Nonionic surfactants based hydrophobic deep eutectic solvents for liquid-liquid microextraction of Sudan dyes in tomato chili sauces.

Abstract A new type of high-density hydrophobic deep eutectic solvents (DESs) were synthesized with nonionic surfactants as hydrogen bond acceptors and hexafluoroisopropanol (HFIP) as hydrogen bond donor. Brij-35 was selected as the optimal nonionic surfactant for the preparation of Brij-35-HFIP-DES (molar ratio 1:20). A vortex-assisted DES-based liquid–liquid microextraction method was proposed for determination of Sudan dyes in tomato chili sauces. The whole pretreatment process only needs 5 min and 1.1 mL of organic solvent. The method with HPLC-DAD shows high efficiency (enrichment factors 89–176 and extraction rates 61.0–74.6%) and good performance with linearity (R ≥ 0.9997) in 0.04–2 μg g−1 range, detection limits of 0.0045–0.0118 μg g−1, recoveries of 91.6–104.5% and intra-/inter-day precision below 8.0%. A “DES in water in DES” aggregate microstructure was observed in DES-rich phase. The proposed method is simple, quick, eco-friendly, and suits for the efficient extraction and accurate determination of Sudan dyes in tomato chili sauces.