Effective extraction of parabens from toothpaste by vortex-assisted liquid-phase microextraction based on low viscosity deep eutectic solvent

An efficient, green and reliable method, namely deep eutectic solvent-based vortex-assisted liquid-phase microextraction (DES-VALPME) was proposed for the rapid extraction and sensitive high performance liquid chromatography coupled with variable wavelength detector (HPLC-VWD) determination of methylparaben (MP), ethylparaben (EP), propylparaben (PP) and butylparaben (BP) in toothpaste samples as a proof-of-concept example of trace analysis of personal care and cosmetic products. Compared with traditional DES suffering from higher viscosity, a class of six low viscosity DESs were synthesized by simply dissolving quaternary ammonium salts (hydrogen bond acceptors, HBAs) in methanol or ethanol (hydrogen bond donors, HBDs) at ambient temperature. Initial studies indicated that the DES consisting of tetrabutylammonium chloride (TBAC) and ethanol at a molar ratio of 1:5 achieved the highest extraction efficiency for all target analytes. The influence of type, molar ratio and volume of DES, extraction temperature and vortex time on the extraction efficiency was investigated and optimized systematically. Under the selected conditions, the method displayed satisfactory linearity in the range of 0.05–10 μg/g (R 2  ≥ 0.9995), acceptable recoveries for the real samples (varied from 79.4% to 108.6%), good precision (with relative standard deviation ≤ 5.2 %), as well as lower limits of detection (in the range of 0.01–0.02 μg/g). This study demonstrates that the separation and determination of PBs with the developed DES-VALPME-HPLC-VWD technique is simple, efficient, sensitive and inexpensive.