Deep eutectic solvent-based ultrasound-assisted extraction in soil samples preparation and elemental determination by ICP-OES

A fast, simple and green method was established for the extraction of Al, Be, Ca, Co, Cr, Cu, Mn, P, Pb, V and Zn from soil samples using ultrasound-assisted deep eutectic solvents (DESs). DESs based on choline chloride, carboxylic acids and polyols were investigated. It was established that the solvent synthesized from choline chloride and oxalic acid provided the highest extraction recovery (85–104%). Inductively coupled plasma-optical emission spectrometry (ICP-OES) was employed to determine the target analytes in the extracts. The parameters that affect the extraction of target analytes was optimized using standard reference samples. Target analytes could be effectively isolated from soil samples using 0.5 g of DES, ultrasound for 40 min, and heating at 80 ℃. The content of the target analytes determined by this method showed no significant difference from the certified values of 24 reference samples. The proposed method was applied to quantify target analytes in real soil samples. Compared to the traditional acid digestion method, this method showed no significant difference in precision and accuracy, with a confidence level of 95%. The proposed method was found to be simple, accurate and environmentally friendly.