Simultaneous determination of olaquindox, oxytetracycline and chlorotetracycline in feeds by high performance liquid chromatography with ultraviolet and fluorescence detection adopting online synchronous derivation and separation.

Olaquindox, oxytetracycline and chlorotetracycline were widely used in feed as antibiotics and growth promoter to improve feed conversion efficiency and increase the rate of weight gain for animals. However, the use of these antibiotics in feed was gradually prohibited because of concerns about contamination and resistance in animals. A quantitative and confirmatory method for determining the presence of olaquindox, oxytetracycline and chlorotetracycline in feed by high performance liquid chromatography equipped with ultraviolet detector in series with fluorescence detector (HPLC-UVD-FLD) was developed, optimized, and validated in three different matrices (compound, concentrated and premix feed). The analytes extraction was performed with a mixture of acetonitrile and 0.1 mol/L ethylenediamine tetraacetic acid disodium-Mcllvaine buffer (1:4, v/v) by one step sample preparation procedure. The validated method presented a broad linear range and good linearity with weighted least square method. The decision limit of the analytes ranged from 0.61 to 0.77 mg/kg for olaquindox, 0.90 to 1.2 mg/kg for oxytetracycline and 1.3 to 2.0 mg/kg for chlorotetracycline. The average recovery values found in intermediate precision conditions were ranged from 88.0 to 99.7% for olaquindox with RSD lower than 11.1%, from 84.4 to 99.0% for oxytetracycline with RSD lower than 9.6%, from 83.8 to 97.5% for chlorotetracycline with RSD lower than 10.0%. By Youden test and bottom-up method, the method was proved to be sufficiently robust and had a small uncertainty for different concentration levels. The developed method was successfully utilized for commercial feed samples to monitor complex cross contamination and residue conditions. Online synchronous derivation and separation using ultraviolet detector in series with fluorescence detector can effectively prevent false positive of chlorotetracycline in feed caused by vegetable meal. Since olaquindox, oxytetracycline and chlorotetracycline are widely used in feed, the developed method provide an important and analytical tool for the simultaneous identification and quantification of them in feed to monitor its risk of cross contamination and excessive content.

Analysis of josamycin in three kinds of feed using ultra high performance liquid chromatography with tandem mass spectrometry.

In this study, a new and accurate method based on ultra-high performance liquid chromatography (UHPLC) with electrospray ionisation tandem triple quadrupole mass spectrometry (MS/MS) was developed and validated for the determination of josamycin in three kinds of feeds (compound, concentrated and premix feeds). The optimised sample pretreatment procedure included extracting from the matrix with a mixture of methanol and acetonitrile (1:1, v/v) followed by drying under nitrogen and redissolving in phosphate buffer solution (pH = 8, 0.1 mol/L) followed by purifying using HLB cartridges. Validation of the method was carried out in three different matrices (compound, concentrated and premix feed) by recovery experiments, using samples spiked at concentration levels of 20, 100 and 200 µg/kg. Satisfactory recoveries from 82.4% to 93.0%, with RSDs lower than 17.4% under intermediate precision conditions were obtained in all feed matrices tested. The developed method was applied to commercially samples and josamycin was found frequently in feed containing kitasamycin.