Quantitative determination of cholestanol in plasma with mass fragmentography. Biochemical diagnosis of cerebrotendinous xanthomatosis.

A simple, sensitive, and accurate method for determination of cholestanol in plasma is described. In this method a fixed amount of cholestane is added to 1 ml of plasma as an internal standard and steroids are saponified and extracted with n-hexane. The amounts of cholestanol and cholesterol are determined by mass fragmentography by monitoring the intensities of m/e 306, m/e 329, and m/e 372 fragment ions. The relative standard deviation of results for cholestanol was about 6.3%. The cholestanol concentrations in the plasma, erythrocyte stroma, and plasma lipoproteins of three patients with cerebrotendinous xanthomatosis were determined by this method.