, a sample flow rate of 6.0 mL min−1, 30.0 mg of sorbent mass, and 1.0 mol L−1 HNO3 as the eluent at a flow rate of 4.0 mL min−1. The limit of detection for zinc was 1.9 μg L−1, and the precision was below 0.82% (20.0 μg L−1, n = 7). The analytical curve was linear from 2 to 50 μg L−1, with a correlation coefficient of 0.9996. The method developed was successfully applied to spiked Brazilian sugar cane spirit, and accuracy was assessed through recovery tests, with results ranging from 83% to 100%.
Arsenic contamination is worrisome in mineral exploration regions. Efficient arsenic monitoring is dependent on detectability at trace level in environmental matrices. This paper presents a procedure to evaluate the occurrence of arsenic in environmental sediment and water samples collected from a mining area in Catalão, Goiás State (GO), Brazil. The water and sediment samples were analyzed by graphite furnace atomic absorption spectrometry (GF AAS) after appropriate chemical treatment. For the arsenic determination, analytical performance was improved employing multivariate tools. The instrumental conditions were optimized using a 23 factorial design and the response surface methodology (RSM) was applied with a central composite design (CCD). Iridium was used as a permanent modifier. The results for the sediment samples showed arsenic concentrations below the threshold for adverse effects ranging from 2.06 to 3.82 mg Kg-1. The concentrations in water samples were below LOD. The LOD and LOQ were, respectively, 0.33 and 1.09 µg L-1 to water and digested sediment samples. Under the optimal conditions, the dynamic working range was linear of LOQ to 50.0 µg L-1. The method was applied to determine concentrations of arsenic in water and sediments collected from mining sites, which can be used to assess the availability of arsenic in the region.
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