Quantitative Analysis by the Variation of the Specific Activity of an Added Radioactive Isotope

Principles of Isotope Dilution Assays

“…Since then, the method has been applied to so wide a variety of compounds and media that justification of a principle based upon synthetic mixtures is no longer necessary. Industrial examples now include vitamins (5), antibiotics (8,4, 81), insecticides (15,26,52), steroids (16), purines (1), and others (11,44,55), to cite selected instances of assays of organic compounds, as well as inorganic analyses such as sul-fate (18) in chromate plating baths, various phosphates in commerical phosphate and detergents (41), zinc in alloys (59), and others (19,58). The isotope dilution assay for cobalamin has been incorporated as a standard method in the first supplement to the U. S. Pharmacopeia XV (63).…”