Spectrophotometric Determination of Urea in Natural Waters with Hypochlorite and Phenol

摘要

A yellow compound formed from urea, hypochlorite, and phenol with an absorbancy maximum at 454 millimicrons has been adapted to determine micromolar quantities of urea in natural waters. The urea is chlorinated in a solution of sodium hypochlorite at pH 7.7, and upon the addition of phenol, the intermediate condenses rapidly to form the colored product. In freshwater, the absorbancy index is 2600 absorbancy units per centimeter cell times gram atom urea-N per liter, and in 35 parts per thousand seawater, the color is twice as intense. The lower limit of detection of urea in seawater is 0.2 microgram atoms urea-N per liter, and the relative standard deviation is 10% at a urea-N concentration of 1 microgram atom per liter. An adaptation of the method to automatic analysis of clinical samples is suggested, and a sensitive analysis procedure for tyrosine is described. (Author)