A chemical routine determination of vitamin‐D; correlation with the biological determination. (Analysis of fat soluble vitamins II))

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Abstract
A chemical routine method for the determination of vitamins‐D2 and ‐D3 in a number of preparations is presented. The results obtained agree very well with those obtained with the rat and chick assays respectively.A procedure for the routine determination of vitamin‐D especially for synthetic ergo‐ and chole‐calciferol is described in detail.It is a combination of a maleic anhydride addition extrapolated to zero time, and a colorimetric determination with antimony trichloride. Solutions of crystalline calciferols, irradiation products (resins and solutions in oil or volatile solvents), emulsions, solubilized solutions and dry products are covered by this method.The concentration limit after removal of volatile solvents from the products or from an extract is about 50,000 I.U./g.Interferences by fatty oils, unsaturated acids, by‐products from the irradiation, especially tachysterols, are allowed for. Interference by vitamin‐A could not be eliminated however.A determination takes about 200,000 I.U. A number of representative analyses is presented.The coefficient of variation is about 2 %.The curative test (rat assay) for vitamin‐D2 and the prophylactic test (chick assay) for vitamin‐D3 give essentially the same results (94.4 ± 16.7 % and 106.8 ± 15.8 %) as the chemical determination.It is possible to substitute the determination presented here for the bio‐assay as an analytical routine method.