Time required to achieve homogeneity of test substances added to dog feed
Sapienza, P.P.; Ikeda, G.J.; Warr, P.I.; Albert, R.H.
Journal - Association of Official Analytical Chemists 74(5): 857-861
1991
ISSN/ISBN: 0004-5756 PMID: 1783593 Document Number: 377610
The homogeneity of test substances in a carrier (animal feed) is a critical factor in conducting long-term feeding studies in laboratory animals. A method for determining the adequate amount of mixing to achieve homogeneity by a mixer of the type described has been determined when 2 distinctly different compounds are added to ground dog feed. Nicotinic acid and butylated hydroxyanisole at a concentration of 1% were separately mixed with the dog feed for 15, 30, 45, 60, and 120 min to determine optimum mixing time. Test portions were taken from 4 different sampling sites at each time period and analyzed in duplicate for the added substance. Four batches were prepared and the results were aggregated. Very little interbatch variability was observed. The variance of the average values from the 4 sampling sites at each time period was calculated and used as a simple, crude, but effective numerical quantity to monitor the approach to homogeneity of the mixture.