Document rx7r65Z6Na1NBboGgK0G0kBE

bee: 0. Roush . J. P, ULeiire "^wr'*W. Withers R. G, Potter W. C. Hnmmann MAR 1 1976 March 1, 1976 Dr, James R. Allen, D.V.M, Dept, of Pathology University of Yilsconsln Madison, Wisconsin 5^306 Dear Dr. Allen: In response to your request for the analysis of chlorodlbenzofurans In polychlorinated biphenyls this analysis 13 the method originally developed b y Vos et al (Food Cosmat, Toxicol, 8, 625 (1970)). We have attempted to use this and other methods to measure chlorodlbenzofurans In PCB's. Our experi ments have Included repeated analyses of PCB's to which known amounts of chlorodlbenzofurans have been added, Wo have achieved incomplete and vari able recoveries because of Incomplete separation of the dibensofuran3 from the PCB's, especially for dl-, trl-, and totrachlorodibenzofursns. Bowes et al (Nature 52, 305 (1975)) also observed incomplete separation of lower chlorodlbenzofurans from*PCB's. Until a more accurate and reproducible procedure is available, v;e are unable *to obtain reliable Infor mation on the chlorodlbenzofuran content of PC3 mixtures. Therefore, wo are returning the samples obtained from you without testing the same since It la our opinion, any results would be Inconclusive, , Sincerely, J, C o l eman Vieber | Manager, Product Acceptability Specialty Chemicals Division bb NEV 036316