Internal standardization for the determination of cadmium,cobalt, chromium and manganese in saline produced water from petroleum industry by inductively coupled plasma optical emission spectrometry after cloud point extraction |
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Authors: | Marcos Almeida Bezerra Sérgio Mitihiro do Nascimento Maêda Eliane Padua Oliveira Maria de Fátima Batista de Carvalho Ricardo Erthal Santelli |
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Institution: | 1. Departamento de Geoquímica, Universidade Federal Fluminense, Outeiro São João Batista s/n, Centro, Niterói/RJ, 24020-150, Brazil;2. Universidade Estadual do Sudoeste da Bahia, Departamento de Química e Exatas, Rua José Moreira Sobrinho s/n, Jequiezinho, Jequié/BA, 45206-190, Brazil;3. Centro de Pesquisas e Desenvolvimento da PETROBRAS, Avaliação e Monitoramento Ambiental, Av. Jequitibá, 950, Cidade Universitária, Rio de Janeiro/RJ, 21941-598, Brazil |
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Abstract: | In the present paper a procedure is proposed for the determination of traces of Cd, Co, Mn and Cr in petroleum industry produced water by inductively coupled plasma optical emission spectrometry. The procedure is based on cloud point extraction of these metals, as their dithizonate complexes, into the surfactant-rich phase of octylphenoxypolyethoxyethanol surfactant (Triton X-114). Extractions were carried out in solutions with salinities between 10‰ and 70‰. Since residual salinity in the surfactant-rich phase caused differences in its transport to the plasma, yttrium was used as an internal standard to correct for this effect. The simultaneous metal extraction procedure was optimized by response surface methodology using a Doehlert design and desirability function. Enhancement factors of 21, 21, 9 and 19, along with limits of quantification of 0.093, 0.20, 0.73 and 1.2 μg L− 1, and precision expressed as relative standard deviation (n = 8, 20.0 μg L− 1) of 5.8, 1.2, 1.7 and 5.7% were obtained for Cd, Co, Mn and Cr, respectively. The accuracy was evaluated by spike recovery tests on the high salinity water samples with salinity of 40 and 63‰. |
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Keywords: | Cloud point extraction Internal standard Petroleum produced water Trace metals Doehlert design |
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