Cholesterol determinations in serum

When cholesterol, dissolved in acetic acid, is mixed with premixed ferric chloride reagent and heated at 50°C for 15 minutes, a bright pink colour forms which is stable for 1 hour. The reagent contains acetic acid, sulphuric acid, ferric chloride and phosphoric acid, and is stable for years. Sterols extracted from saponified serum by petroleum ether produce an absorbance directly proportional to the cholesterol presenl When whole serum is dissolved in acetic acid and treated with the reagent, the absorbance of the solution is equal to the sum of the absorbance due to cholesterol plus an amount due to other serum components which is constant in healthy persons. By using two reference sera to set up the linear standard curve of absorbance versus cholesterol concentration, a rapid precise method for serum cholesterol is obtained, applicable to healthy persons. The results of this direct method were well in agreement with those from established methods.S. Afr. Med. J. 48, 250 (1974)