Development of ultrasound-assisted dispersive liquid-liquid microextraction-large volume injection-gas chromatography-tandem mass spectrometry method for determination of pyrethroid metabolites in brain of cypermethrin-treated rats

3-Phenoxybenzoic acid (3-PBA) and 4-hydroxy-3-phenoxybenzoic acid (OH-PBA) are the two common metabolites for most pyrethroid insecticides. A rapid, sensitive, and eco-friendly method has been developed based on ultrasound-assisted dispersive liquid-liquid microextraction (DLLME) coupled to large volume injection-gas chromatography-tandem mass spectrometry for the simultaneous determination of pyrethroid metabolites in rat brain treated with cypermethrin (CYP). Brain samples were homogenized in methanol (disperser solvent) followed by derivatization with methyl chloroformate (MCF) and extraction using DLLME. Factors that influence the extraction and derivatization efficiency such as type and volume of extraction and disperser solvent, sonication time, pH, ionic strength, and volumes of MCF and pyridine were optimized. Under optimized conditions, the limits of detection were 1 and 4 ng/g for 3-PBA and OH-PBA, respectively. Mean recoveries of pyrethroid metabolites in rat brain were in the range of 83-95 %. The developed method was successfully applied for determination of 3-PBA and OH-PBA in brain samples of CYP-treated rats. The developed method can be adopted for rapid and sensitive analysis of pyrethroid metabolites in toxicological and forensic laboratories.