A green deep eutectic solvents microextraction coupled with acid-base induction for extraction of trace phenolic compounds in large volume water samples

A simple, effective and convenient method for determination of phenolic compounds by acid-base induced deep eutectic solvents (DESs) microextraction was developed. The binary and ternary DESs were prepared by a range of fatty acids (C8-C12), which can act as hydrogen bond donors and hydrogen bond acceptors simultaneously. The gas-assisted mixing customization provides excellent mixing performance and concentration efficiency through the bubble adsorption mechanism for the handling of large-volume aqueous sample. In extraction process, NH3·H2O can act as the emulsifier agent and reacted with DESs to form salts with a cloudy solution, which can obviously improve the extraction efficiency. HCl can act as the phase separation agent, and there is no need to centrifuge, which increases the efficiency of analysis procedure. The factors affected on extraction efficiency were carefully optimized. At optimum conditions and molar ratio of C8:C9:C12 (3:2:1), the limit of detections (LODs), the preconcentration factor, the repeatability (RSDs%) were in the range of 0.22–0.53 μg L−1, 235–244, and 2.6–6.7%, respectively. Finally, the proposed method was applied to analyze four phenolic compounds in real water samples and the recoveries were between 87.4% and 106.6%.