Comparative Study On Three Detection Methods Of FQs Residues In Milk

In this research,HPLC,microbiological assay and ELISA were established for determination of FQs drugs residues in milk.,aiming to severe residues problem in milk to our country and having no perfect monitoring system,and a comparative study had been done for three determination methods.In order to provide theoretical basis and technical reference to different scale dairy enterprise and quality control department.1.HPLC was established for determination of Enrofloxacin,Ciprofloxacin and Norfloxacin residues in milk.Milk samples was extracted by PBS and passed Millipore filter,finally determined to use HPLC with fluorescence detector.These standard curves were satisfying linearity in the range of 0.005～0.5μg/mL(r=0.9997～0.9998).The detect limit of this test was 0.005μg/mL.The mean recovery at fortified level of 0.05μg/mL,0.1μg/mL and 0.2μg/mL was 71.5%～83.8%,the coefficients variations(C.V) were below than 10%.This test can meet the requirement to determining residues in milk.2.A cylinder plate microbiological assay was developed for determination of Enrofloxacin,Ciprofloxacin and Norfloxacin residues in milk with Bacillus subtilis,Bacillus pumilus and Micrococcus luteus. First,the concentration of bacteria was confirmed by the inhibition zone diameters and the definition at different time,cinfirmed the limit detection of three FQs in PBS and in milk ,than, based on a dose of method theory,standard curves were draw by use of concentration logarithm of three drugs and the inhibition zone diameter,finally, figured it'recovery. The results showed:the best suitable inoclum concentrations were 0.8%,0.1%,0.5% of the Bacillus subtilis,Bacillus pumilus and Micrococcus luteus respectively.The limit detection of three FQs in PBS was 0.025～0.5μg/mL.In milk,the detection limit was 0.03～0.6μg/mL.,and had showed good linear relationships.The coefficients of variation were all above 0.98.The mean recovery was 63.2～81.0%.CV was below 10%.It may meet the requirement to determining residues.3.This test used kits developed by Beacon company in American,it's theory was ci-ELISA.Milk samples were extracted with Methylene dichloride,centrifugal,dried by N2 detected.Finally,measured absorbance at 450nm,sanmple's absorbance and FQs concentration were inverse relation.The study showed:This kind of kits was fully reliable to determinateFQs drugs resedues in milk.The minimum detection limit was 2μg/mL.The recovery was 60～70%,CV were below 10%.4.The analysis on three detection methods'specificity,speed and cost was conducted that HPLC was accurate qualitative and quantitative method.microbiological assay was the most economic,quick and accurate in the way of screen determination of FQs drugs residues.ELISA was quite suit to screen lots of samples.