Determination of the residual tetracycline antibiotics in the manures of livestock via the solid-phase extraction-high performance liquid chromatography method

This paper is to introduce the solid-phase extraction-high performance liquid chromatographic method(SPE-HPLC) developed by us for simultaneous determination of the three typical tetracycline antibiotics including oxytetracycline(OTC),tetracycline(TTC) and chlortetracycline(CTC) residues in the livestock and poultry excrements.It intends to build up and optimize the extraction process as well as the chromatographic analysis condition so as to detect the target antibiotics accurately and promptly.To achieve this purpose,we have extracted the tetracycline antibiotics from the excrement samples through Na2EDTA-Mcllvaine buffer solution(pH=4.0),and then cleansed them up by HLB solid phase extraction column to remove the impurities.And,next,we have analyzed the samples by high-performance liquid chromatographic detector with ultraviolet detection.As the result of the analysis with the optimized method,we have discovered that the chromatographic column is Zorbax Eclipse plus-C18(250 mm×4.6 mm,5 μm),whereas the mobile phase is 0.01 mol/L sodium dihydrogen phosphate solution/acetonitrile(V/V=78/22,pH=2.5),with the wavelength being 355 nm,the column temperature being 25 ℃,with the flow velocity(1.0 mL/min,and the incoming sample quantity(10 μL.The method detection limits(MDL) of the three tetracycline antibiotics prove to be 0.035 mg/kg,0.037 mg/kg and 0.052 mg/kg,respectively.While the recovery rates at different spiked level(10 μg/kg,20 μg/kg and 50 μg/kg) turn to be between 89.7% and 96.8%,with relative standard deviations(RSD) being from 1.6% to 2.3%(n=5),the detection method tends to be linear primarily with the correlation coefficients running into 0.999 9 for tetracycline antibiotics except for tetracycline(R2=0.9997).Thus,it can be seen that the analysis method established in this paper can be widely used for determining the residual tetracycline antibiotics in the excrements of other domestic animals and poultry for its easy operation,time-saving,high accuracy and cost-effective.In this paper,the three tetracycline antibiotics were selected in all the six large-scale piggery farms in suburban areas of Beijing,in a concentration range from 1.37 mg/kg to 25.15 mg/kg.