Photoelectric spectrophotometry applied to the analysis of mixtures, and vitamin A oils

Studies in vitamin A. 9. The role of the thyroid in carotene and vitamin A metabolism

“…In order to see if any other possible vitamin A derivatives absorbing in the region 300-360 mA. were present the Morton & Stubbs (1946) procedure was applied; a typical result is recorded in Fig. 1.…”

Studies in vitamin A. 12. Whale-liver oil analysis: preparation of kitol esters

“…; gross) was 28-7 and the net contribution due to vitamin A was 14-14 + 3-02 = 17-16. The simple correction procedure of Morton & Stubbs (1946) gave 15-8-a figure which is significantly low.…”

“…A measured volume ofsolution A was diluted with ethanol and showed Am., 326 miu., El % 135-8 (corrected by the Morton & Stubbs (1946) Table 4). Kaplansky & Balaba (1946) claimed that ,-carotene in colloidal solution when incubated with either thyroglobulin or iodinated casein was converted into vitamin A in good yield; a typical experiment resulted apparently in the production of 60 ug.…”

“…At an early period in the history of the use of whale-liver oils as a source of vitamin A a commercial concentrate was studied (Edisbury et al 1935(Edisbury et al , 1937 It speedily emerged in these laboratories, and in those of Lever Brothers and Unilever Ltd. at Port Sunlight, that neither the colour test nor the ultraviolet absorption was anomalous in a constant fashion, and the basis for the empirical use of a conversion factor of 1200 instead of 1600 (widely used for fish-liver oils) disappeared. The correction procedure ofMorton& Stubbs (1946) was often stretched beyond the limits of its utility by the magnitude of the irrelevant absorption. It had also become clear that the factor of 1600 was itself a reflexion of the fact that, on the average, fish-liver oils exhibited some 11 % or so of 'irrelevant' absorption and that a factor of 1800 was appropriate to preparations in which vitamin A was the only significantly absorbing entity (Morton & Stubbs, 1947 light petroleum).…”

“…On the other hand, if kitol were found to be a normal constituent of whale blood and milk the suggestion would need to be reconsidered. according to the procedure of Morton & Stubbs (1946). The curve (Fig.…”