RESUMO
In this study, an efficient, green, and rapid sample preparation method based on mandelic acid dimer was proposed for the extraction of Cu(II) and Cd(II) from soil samples followed by flame atomic absorption spectrometry. In this research, for the first time, the liquid dimer was prepared by heating solid mandelic acid. Then the mixture of soil and a complexing agent was added into it. The mixture was transferred into a microwave oven. Diluted nitric acid solution as a dilution solvent was added. After centrifugation, two aliquots of the collected phase were removed and injected into the instrument. The relevant optimization parameters such as dimer volume, microwave exposure time, amount of complexing agent, and the type and volume of dilution solvent were investigated and optimized. Under the optimum conditions, detection limits were obtained 0.17 and 0.16 mg Kg-1 for Cu(II) and Cd(II), respectively. The linear ranges were 0.50-50 mg Kg-1 with coefficient of determination ≥ 0.9981. The developed method along with a reference method was applied for the analysis of the selected heavy metal ions in different soil samples and comparable results were obtained. Also, the method was performed on a certified reference material and the obtained concentrations compared with the certificated concentrations to assess accuracy of the proposed method.
RESUMO
In this study, a new pH-induced dispersive solid-phase extraction method using folic acid has been proposed for the extraction of Cu(II) and Pb(II) ions from water and fruit juice samples. For this purpose, at first, a specified amount of folic acid was dissolved in the sample solution containing the studied ions at pH 8.5. Then, by decreasing pH of the solution, solubility of folic acid reduced and its fine particles containing the analytes were produced. They were separated and dissolved in dimethylformamide. For more preconcentration, the developed procedure was combined with a dispersive liquid-liquid microextraction procedure. Finally, the extracted and enriched analytes were determined by flame atomic absorption spectrometry. The effect of important parameters on the extraction efficiency of the method such as pH, folic acid amount, the amount of complexing agent, dimethylformamide volume, ionic strength, and centrifugation conditions were studied. Under optimized conditions, the developed method showed linear ranges of 0.20-40 and 0.25-40 µg L-1 for Pb(II) and Cu(II) ions, respectively. Limits of detection of Pb(II) and Cu(II) were 0.07 and 0.08 µg L-1, respectively. The relative standard deviations (intra- and inter-day precisions) were between 3.8 and 5.4%. Accuracy of the proposed method was studied by determination of the analytes concentrations in a certified reference material; SPS-WW2 Batch 108. Efficiency of the proposed procedure was evaluated by analyzing Pb(II) and Cu(II) ions in various water and fruit juice samples.
