Sample preparation by dispersive liquid-liquid microextraction for determination of pesticide residues in ginger

Abstract

In this thesis, the multiresidues of organophosphates (OPPs), organo- chlorines (OCLs) and pyrethoids (PYs) pesticides in ginger were determined. The OPPs, OCLs and PYs pesticides in ginger sample were extracted by liquid-liquid extraction with acetonitrile combined with dispersive liquid-liquid microextraction (DLLME) and analyzed by gas chromatography–mass spectrometry. Various parameters that affected the extraction efficiency of DLLME including type and volume of extraction and disperser solvents, extraction time, centrifugation time, salt addition, and pH were evaluated. The optimum conditions were using 50 μL of tetrachloroethylene as the extraction solvent, 1 mL of acetonitrile as the disperser solvent, extraction time of 2 min, centrifugation time of 5 min, and the addition of 4% of sodium chloride. Recovery tests were performed at concentrations levels of 5.0, 15.0 and 100.0 ng/g; recoveries for each target were in the range between 60 to 105%. Limits of detection and limits of quantitation of this method were ranging from 2.2 to 3.1 ng/g and 7.2 to 10.2 ng/g, respectively. The repeatability of the proposed method, expressed as HORRAT, was in range from 0.13 to 1.86. Compared with the conventional sample preparation method, the proposed method has the advantage of being quick and easy of operation, and low consumption of organic solvent.