Deep eutectic solvent-based emulsification liquid–liquid microextraction coupled with gas chromatography for the determination of thiophenols in water samples

Abstract

A simple, fast, cheap, and effective method named deep eutectic solvent-based emulsification liquid–liquid microextraction (DES-ELLME) was employed to extract thiophenols from water samples. DES was characterized by Fourier transform-infrared (FT-IR) spectroscopy, CHN elemental analysis, and proton and carbon nuclear magnetic resonance spectroscopies (¹H-NMR and ¹³C-NMR). 50 μL DES was added to the aqueous sample solution and a uniform solution was formed immediately. After injection of 50 μL acetone into this solution, turbidity was observed. Then, the phase separation (DES rich phase/aqueous phase) was performed by centrifugation. DES rich phase was subjected to gas chromatography with a flame ionization detector (GC-FID). Significant factors including the volume of acetone and DES, ultrasonication time, and pH were combined using a desirability function (DF) and optimized through a Box–Behnken design. Calibration graphs were linear in the concentration range of 0.02–100 mg L⁻¹ under optimum experimental conditions; the coefficients of correlation were more than 0.999. The limits of detection and quantification were in the ranges of 10–15 μg L⁻¹ and 33–50 μg L⁻¹, respectively. This method was used to determine target analytes in spiked water samples; the relative mean recoveries were 96 to 104%.