Spectrophotometric study of influences on the direct ferric perchlorate method for the determination of serum cholesterol

A spectrophotometric study of several influences on a direct colorimetric determination of serum cholesterol has been described. Interferences of in vitro and in vivo types were considered, and it was found that certain compounds such as bromide, uracils, and bilirubin could exert both positive and negative interfering influences on the reaction of ferric perchlorate with cholesterol in an ethyl acetate-ethanol-sulfuric acid medium. Some interferences such as bilirubin are noncompeting side reactions which are absolute in their interference capabilities, while others such as the uracils and bromide have an entirely different influence. In the latter circumstance, the fine structures of spectra are altered by a nonadditive phenomenon of the reactant and hyperchromic (bromide), and hypochromic (uracils) effects take place which appear to result in relative rather than absolute errors.