Abstract

Hydrophobic deep eutectic solvents (DESs), formulated with menthol and medium-chain fatty acids, exhibit restricted sensitivity for paraben extraction through liquid–liquid microextraction. Consequently, to enhance the effectiveness of the DES-based dispersive liquid–liquid microextraction (DES-DLLME) technique, we aimed to explore the effects of varying fatty acid chain lengths and refining the menthol-to-fatty acid molar ratios. In this study, an optimized DES-based DLLME strategy was developed to extract four parabens, methylparaben, ethylparaben, propylparaben, and butylparaben, which were subsequently analyzed using high-performance liquid chromatography with diode array detection (HPLC-DAD). After optimization, the developed DES-DLLME demonstrated good linearity in the concentration range of 0.497 ng mL⁻¹ to 3.2 μg mL⁻¹ for MP, 0.467 ng mL⁻¹ to 3.2 μg mL⁻¹ for EP, 0.416 ng mL⁻¹ to 3.2 μg mL⁻¹ for PP and 0.402 ng mL⁻¹ to 3.2 μg mL⁻¹ for BP. The limits of detection and quantification were in the ranges of 0.121–0.149 ng mL⁻¹ and 0.402–0.497 ng mL⁻¹, respectively. Good reproducibility (RSD < 4.92%, n = 6) and precision (RSD < 3.32%, n = 5) were obtained. This method exhibited promising application potential in the analysis of the four parabens in both labeled and unlabeled mouthwash samples, with good recoveries in the range of 85.01 ± 3.17% to 104.42 ± 2.36%. The proposed DES-DLLME method is eco-friendly, simple, low-cost, rapid for extraction (50 s), and utilizes a small volume of the extracting solvent (900 µL). The optimized DES-DLLME method provided an efficient and sustainable solution for the analysis of parabens in mouthwashes, highlighting its applicability in eco-friendly analytical practices.