Coleman M R, Mowrey D H
Lilly Research Laboratories, Agricultural Analytical Chemistry, Greenfield, IN 46140-0708.
J Assoc Off Anal Chem. 1990 Nov-Dec;73(6):927-31.
A turbidimetric method is described for determination of tylosin in animal feeds containing urea. This method includes several modified or new steps to existing turbidimetric and AOAC plate assays that improve the extraction of tylosin, remove interferences from feeds, free tylosin activity, concentrate tylosin from low-level feeds, and reduce variability of assay results. A larger analytical sample size has been incorporated into the assay to decrease variability of assay results. A methanol-phosphate buffer extraction solution has replaced the hot buffer and methanol extraction solution. A hydrolysis step, which is not contained in the AOAC plate assay, was developed to free tylosin from the tylosin urea adduct that forms over time in feeds containing urea. A disposable C18 column was used to concentrate tylosin from feeds at levels less than 15 ppm. By increasing the analytical sample size from 25 to 100 g, the coefficient of variation for 12 weighings of cattle feed was reduced from 28.4 to 9.3%. Average recoveries from cattle rations containing tylosin at levels of 8, 10, and 100 ppm were 94, 94, and 91%, respectively.
本文描述了一种用于测定含尿素动物饲料中泰乐菌素的比浊法。该方法对现有的比浊法和美国官方分析化学师协会（AOAC）平板法进行了若干改进或新增步骤，以提高泰乐菌素的提取率、消除饲料干扰、释放泰乐菌素活性、从低含量饲料中浓缩泰乐菌素并降低测定结果的变异性。测定中采用了更大的分析样本量以降低测定结果的变异性。用甲醇 - 磷酸盐缓冲液提取溶液取代了热缓冲液和甲醇提取溶液。开发了一个AOAC平板法中未包含的水解步骤，以从含尿素饲料中随时间形成的泰乐菌素 - 尿素加合物中释放泰乐菌素。使用一次性C18柱从含量低于15 ppm的饲料中浓缩泰乐菌素。通过将分析样本量从25 g增加到100 g，牛饲料12次称重的变异系数从28.4%降至9.3%。含8、10和100 ppm泰乐菌素的牛日粮的平均回收率分别为94%、94%和91%。
