A discrepancy between biological assays and other methods of determining vitamin A. I.

Abstract

THREE methods are at present widely used for the determination of vitamin A, viz. (i) the fundamental method of biological assay, (ii) the measurement of the ultraviolet absorption at 328m,, and (iii) the evaluation of blue-colour intensity in the antimony trichloride test. The colour test and the ultraviolet absorption owe their origin to the alcohol C20H29OH or its esters Refinement of all three methods has, however, revealed discrepancies, and the object of this paper is to show that some materials possess biological activity, indistinguishable from that of 0i