The micro-determination of urea in blood and other fluids

Abstract

A method was described for the accurate estimation of urea in 0.2 ml. blood. The urea was precipitated with xanthydrol and the dixanthylurea precipitate estimated colorimetrically. The reaction was specific for urea, and ammonia did not interfere with the detn. Blood ureas varying from 10 to 500 mgm. per 100 ml. may be estimated to within [plus or minus] 3% without altering the conditions. Urea in urine, suitably diluted, was detd. by exactly the same technique. 3 methods for blood urea detn. depending upon the use of urease were studied and their relative advantages and disadvantages were discussed. A series of 18 blood samples of varying urea concentration were analysed by all 4 methods, and the results compared.