Stir bar sorptive extraction combined with deep eutectic solvent-based dispersive liquid–liquid microextraction: application in simultaneous derivatisation and extraction of acidic pesticides

In the present study, a stir bar sorptive extraction (SBSE) method coupled with deep eutectic solvent (DES)-based dispersive liquid–liquid microextraction (DLLME) has been developed for the simultaneous derivatisation and extraction of some acidic pesticides before their analysis by gas chromatography-mass spectrometry (GC-MS). In this method, initially, the analytes are adsorbed on a coated stir bar from an aqueous solution. Then, the stir bar is removed and a water-miscible DES is used to elute the analytes. Afterwards, butyl chloroformate (BCF) and a water-immiscible DES are added to the obtained elute as a derivatisation agent and an extraction solvent, respectively. In this work, the use of common toxic organic solvents is omitted, and for the first time, DESs are used as elution (for desorption of the analytes from stir bar), disperser and extraction solvents. Under the optimum conditions, the introduced method indicated high enhancement factor (EnF) (1743–3654), enrichment factor (EF) (1232–1532), and extraction recovery (ER) (74–92%), low limit of detection (LOD) (14–29 ng L^–1) and limit of quantification (LOQ) (47–98 ng L^–1), good linearity (r² ≥ 0.9969) and satisfactory repeatabilities. Finally, the proposed method was applied in the analysis of the analytes in various fruit juice samples.