Studies On Multiresidue Analytical Method And Dissipation Of Pyrethroid Pesticides In Edible Fungi

The multiresidue analytical method of bifenthrin, fenpropathrin, lambda-cyhalothrin, beta-cypermethrin, fenvalerate and deltamethrin was established in Flammulina velutipe, Pleurotus ostreatus and substrate. The residual dissipation dynamics in Pleurotus ostreatus and substrate and transfer of pyrethroids from substrate to Pleurotus ostreatus were studied. Influence of substrate sterilization on pyrethroid residues was analyzed. Removal of pyrethroid residues in Pleurotus ostreatus by different washing patterns was studied in this dissertation. The main results were summarized as following:1．The multiresidue analytical method for pyrethroids residues in Flammulina velutipe, Pleurotus ostreatus and substrateResidues of selected pyrethroid pesticides in Flammulina velutipe, Pleurotus ostreatus and substrate were detected by gas chromatography with electron capture detection. The samples were extracted by acetonitrile, cleaned up by Florisil column. The minimum detectable concentrations of bifenthrin, fenpropathrin and lambda-cyhalothrin were0.005mg kg-1, and the minimum detectable concentrations of beta-cypermethrin, fenvalerate and deltamethrin were0.01mg kg-1. The different concentrations of0.005-1mg kg-1were fortified respectively, and the average recoveries of pyrethroids in Flammulina velutipe were85.54-102.27%, the related standard deviations(RSDs) were1.24-9.58%. The recoveries and RSDs in Pleurotus ostreatus were83.80%-113.98%and1.32%-13.26%. The average recoveries and RSDs in substrate were91.46%-105.83%and1.60%-8.26%. The results showed that the method accorded with demands of pesticide residue analysis.2．Dynamics of pyrethroid residues in Pleurotus ostreatusDynamics of pyrethroid residues in Pleurotus ostreatus with water spray or not were studied. The results showed that the dissipation of pyrethroids was correspond to the mathematic pattern in Pleurotus ostreatus. The half-lives of bifenthrin, fenpropathrin, lambda-cyhalothrin, beta-cypermethrin and deltamethrin with water spray were5.06d,3.01d,4.10d,3.63d and4.06d, respectively. The half-lives of bifenthrin, fenpropathrin, lambda-cyhalothrin, beta-cypermethrin and deltamethrin without water spray were7.09d,4.01d,5.08d,4.72d and4.86d, respectively. The dissipation rates of pyrethroids with water spray were quicker. 3．Influences of substrate sterilization on pyrethroids residuesSterilization has greatly influence on the residues of selected pyrethroid pesticides in substrate. We found that the degradation rates of bifenthrin and fenpropathrin were approximately20%and the degradation rates of lambda-cyhalothrin,beta-cypermethrin and deltamethrin were above50%. The degradation of selected pyrethroid pesticides by sterilization was considered mainly due to the high temperature.4．Dynamics of pyrethroid residues in substrateThe results showed that the dissipation of selected pyrethroids in substrate was correspond to the mathematic pattern. The dissipation half-lives of bifenthrin, fenpropathrin, lambda-cyhalothrin, beta-cypermethrin and deltamethrin were54.59d,21.07d,36.01d,25.48d and39.38d, respectively. Compared with the dissipation rates of pyrethroids in Pleurotus ostreatus, the rates of pyrethroid residues in substrate were slower, and the half-lifes were greater than21d.5．Transfer of pyrethroid residues from substrate to Pleurotus ostreatusThe results showed that residues of bifenthrin, fenpropathrin, lambda-cyhalothrin, beta-cypermethrin and deltamethrin were0.32-1.78mg kg-1after84d in substrate.But residues of pyrethroid pesticides had not been detected in the quartic Pleurotus ostreatus. The above results indicated that the pyrethroid pesticides could not been absorbed by Pleurotus ostreatus and did not transfer from substrate to Pleurotus ostreatus. So, the pyrethroid residues in substrate have no influence on the quanlity of Pleurotus ostreatus.6．Removal of pyrethroid residues in Pleurotus ostreatus by different washing patternsRemoval of selected pyrethroid residues in Pleurotus ostreatus by two different washing patterns was studied. The results showed that two kinds of washing patterns both had good effects on the residues removing of selected pyrethroid pesticides in the Pleurotus ostreatus. We found that about37.75-89.09%of pyrethroid pesticides could be removed by washing with water, and about22.52-55.69%of pyrethroid pesticides residues could be removed by soaking with water. The results indicated that washing with water had the better effect on the removal of selected pyrethroid residues in Pleurotus ostreatus than soaking with water.