1. The radioisotope results were usually lower than the microbiological assays and the recovery of added folic acid was less than ideal. These differences should not have been due to folate binders in the test serum, a cause of low results in some radioisotope tests (Rothenberg and da Costa, 1974), because the serum was heated to inactivate the binders. However, this step was carried out without the protective effect of ascorbic acid, except in the experiment concerning shelf-life (Table 1) when, interestingly, the results
2. Radioassay of serum folate;Dunn, R.T.; Foster, L.B.;Clinical Chemistry,1973
3. pH dependence of the binding of folates to milk binder in radioassay of folates;Givas, K.K.; Gutcho, S.;Clinical Chemistry,1975
4. Serum B12 and folic acid assays-a critical view;Hayward, M.J.; Ford, A.;Health Bulletin,1974
5. Method of assay of red cell folate activity and the value of the assay as a test for folate deficiency;Hoffbrand, A.V.; Newcombe, B.F.A.; Mollin, D.L.,1966