Effect of Solvents on the Absorption Spectrum of Vitamin A

Abstract

IT has long been known that some substances, for example, indigo, yield variously coloured solutions in different solvents. Change of solvent may affect the intensity and position of absorption maxima in the ultra-violet as well as in the visible spectrum. The fact that this phenomenon has been observed with a related substance, carotene, makes it the stranger that various solvents are commonly accepted as interchangeable for the spectrophotometric assay of vitamin A. Thus ethyl alcohol and cyclohexane received equal sanction at the 1934 International Vitamin Conference and in the 1936 “Addendum to the British Pharmacopœia” ; ether is also used in some laboratories, but chlorinated solvents, particularly chloroform, have been regarded with suspicion.