[Biological method of quantitating vitamin D in different preparations and diets]

A biological method for quantitative assay of vitamin D3 in various preparations has been developed. The method is based on a close correlation between the vitamin D3 dose and the content of calcium-binding protein in the duodenal mucosa of rachitic chickens 72 hrs after vitamin D3 administration. Calcium-binding protein is assayed by radial immunodiffusion in agar-agar. The calibration curve of the dose-protein dependence allows measurements of I to 500 IU of vitamin D3 in the sample tested. The method shows good accuracy and reproducibility. The paper presents the results of quantitation of vitamin D in various preparations.