Research Of Determinative Methods Of Drug Residues In Milk

The use of drugs is prevalent in animal breeding,kinds of antibiotic and sulfonamides are widely used to prevent and treat diseases such as bovine mastitis. With the public increasingly concerned about food safety,drug residues in milk are also more and more attention.The misuse of drug in animal breeding could cause residues in milk.these residues may influence human food security and pollute environment possibly.Therefore,it is necessary to establish the determinative methods of drug residues in milk.The main research area in this thesis can be included as follows:1 Assay on residue of antibiotics in pure milk from market by TTC methodObjective:Inquiring into pure milk situation of antibiotic residues from Chengdu market.We added experiments of bacilli dilution test to TTC,to find a better dilution ratio which meets the needs of the indicator.Methods:Detecting pure milk situation of antibiotic residues in the Chengdu market by TTC;we added experiments of bacilli dilution test to TTC.Results:In order to understanding the situation of antibiotics residue in pure milk in Chengdu market,we selected 60 samples by random and detected residue of antibiotics by TTC.Among these samples,two were found out positive and one was suspect.The positive ratio is 3.3%and suspect ratio is 1.7%.The experiments showed that by diluting the bacilli solution with sterilized skim milk in the proportion of 1:10,we can get a more accurate detecting result of antibiotics residue.Conclusion:The sampling test results are satisfactory.The ratio of 1:10 dilution of bacterium is better than 1:1 dilution which is stipulated in national standards.It is more accurate than national standard.2 Practicality of detection on sulfonamide residues in milk by TTC methodObjective:This study tries to employ TTC method to examine the sulfonamide residues in milk,and try to evaluate practicality of this method.Methods:The method of GB/T 4789.27-2003 was employed to evaluate the practicability of the microbiological method that was used to analysis of sulfonamides residues in milk. Results:Using TTC method to detect sulfonamides residues in milk is obvious limitations.Conclusion:This method was simple,easy to operate and not requiring expensive apparatus or equipments.While time-consuming,unquantitative were its shortage;the most important was that the sensitivity of this method was very low, the detection limit was higher than maximum residue limitation of sulfonamide residues in milk and the method was poor in practicability.3 Milti-residues determination of three sulfonamides in milk by HPLC methodObjective:To establish a method for the determination of sulfadiazine, sulfamethyldiazine and sulfadimidine in milk by HPLC method.Methods:Milk containing sulfonamides was extracted with chloroform acetone mixture(2:1,V/V) twice.The extract was combined and evaporated to dry,then dissolved in methanol-0.04%phosphate(30:70,V/V).The chromatographic conditions were as follows:Hypersil ODS2(250mm×4.6mm,5μm elite,Dalian).Mobile phase of methanol-0.04%phosphate(30:70,V/V),low rate being 0.8mL/min,detection wavelength at 272nm and the column temperature at 30℃,injection volume 10μL.Results:A good linear relationship exists for all residues in concentration range of 0.02～1.0mg/L,while the detection limit for sulfadiazine,sulfamthyldiazine and sulfadimidine were 0.050mg/L.The average recovery of sulfadiazine, sulfamthyldiazine and sulfadimidine were 91.5～97.4%,90.5%～98.6%, 76.7%～89.0%.Conclusion:This method is simple,accurate,reliable and of good reproducibility.It can be used for the detection of sulfadiazine,sulfamthyldiazine and sulfadimidine.