Study On Residues And Elimination Of Nitrofuran Metabolites In Carassius Auratus Under Combination Medication

Our country is the world’s largest aquaculture country and the only country in the world whose aquaculture production exceeds the catch.However,in recent years,in order to improve economic efficiency,some farmers have illegally used banned fishery drugs and chemical antibiotics,and even used multiple drugs in combination to treat complex fish diseases,which not only caused serious drug residues in aquatic products,but also caused ecological environmental pollution,and form a vicious circle.Nitrofuran drugs are a kind of broad-spectrum antibiotics that have been widely used to treat a variety of bacterial fish diseases.Their metabolites can remain in aquatic animals for a long time and have potential triple effects,they have been listed as banned in many countries.At present,the illegal use of nitrofuran drugs in aquaculture still occurs from time to time.Therefore,the detection and supervision of nitrofuran drugs cannot be relaxed,at the same time,due to the combined use of drugs by farmers and the complexity of the ecological environment.The rule of residue and elimination of nitrofuran drugs in aquatic animals is necessary under medication.This subject takes Carassius auratus as the research object,established a detection method suitable for four nitrofuran metabolites residues in Carassius auratus,and explored the residual and elimination rules of nitrofuran metabolites in Carassius auratus under single and combined administration,analyze the residue and elimination of furazolidone metabolites in Carassius auratus by different fishery drugs,the main research contents are as follows:（1）A residual detection method for four nitrofuran metabolites in Carassius auratus has been established.Methods constant temperature ultrasound assisted derivatization was used to select the optimal extraction p H,the visceral samples were degreasing and purged using PSA and n-hexane in two steps,determined by high performance liquid chromatography-tandem mass spectrometry,and quantified by internal standard method.The results show that under this method,the four nitrofuran metabolites have a good linear relationship within the concentration range of 1.0-100.0 ng/m L,the correlation coefficients are all greater than 0.999,and the detection limits and quantification limits are 0.25μg/kg and 0.5μg/kg.At the spiked levels of 1.0μg/kg,5.0μg/kg,and 10.0μg/kg,the average recoveries of the four nitrofuran metabolites in Carassius auratus muscle,liver,and kidney are between 91.34%and 107.31%,and the relative standard deviation of this method is 1.44%～7.89%.The experimental results show that the method has high sensitivity and good reproducibility,and can provide technical support for the detection of nitrofuran metabolite residues in Carassius auratus.（2）Carassius auratus was used as the experimental object,and raised by medicated bath administration,and Carassius auratus muscle was taken at different time points after the medicated bath,the residual amount of nitrofuran metabolites in the Carassius auratus muscle was analyzed by HPLC-MS/MS.The results found that:within the same elimination time,when the four nitrofuran drugs were administered alone or in combination,their metabolites showed different residual and elimination rules in the Carassius auratus body,and the residual and elimination changes of AOZ were the most obvious,the maximum residual amount and average elimination rate of AOZ in Carassius auratus muscle during combined administration were 23.37μg/kg and 0.14μg·（kg·h）^-1,respectively,while the maximum residual amount and average elimination rate of AOZ were only 12.40μg/kg,0.09μg·（kg·h）^-1.Since AOZ showed great differences in the rule of residue elimination under two different administration modes,single and combined administration,therefore FZD was combined with NFZ,FTD,and NFT to analyze the effects of the three drugs on AOZ residues in Carassius auratus,The results showed that FTD had the greatest effect on the residual amount of AOZ in Carassius auratus during the combined administration,the maximum residual amount of AOZ in the combined FZD and FTD group was 30.52μg/kg,which was 2.03 times that of the control group.（3）Based on the previous chapter,it was found that AOZ has obvious changes in the elimination of residues of the four nitrofuran drugs alone and in combination,considering that there may be multiple fishery drug residues in the actual breeding environment,the drug bath is used for administration,after the drug bath is over,Carassius auratus muscles,kidneys and liver were taken at different time points to analyze the residual amount of AOZ in Carassius auratus,and further explore the residue and elimination of FZD metabolite AOZ in Carassius auratus with the participation of different fishery drugs.The results showed that after six fishery drugs（chloramphenicol,oxytetracycline,enrofloxacin,sulfamethazine,methyltesto-sterone,and diethylstilbestrol）were combined with FZD,the residue and elimination of AOZ in Carassius auratus muscle,kidney and liver will be affected to varying degrees.Among them,oxytetracycline and enrofloxacin have a greater impact on the residue and elimination of AOZ in crucian carp,FZD combined with oxytetracycline,enrofloxacin,the maximum residual concentration of AOZ in Carassius auratus muscle,kidney,and liver were 28.69μg/kg,152.46μg/kg,125.19μg/kg;6.98μg/kg,40.70μg/kg and 41.64μg/kg,it is approximately 2.13,1.86,2.11 times,0.65,0.84,0.46 times of the control group;the average elimination rates were 0.33μg·（kg·h）^-1,1.71μg·（kg·h）^-1,1.23μg·（kg·h）^-1;0.08μg·（kg·h）^-1,0.30μg·（kg·h）^-1,0.44μg·（kg·h）^-1,approximately 2.36,1.20,2.37 times;0.57,0.35,0.85 times of the control group.