Studies On Screening Determination Of Multiclassification Multipesticide Residues In Vegetables

As the improvement of living standards,food safety has greatly attracted by people, especially the pesticide residues in fruit and vegetable. As the same time, governments and organizations have adopted increasing -ly stringent limits,with the maximum residue limits of pesticides from the original mg/kg reduced toμg/kg, with even some pesticides been classified asprospective detection and the number of limited pesticides growing,so china's exported vegetables faces more and more severe technical barriers to trade. In recent years, the international developing on detection method of pesticide residues in fruits and vegetables was from a class of some pesticide residues to multiclassification multipesticide residues. The screeni -ng method of multiclassification multipesticide residues was favored by governments and organizations as saving time, effort and hard to undetec -ted. This dissertation focused on the studies of analysis on 106 kinds of organic phosphorus, 60 kinds of amides, 45 kinds of triazole, 34 kinds of N-methyl carbamates, 26 kinds of pyrethroids, 22 kinds of organochlorine and 157 kinds of other species of pesticide residues. After optimizing the sample preparation and instrumental analysis conditions, the screening methods of multiclassification multipesticide residues in vegetable by gas chromatography triple quadrupole tandem mass spectrometry (GC- MS/MS) and ultra-performance liquid chromatography and tandem ion trap-time of flight mass spectrometry (LCMS IT/TOF ) have been stablished.The rapid screening by GC-MS/MS of multiclassification multipestic -ide residues in vegetables was studied. After optimizing the sample preparation conditions as extraction solvent, purification methods and the best mass fragment ions conditions, a multiresidues analytical method was developed for the determination of 262 pesticides in vegetable by GC-MS/ MS. The pesticide residues were extracted from samples by acetonitrile. The extract was cleaned up on a solid phase extraction column which complex carbon with N-propyl ethylenediamine(Carbon GCB/PSA SPE), eluted with the acetonitrile- toluene (3:1, by volumn),evaporated with a stream of nitrogen to near dryness and constant volume with acetone. The detection of pesticides was carried out under electronic ionization source and multiple reaction monitoring (MRM) model. The linear ranges of pesticides were 5μg/L~250μg/L, the correlation coefficients were better than 0.9902 and the limit of detections ranged from 0.1μg/kg to 4.0μg/kg. The method was validated at two fortification levels in basil leaves , the mean recoveries ranged from 33.04% to 197.91% with relative standard deviations (RSDs) of 4.8% ~ 33.4% at a spiked level of 5μg/kg, the mean recoveries were from 43.80% to 198.78% with RSDs of 2.6%~32.5% at a spiked level of 10μg/kg.The rapid screening of multiclassification multipesticide residues in vegetables by LCMS -IT/TOF was studied. After optimizing the sample preparation conditions as extraction solvent, purification methods and the best mass fragment ions conditions, a multiresidue analytical method was developed for the determination of 188 pesticides in vegetable by LCMS-IT/TOF. The pesticide residues were extracted from samples by acetic acid- acetonitrile (1:99, by volumn). The extract was cleaned up on a solid phase extraction column which complex carbon with N- propyl ethylenediamine (Carbon GCB/PSA SPE), eluted with the acetonitrile - toluene (3:1, by volumn), evaporated with a stream of nitrogen to near drynessand , constant volume with methanol. The separation of pesticides was performed on an Shimadzu Shim-pack XR- ODS II (2.0 mm.D.*75 mm, 2.2μm ) by gradient elution with flow rate of 0.4 mL/ min at 40°C. The detection of pesticides was carried out under positive and negative electrospray ionization model in the same time.The linear ranges for pesticides were 5μg/L~250μg/L except acetamiprid,bitertanol,mevinphos of 10μg/L~250μg/L and the correlation coefficients were better than 0.9903 and the limit of detections ranged from 0.02μg/kg to 5.50μg/kg. The method was validated at two fortification levels in broccoli, the mean recoveries ranged from 20.5% to 118.5% with RSDs of 5.8%~30.1% at a spiked level of 5μg/kg, the mean recoveries were from 26.2% to 129.9 % with RSDs of 2.8%~22.8% at a spiked level of 10μg/kg.The screening methods of multiclassification multipesticide residues by GC-MS /MS and LCMS-IT/TOF were established,with the limit of detections less than 10μg/kg, the correlation coefficient better than 0.9902. The methods were to meet the technical needs of administrative law enforcement as market surveilance, origin inspection and port inspection, protect the health of consumers, improve the hygienic quality of exported vegetables, and lay the scientific basis to break down green technical barriers to trade.