This work reports a study on the evaluation of extraction induced by emulsion breaking (EIEB) for Ni and V extraction from crude oil. Graphite furnace atomic absorption spectrometry (GF AAS) was employed for the determination of the analytes in the extracts. The extraction procedure was based on the preparation of oil-in-water emulsions, by mixing the crude oil with the aqueous extractant solution containing HNO 3 and Triton X-114 as surfactant, which were subsequently broken by heating. After emulsion breaking, two phases were formed: a top phase containing the original crude oil sample and a bottom phase, which was the aqueous extract containing the extracted Ni and V. The aqueous phase was collected, appropriately diluted, and analyzed by GF AAS for the determination of Ni and V in the extracts and subsequent calculation of extraction efficiency. The extraction procedure was first studied using water-in-ol emulsion; the best extraction conditions were achieved with 2.5 g of sample (about 3 mL) emulsified in 1 mL of extraction solution containing 6.5 mol L −1 of nitric acid and 20% (m/v) of Triton X-114. However, the extraction efficiency was only about 10% for Ni and V. The influence of the sample/ extractant volume ratio showed that sample volume lower than 3 mL resulted in higher extraction efficiency for both analytes, highlighting the use of oil-in-water emulsion to increase Ni and V extraction efficiency. Maximum extraction of Ni and V was obtained when the crude oil (approximately 0.3 g) was diluted with 2.5 mL of mineral oil free of metals. The diluted sample was emulsified by vigorous manual agitation with 3 mL of an extractant solution containing 20% (m/v) Triton X-114 and 6.5 mol L −1 HNO 3 . The emulsion breaking was induced by heating at 90 °C for 40 min, followed by centrifugation at 5000 rpm for 15 min. The EIEB procedure was applied to five crude oil samples, and the extraction efficiency was accessed from the total concentration of Ni and V in the samples determined by direct analysis by GF AAS and ICP-MS. The optimized EIEB procedure provided extraction of 82−103% of the Ni contained in the tested samples and 50−74% of the V.

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In this work, a separation/preconcentration method is proposed for the determination of Cd(II) and Pb(II) in swimming pool waters, using ammonium pyrrolidine dithiocarbamate (APDC) as a complexing agent and unloaded polyurethane foam (PUF) as a sorbent. The proposed method was optimized, and the defined optimal conditions were a pH of 7, 30 min of shaking time, 400 mg of PUF, and 0.5% (m/v) of the APDC solution. The release of Cd(II) and Pb(II) from the solid phase was achieved through the total digestion of PUF using a microwave-assisted acid approach with a 10.5 mol·L−1 HNO3 solution. The methodology was applied to four samples of swimming pool water for the determination of Cd(II) and Pb(II) using graphite furnace atomic absorption spectrometry (GF AAS). The limits of detection and quantification obtained were 0.02 and 0.06 μg·L−1 for Cd(II) and 0.5 e 1.8 μg·L−1 for Pb(II), respectively. We analyzed four samples of swimming pool waters, finding Cd concentrations between 0.22 and 1.37 μg·L−1. On the other hand, only one sample presented Pb concentration above the limit of quantification (11.4 μg·L−1). Recovery tests were performed by spiking the samples with known concentrations of the analytes, and recovery percentages between 82% and 105% were obtained.