Liquid chromatographic method for determination of arprinocid in feed: collaborative study

An HPLC method for determining arprinocid [9-(2-chloro-6-fluorophenyl)methyl-9H-purin-6-amine] in feed was evaluated in an interlaboratory collaborative study. The samples were prepared in pairs from feeds obtained from 2 commercial feed manufacturers to cover the concentration range 0.0050-0.0070% arprinocid and were distributed to 14 laboratories. Each collaborator was requested to perform one determination on each of 6 samples. In this analytical procedure, the drug is extracted into CHCl3 and, after appropriate sample preparation by liquid-liquid partitioning, determined using a silica column and ultraviolet detection. The means of the analyses reported by the collaborators ranged from 97 to 104% of the true concentration of arprinocid and were not significantly different (P greater than 0.1) from the true values. The average coefficient of variation was 6.8%. The precision standard deviations of the 3 unit blocks (sr) were each less than 0.0004% arprinocid, and the F-test demonstrated that systematic error (sb) did not make a statistically significant contribution (P greater than 0.1) to the standard deviation of the data (sd). This method has been adopted official first action.