Study On The Method Of Multi-Pesticides Residues In Sulfur-containing Vegetables

The consumption of pesticide is increasing day by day in company with agricultural development. More people pay attention to all kinds of problem which are caused by pesticide residues. The analytical method of pesticide residues include extraction, cleaning up, detection and data processing. The residual pesticides in animal and plant is very low. So we must extract them with solvent from the sample at first, clean up to eliminate interfering substance, then detect by instrument, at last, count the pesticide residual date in sample.There are a lot of sulfur compounds in Allium plants. These compounds are difficult to eliminate and brought severe interferences when we detect the pesticide residue. The paper base on the character of sulfur compounds in Allium plants. We could destroy activity of alliinase by phosphoric acid, in order to eliminate interferences of sulfur compound. The pesticide residues in Allium plants were extracted with acetonitrile and by homogenate, cleaned by gel permeation chromatography, then the pesticide residues were detected by gas chromatography and gas chromatography-mass spectrometry. The detailed content and result in research are as follows:1. Because phosphoric acid could destroy activity of alliinase, the condition of phosphoric acid had been studied. The different concentration and volume levels of phosphoric acid were put in 100g samples and the vegetables were cut up by different ways. Then the samples were extracted with acetonitrile and by homogenate, cleaned by gel permeation chromatography, detected by Gas chromatography-electron capture detector. The results of this research indicated that adding 50mL 30% phosphoric acid in 100g samples was better and how to cut up samples had no effect. The stability of organophosphorus pesticides, organochlorine pesticide and pyrethroid pesticides had been studied. A little of pesticides had been lost, so pretreatment with phosphoric acid could be applied to analyze pesticide residues in Allium plants. 2. Extraction method, extraction solvent, evaporated method and collection time of gel permeation chromatography had been optimized. The methods of gas chromatography-electron capture detector and gas chromatography-flame photometric detector detection had been developed. According to the result, acetonitrile and homogenate was selected, solvent was evaporated on electric hot plate, gel permeation chromatography collection time was 8-14min. The recoveries of 10 pyrethroid pesticides,14 organochlorine pesticides and 16 organophosphorus pesticides in Allium plants were obtained. The pyrethroid pesticide and organochlorine pesticide recoveries ranged 72%～125% and limits of detection were between 0.1～4.7μg/kg. The organophosphorus pesticide recoveries ranged 70%-115% and limits of detection were between 0.2～27μg/kg. The method was suitable to analyze multi-pesticide residues in Allium vegetables.3. The selected ion of 43 pesticides had been determined by comparing the pesticide standard samples chromatogram and garlic blank sample chromatogram. The methods of electron impact ionization source-selected ion monitoring mode-gas chromatography-mass spectrometry detection had been developed. The recoveries of 10 pyrethroid pesticides,14 organochlorine pesticides and 19 organophosphorus pesticides in garlic were obtained. All pesticide recoveries ranged 65%～115% and limits of detection were between 0.5～9.0μg/kg. The method was suitable to analyze multi-pesticide residues in Allium vegetables.