In situ formation of deep eutectic solvent for disperser-free microextraction of Fast Green and Erythrosine in food and pharmaceutical samples.

A rapid, environmentally friendly, in situ deep eutectic solvent (DES) based liquid-liquid microextraction method was proposed for the preconcentration and determination of Fast Green (FG) and Erythrosine (ER) in food and pharmaceutical samples. The DES, which was synthesized in situ without the need for disperser liquids or prior preparation, was composed of thymol and tetrabutylammonium bromide (1:2). Key extraction parameters, including pH, DES ratio, extraction time, temperature, ionic strength, and centrifugation time, were adjusted to achieve maximum efficiency. The interaction mechanism between the dyes and DES was investigated using FT-IR and UV-Visible spectroscopy. Under optimal conditions, the method showed good linearity over 30-1200 µg L⁻¹ for FG and 48-2000 µg L⁻¹ for ER, with detection limits of 9.0 and 13.9 µg L⁻¹ for FG and ER, respectively. The method exhibited high precision (RSD < 4%) and satisfactory recoveries (97.5-99.9%) in spiked samples. Greenness assessment and applicability of the method were assessed using AGREEprep and Click Analytical Chemistry Index tools.