Microbiological determination of neomycin in feeds: collaborative study
Stahl, G.L.; Kratzer, D.D.; Kasson, C.W.
Journal - Association of Official Analytical Chemists 72(2): 237-241
1989
ISSN/ISBN: 0004-5756 PMID: 2651392 Document Number: 330980
A modification of the AOAC microbiological determination of neomycin in feeds was collaboratively studied by 12 laboratories. The official method was modified by substituting a constant salt concentration diluent for the feed extract diluent, preparing the agar medium in tris buffer, and performing the test with a monolayer plating system. Each laboratory performed single assays on 8 samples in a randomized sequence. The samples included duplicates of a cattle and swine feed at 2 different marketed concentrations. The mean recovery across all laboratories was 110.7% of theory with a range of means of 69.4-128.6 across the 12 laboratories. The results of one laboratory and 2 additional values from different laboratories were deemed outliers and excluded from statistical analysis. The statistical analysis gave a confidence interval of +/- 26% for individual assays.