Study On Residue Determination Of Avermectin In Aquatic Products And Pharmacokinetics In Grass Carp

Avermectins are a class of drugs which have been found wide usage against a board spectrum of nematodes and arthropods, many of which are important endoparasites and ectoparasites of animals. Avermectin is a common agricultural pesticide produced by the actinomycete Streptomyces avermitilis and registered for worldwide use. It is effective in controlling different phytophagous pests of field crop, ornamentals, vegetables, fruits and in controlling fire ants. This study developed a method to detect avermectin residue in aquatic products using high performance liquid chromatography with fluorescence (HPLC-FLD) detector. Pharmacokinetics and elimination rules of avermectin in grass carp were investigated in this paper.In this paper, the method for the determination of avermectin residue in aquatic products was developed using solid phase extraction and high performance liquid chromatography with fluorescence detector. The sample was extracted with acetonitrile and dehydrate by anhydrous sodium sulphate, and then claned up using solid phase extraction on alumina-B, followed by derivatization with N-methylimidazole(NMIM) and trifluoroacetic anhydride(TFAA) in acetonitrile, and analyzed by HPLC with fluorescence detector set at 365 nm excitation and 475 nm emission wavelengths. The calibration curve of avermectin at the concentration range of 1.0～100.0μg/L was linear (r = 0.9998). Average recovery of avermectin ranged from 80.28 %～98.46 %, the coefficient of variation was 2.86%～9.68% , and the limit of detection was 0.1μg/kg.Then, the accumulation and elimination rules of AVM in the tissues, such as muscule, liver, kidney, plasma and gill of grass carp, have been studied. Tissues samples were collecter at every different intervals after following single bath administration at a dose of 0.3μg/L when the water temperature at 26±1℃. Samples were determined by HPLC-FLD after being homogenized and extracted. Three concentration levels ( 5.0μg/kg,20.0μg/kg,100.0μg/kg ) of avermectin were analysed,the recoveries of all samples were between 78.59 % and 94.75 % ,the inter-day coefficient of variance was between 2.24% and 7.81%, the intra-day coefficient of variance was between 3.57% and 8.37%. The main pharmacokinetics parameters of avermectin in grass carp plasma indicated that avermectin was distributed widely and eliminate slowly. The concentration of avermectin in liver was more higher than any other tissues, and then in kidney, plasma, muscle and gill. The concentrations of avermectin reached the highest value both in grass carp muscle, liver, kidney and gill 72h after administration, and which was the highest valued 17.8μg/kg in the liver, followed by kidney(12.1μg/kg), muscle(10.7μg/kg) and gill(5.2μg/kg).however the highest concentration of avermectin reached at 48h after administration valued 11.2μg/L; It cannot be detected 528h after administration in the tissues of grass carp. The concentrations of avermectin in water eliminated with the influence of some factors, such as metabolism, light, and it cannot be detected 14d after administration.Finally, a pharmacokinetics and residues study of avermectin (AVM) was investigate after following single oral gavage administration in grass carp at 26±1°C water temperature.The concentrations of avermectin in grass carp plasma,liver and muscle were determined by using the High Performance Liquid chromatography with fluorescence detector. Pharmacokinetic parameters were analyzed with the pharmacokinetic computer program 3P97.The results indicated that when grass carp were taken single-dose avermectin 0.1mg/kg by oral administration. The plasma concentration time data of avermectin could be described by a two-compartment open model. The main pharmacokinetic parameters were as follows: The absorption rate constant (ka) of avermectin was to be 0.056; whereas the elimination half-life(T1/2β) of the drug was 218.71h; The area under the serum concentration-time curve (AUC) was 1638.03μg·h/L,and the distribution volume (V_d/f) of avermectin was computed as 0.0026μg/L ,the time-point of maximum plasma concentration of the drug (T_max) and the maximum plasma concentration (C_max) were calculated as 24.00h and 18.51μg/L. At fourteen days after dosing, the concentration of avermectin in edible tissues muscle and liver were lower than MRLs of the same kind medicines, it was suggested WDT was 14d after following single oral administration at a dose of 0.1mg/kg.