Abstract
THE three approved methods of estimating vitamin A content give different results, according to A. L. Bacharach, Prof. J. C. Drummond and Dr. R. A. Morton. The values obtained by the spectroscopic method are at variance with those obtained by biological assay; the subsidiary standard (the U.S. Pharmacopoeia reference oil) has deteriorated, as shown by both fall in absorption coefficient and by biological tests; even the direct biological comparison with the international standard preparation is apparently liable to variations of 20-100 per cent.
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Points from Foregoing Letters. Nature 137, 154 (1936). https://doi.org/10.1038/137154c0
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DOI: https://doi.org/10.1038/137154c0