Vortex-assisted natural deep eutectic solvent dispersive liquid-liquid microextraction based on the solidification of a floating organic drop for the determination of benzoic acid and sorbic acid in condiments.

A simple, inexpensive, reliable and environmentally friendly method based on vortex-assisted dispersive liquid-liquid microextraction combined with solidification of a floating organic drop (VA-DLLME-SFO) followed by high performance liquid chromatography with a diode array detector (HPLC-DAD) was developed to determine benzoic acid (BA) and sorbic acid (SA) in ketchup and powder bags of instant noodles. Hydrophobic natural deep eutectic solvents (NADESs), as the microextraction solvent, were prepared with ternary components. Acetic acid can reduce the viscosity of hydrophobic NADESs and vortex can promote the dispersion of NADESs in aqueous solvents. In the DLLME process, several key parameters were optimized, including the type and volume of hydrophobic NADES, pH value, vortex time and salt content. Meanwhile, these parameters were assessed using response surface methodology based on the Box-Behnken design (BBD). Under optimal conditions, the developed method showed good linearity in the selected range (r2, 0.9997). The limits of detection were 0.2 μg mL-1 and 0.07 μg mL-1 for BA and SA, respectively. Recoveries were in the range of 82.21% to 102.70% and the relative standard deviations (intra-day and inter-day precisions) were less than 5.66%. The proposed method was successful in analyzing BA and SA in ketchup and powder bags of instant noodles.