Using mandelic acid as an extraction solvent in the extraction of Cu(II) and Cd(II) from soil samples

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.