A novel deep eutectic solvent based on oleic acid and betaine hydrochloride for liquid-phase microextraction of Sudan IV from water and food samples

Abstract

In this study, a novel green hydrophobic deep eutectic solvent (DES) composed of oleic acid (OLC) and betaine hydrochloride (BET) was synthesized and applied for the extraction of Sudan IV dye from natural water and food samples using ultrasonic-assisted dispersive liquid-phase microextraction (UA-DLPME). In this DES system, OLC acted as the hydrogen bond donor (HBD), while BET served as the hydrogen bond acceptor (HBA). Key analytical parameters, including pH, DES molar ratio, sonication and centrifugation times, and initial and final sample volumes, were studied and optimized. The DES-UA-DLPME method exhibited a rapid and efficient extraction process, achieving equilibrium within 1 min at room temperature. The method demonstrated excellent analytical performance with a limit of detection (LOD) and limit of quantification (LOQ) of 0.75 and 2.48 µg kg⁻¹ for food samples and 0.914 and 3.047 µg L⁻¹ for water samples, respectively. The method’s preconcentration factor (PF) and enrichment factor (EF) were 40 and 35.8, respectively, with an acceptable analytical recovery (AR) of 87–104% across various matrices. The linear dynamic range (LDR) was 0.1–600 µg L⁻¹ with a correlation coefficient (R²) of 0.995. The precision of the method, expressed as relative standard deviation (RSD), was 4.9% (n = 6). Matrix effects were also studied and found to be negligible for the tested natural water and food samples in the recovery range of 87–106%. This DES-UA-DLPME approach offers a green, rapid, and highly effective method for the determination of Sudan IV dye in complex matrices.