Table 1 . Relative Fluorescence of Some Sterols

Sensitive or simple methods for the rapid determination of cholesterol in biological fluids have been developed during the past 10 years. Sensitivity has been increased by fluorimetry of the Lieberman-Burchard reaction for cholesterol. Measurement of the reaction of cholesterol with ferric chloride is simpler. Still, there are great differences between the results when different methods are used to measure the microquantities of cholesterol present in small volumes of serum or cerebrospinal fluid. In the proposed method, the simpler ferric chloride technique has been made highly sensitive by use of fluorometry. As little as 100 il of cerebrospinal fluid, containing less than 1 g of cholesterol, my be used, and the reaction is stable for as long as 1 h. Interference was negligible from pigments (such as bilirubin and hemo. globin), certain drugs, and ionic substances that might be expected to affect fluorescence.