(ii) The chick-edema factor bioassay method described under "26. Oils, Fats, and Waxes" in the Journal of the Association of Official Agricultural Chemists, Vol. 44, Page 146 (1961), or the method described under "Chick-Edema Factor-Bioassay Method (34)-Official Final Action" in §§ 28.113-28 .117, "Official Methods of Analysis of the Association of Official Analytical Chemists," 12th Ed., 1975, pp. 509-511, which is incorporated by reference, shall be employed. (Copies of the methods are available from the AOAC INTERNATIONAL, 481 North Frederick Ave., suite 500, Gaithersburg, MD 20877, or available for inspectionat the National Archives and Records Administration (NARA). For information on the availability of this material at NARA, call 202-741-6030, or go to: http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html. ) The presence of chick-edema factor shall be determined by a comparison between the mean log of the pericardial fluid volumes of a test group and of a concurrent negative control group. The significance of the difference in pericardial fluid volumes between the test group and the negative control group is determined by calculating a "t" value according to the formula: View Image
where:
xt and xc are the means of the logs of the pericardial fluid volumes of the test and control groups, respectively;
nt and nc are the number of chicks in the respective groups;
st2 and sc2 are the variances of the test and control groups, respectively.
The variances are calculated as follows:
View Image
where:
[SIGMA]x is the sum of the logs of the pericardial fluid volumes;
[SIGMA]x2 is the sum of the squares of the logs of the pericardial fluid volumes for either the test t or control c group data.
The test sample is judged to contain chick-edema factor if the calculated "t" exceeds +1.3 and the mean log of the pericardial fluid volume obtained from the negative control group multiplied by 100 is less than 1.1461.