SPECIFICITY OF THE TRIHYDROXYINDOLE METHOD FOR DETERMINATION OF URINARY CATECHOLAMINES*

Abstract

A wave length of 365 m[mu] for excitation of fluorescence in the trihydroxyindole method for urinary catecholamines was shown to be less specific than a wavelength of 405 m[mu]. Of 6000 urines studied, 256 were apparently abnormal when examined using 365 m[mu], but 23 per cent of these were normal when examined with 405 m[mu]. Spectrophoto-fluorometric examination of activation and fluorescence spectra revealed occasional instances of falsely high results, even with 405 m[mu] Further purification of the urine by treatment with ion exchange resin successfully removed the interfering material. Acid hydrolysis occasionally produced nonspecific interfering material. Normal values were obtained both for random samples and 24-hour urine collections. Moderate exercise did not cause any significant increase in catecholamine output.