Jm. Lynch et al., PERFORMANCE EVALUATION OF THE BABCOCK AND ETHER EXTRACTION METHODS - 1989 THROUGH 1992, Journal of AOAC International, 77(4), 1994, pp. 976-981
Results of the collaborative studies of the performance of the Babcock
method (989.04) and the modified Mojonnier ether extraction method (9
89.05) for the determination of the fat content of raw milk were publi
shed in 1988. Method performances were characterized by using the harm
onized International Organization for Standardization-International Un
ion of Pure and Applied Chemistry-Association of Official Analytical C
hemists (ISO/IUPAC/AOAC) guidelines for method validation, and the met
hods were approved official first action. During 1989 through 1992, th
e split-sample collaborative study format was used to monitor the perf
ormance of these methods as a part of an ongoing quality assurance pro
gram for a group of laboratories. Seven blind duplicate samples of raw
milk were sent from a central laboratory once every 2 months to each
participating laboratory (11 to 17 laboratories). Data were analyzed b
y using the same statistical procedures used in the 1988 study. Over t
ime, both the within- and between-laboratory performances of both meth
ods were as good as or, in most cases, better than the results from 19
88. The data demonstrate that the statistical protocol for collaborati
ve studies can be used effectively as the basis for a multilaboratory
quality assurance program and that the method performance achieved in
a collaborative study can be maintained and even improved with time.