Study On The Accumulation And Elimination Of Avermectin In Perch L. Japonicus

Avermectins,a kind of 16-membered macrocyclic lactones,produced by a soil actinomycete Streptomyces avermitilis,are widely used for miticide and insecticide in agriculture for their effective effort.However,whether used for pesticide or veterinary drug,they all might pollute the water because they will be transferred into aquatic environment.The drugs also have been widely used for pestiside,such as sealice in aquiculture,which enhance the pollution of water.Therefore,the drugs will threat the comsumers' health and the aquatic economy when they are discharged to water or used on aquatic animals which will accumulate in these organisms.It is important to study the detection methods of AVMs in seawater and aquatic animals,such as perch Lateolabrax japonicus,and research the accumulation and elimination rules of AVMs in the tissues of perch.In this paper,the methods for detecting AVM and IVM in the tissues of perch L. japonicus and in the seawater by high-performance liquid chromatography(HPLC) with fluorescence detection have been developed.In this method,the samples of perch are extracted with acetonitrile firstly,degreased by hexane and dehydrate by anhydrous sodium sulphate,and then cleaned up using solid phase extraction on alumina-B,followed by derivatization with trifluoroacetic anhydride and N-methylimidazole;Samples of seawater are extracted with ethyl acetate which is not dissolve in water,then dehydrated by anhydrous sodium sulphate,vaporized by N₂, and followed by derivatization with trifluoroacetic anhydride and N-methylimidazole. Then,the extracts are analyzed by the HPLC systems with an Eclipse XDB-C18 RP-column and a fluorescence detector withλ_Ex 365nm andλ_Em 475nm,respectively. The results show that the detection limit of AVM in muscle and gill both are 0.5μg/kg, and that of IVM are 1μg/kg;while that of AVM in blood and liver are 1μg/kg, compared with that of IVM are 2μg/kg.The average recoveries of AVM and IVM in the tissues of perch are 80.1%～90.0%and 73.9%～85.5%,respectively.And the detection limit of these two chemicals in seawater are 0.025μg/L～0.05μg/L and the average recoveries are 95.1%～96.5%and 88.7%～93.9%,respectively.Then,the toxicity of AVM on perch has been studied with semi-static method in this paper.It is found that,the perch is sensitive to AVM,and median-lethal concentration in 96h is 5.2324μg/L.The safe-concentration of avermectin is 0.523μg/L and the safe concentration scope of AVM to perch is narrow,so the dosage must be controlled strictly.Therefore,0.5μg/L is used for the final concentration.Finally,the accumulation and elimination rules of AVM in the tissues,such as muscle,liver,blood and gill of perch,have been studied.The experiment is divided into two processes and totally lasts for 60 days.The first one is exposure process, during which the perch are exposed to 0.5μg/L of AVM and lasts for 20 days.Then the perch are transferred into fresh seawater for elimination process for 40 days.The result shows,AVM can accumulate in the muscle,liver,gill and blood of perch,but the enrichment capacity of each tissue is different.The enrichment capacity of AVM is comparatively stronger in the liver,but relatively weaker in muscle.The C_max of liver can reach to 87.36±0.88μg/kg,and AUC_{肝脏}is12977.73±122.49μg·h/L,whereas the C_max of muscle is 7.74±0.08μg/kg and AUC_{肌肉}is only 2105.75±27.76μg·h/L. Half-time elimination of AVM in the muscle,gill,liver and blood of perch are 6.9days, 9.5days,8.2days and 10.7days.Because many factors affect residues of aquatic animals,pharrnacokinetic parameters of the same drug in different aquatic animals are very different.In this conditions,when the temperature is 15℃～18℃,off-period of 40 days is advised.