Harpster C P, Katz S E
J Assoc Off Anal Chem. 1980 Sep;63(5):1144-8.
An improved microbiological assay for erythromycin in milk and some milk products was developed. Acidification of the samples to pH 4.5 resulted in precipitation of milk solids which were separated by centrifugation. The pH of the aqueous supernatant solution was readjusted to pH 8.0 to obtain maximum sensitivity. Th sample cleanup and the use of a single, thin, seeded agar layer with Microsoccus lutea as the assay organism permitted the mesurement of 0.05 micrograms/mL milk with recoveries averaging 84.0%, 0.50 micrograms/g nonfat dry milk with recoveries averaging 55.4%, 0.10 micrograms/g cream cheese with recoveries averaging 100.2%, and 0.05 micrograms/mL buttermilk with recoveries averaging 44.0%. The improved procedures showed superior recoveries and improved the ability to detect and measure lower levels when compared with commonly recommended assay procedures for erythromycin residues.
开发了一种改进的用于测定牛奶及某些奶制品中红霉素的微生物检测方法。将样品酸化至pH 4.5会导致乳固体沉淀，通过离心将其分离。将水相上清液的pH值重新调至pH 8.0以获得最大灵敏度。样品净化以及使用单一、薄层的接种琼脂层，并以藤黄微球菌作为检测微生物，能够测定牛奶中0.05微克/毫升，回收率平均为84.0%；脱脂奶粉中0.50微克/克，回收率平均为55.4%；奶油干酪中0.10微克/克，回收率平均为100.2%；酪乳中0.05微克/毫升，回收率平均为44.0%。与常用的推荐红霉素残留检测方法相比，改进后的方法具有更高的回收率，且提高了检测和测定较低含量的能力。
