A Rapid and Specific Ultramicro Method for Total Serum Cholesterol

Abstract

Abstract A modification of the Zak cholesterol reaction is described in which ethanol is substituted for glacial acetic acid. This modification avoids the hazard of purifying glacial acetic acid and also increases the specificity of the reaction by eliminating interference from bromide or iodide salts. The ethanolic reaction has the absorbance spectrum, sensitivity, and stability of the usual acetic acid reaction. A rapid ultramicro method has been developed based on this ethanolic reaction. A 0.01- to 0.05-ml. sample of serum is extracted with 2.5 ml. of ethanol, and a 2.0-ml. aliquot of this extract is reacted directly with 2.0 ml. of a Zak color reagent. Cholesterol concentrations as determined by this procedure and by the Sperry-Webb method showed satisfactory agreement for monkey and human sera, including normal, hemolyzed, high cholesterol, and severely lipemic or jaundiced sera..