GC Determination of 4 Organophosphorus Pesticides in Chinese Herbal Medicines with Separation and Purification by Matrix Solid-phase Dispersion and Soxhlet′s Extraction in Combination

An extractor combining the matrix solid-phase dispersion (MSD) and Soxhlet′s extraction (SXE) was designed. Powdered medicine sample was pulverized and dispersed with fluorisil to give a homogeneous mixture,which was added to the extraction column together with some anhydrous sodium sulfate. Definite amounts of anhydrous Na2SO4,fluorisil and graphitized carbon black were previously added to the column before the addition of the sample mixture. A mixed solvent of acetone and ethylacetate (1+4) was used as extractant,and the extraction performed under heating for 20 min. Separation and purification of the 4 organophosphorus pesticides were fulfilled in this process. The extract was evaporated to near dryness in a water bath at 40 ℃. One mL of acetone was added to taken up the residue and the solution was used for GC analysis. Flame photometric detection was used in the determination. Detection limits (3S/N) found were ranged from 0.006-0.008 mg·kg-1 for the 4 pesticides. Values of recovery found for the 4 pesticides were in the range from 75.1%-97.8% and values of RSD′s (n=5) were in the range of 2.9% to 13.9%.