Development of a Multiresidue QuEChERS-DLLME-Fast GC-MS Method for Determination of Selected Pesticides in Yogurt Samples

In this study, a combination of modified quick easy cheap effective rugged and safe extraction (QuEChERS) and dispersive liquid-liquid microextraction (DLLME) has been proposed for the extraction and preconcentration of multiclass pesticide residues from yogurt samples prior to their determination by fast gas chromatography-mass spectrometry. Factors influencing DLLME efficiency, including type and volume of extractive solvent, mixing type, salt addition, and extraction time were evaluated. The obtained extract from the first step of QuEChERS was subsequently adjusted by DLLME using tetrachloroethane as an extractive solvent. The method was fully validated within the optimized extraction parameters. The recoveries of pesticides were between 70 and 120% with relative standard deviations less than 20%. The limits of detection ranged between 0.04 ng/L and 2.00 mu g/L, and the limits of quantification ranged from 0.12 ng/L to 6.60 mu g/L. The optimized method was employed for the determination of pesticides in real samples of yogurts.