A new, rapid fluorometric determination of retinol in serum

A new procedure for the determination of retinol (vitamin A alcohol) in blood has been devised. It consists of direct measurement of the fluorescence of retinol (excitation 335 nm.; emission 458 nm.) in diluted serum, and is considerably more rapid than any previous method. Such measurements are feasible because the intensity of fluorescence of retinol bound to its transport protein (retinol-binding protein) is sufficiently high that other natural occurring fluorescent substances in blood do not interfere significantly. When the new method was compared to a conventional procedure employing extraction and chromatographic separation of retinol on columns of alumina, the correlation coefficient was 0.85.