Novel low viscous hydrophobic deep eutectic solvents liquid-liquid microextraction combined with acid base induction for the determination of phthalate esters in the packed milk samples

Abstract A quick and simple sample extraction method was demonstrated for the liquid-liquid microextraction of seven phthalate acid esters (PAEs) using acid-base induced deep eutectic solvent (DES) with vortex-mixing assistance. The binary and ternary DESs were prepared by a range of fatty acids (C8-C12) and menthol, which ones act as hydrogen bond donors and acceptors respectively. Fatty acids and menthol served as an extraction solvent and a pH-dependent phase based on the acid-base reaction caused by the adjustment of the pH of the solution. Additionally, the extraction efficiency of the deep eutectic solvent (DES) was improved by adding the emulsifier sodium hydroxide. Hydrochloric acid was used as a phase separation agent. Additionally, the key parameters were optimized through orthogonal array experimental design and statistical analysis. Under the optimal extraction conditions, good linearity of the method was obtained in the concentration range from 1 to100 μg mL-1 for phthalate esters, and preconcentration was completed within 5 min. The limits of detection (LODs) was 1.06 - 4.55 ng mL-1, respectively. The spiked recovery values of actual samples were in the range of 83.9% – 107.0% with relative standard deviations (RSDs) of 1.63–4.44%. The quantification limits of the seven phthalates were 3.20 to 13.61 ng mL-1.Thus, the overall experimental results revealed the promise of deep eutectic solvent (DES) for support in determining phthalate acid esters (PAEs). Therefore, this method could be used for the determination of seven phthalate acid esters in packaged milk samples.