Adaptation of the p-dimethylaminobenzaldehyde method for determining urea concentration in urine is an improved micromechanical method. Accuracy and precision are satisfactory. This method avoids extra steps of deproteinizing or removing normal urinary chromogens

Geiger, P. J.

English

NASA Technical Reports Server

SAugust 1969
	
Brief 69-103 17 
NASA Tech Briefs are issued to summarize specific innovations derived from the U.S. space program, 
to encourage their commercial application. Copies are available to the public at 15 cents each 
from the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Microdetermination of Urea in Urine Using 
p-Dimethylaminobenzaldehyde (PDAB) 
.
The solution: 
Devise an improved microchemical method of 
analysis for urea in urine. 
The solution: 
Adapt the PDAB method for the determination of 
urea in urine to a micro scale. 
How it's done: 
Prepare a standard urea solution by dissolving 
1.500 g of urea in distilled water in a 100 ml volu-
metric flask and diluting to the mark. 
Dissolve 5 grams of analytical reagent grade p-
dimethylaminobenzaldehyde in 100 ml of absolute 
ethanol in a 200 ml volumetric flask. Slowly add 5 
ml of concentrated sulfuric acid with swirling and 
cool to room temperature. Add distilled water to 
the mark. Store this PDAB reagent at room tem-
perature in an amber bottle in the dark when not 
in use. It is relatively stable for many months. 	 - 
Prepare a blank by micropipetting 0.01 ml of dis-
tilled water into a tube, adding 5 ml of PDAB re-
agent, and mixing well two or three times on a vortex 
mixer. In separate tubes, repeat this procedure using 
the standard urea solution and the urine sample in 
place of distilled water. Allow the tubes to stand 
for 10 minutes. Put the blank in a one-cm stoppered 
cuvette and read absorbance in a spectrophotometer 
set at a wavelength of 435 nm and 0.02 mm slit 
width. Repeat the above step for the standard urea 
solution and the urine sample, respectively, and cor-
rect each for the blank. 
A stable color develops when PDAB reagent is 
mixed with the standard urea solution or the urine
sample. This color is proportional to the urea con-
tent. The concentration of urea in the urine sample 
is calculated by dividing the absorbance of the 
urine sample by the absorbance of the standard, and 
multiplying by the concentration of urea in the 
standard. 
Beer's law is obeyed over the entWe range of best 
photometric accuracy in the spectrometer. Readings 
greater than 0.9 or less than 0.1 absorbance would 
indicate that the colored solution must either be di-
luted by adding more PDAB reagent or the sample 
size increased to retain the best photometric accuracy. 
This microchemical adaptation of the PDAB 
method avoids extra steps of deproteinizing or re-
moving normal urinary chromogens, which are re-
quired by other adaptations of the method, except 
under unusual circumstances where interference from 
excess protein occurs or when a sulfa drug or p-
aminosalicylic acid (PAS) is present. In the event 
of protein interference, a stable tungstic acid may 
be used for deproteinizing the urine sample. Inter- 
ference from a sulfa drug or PAS can be detected 
or removed. 
Note: 
Accuracy and precision of the microchemical 
adaptation of the PDAB method for determining 
urea in urine are satisfactory. The use of 0.01 
ml samples rather than 0.2 to 2.0 ml samples 
required by other adaptations of the method is an 
advantage. It should be adaptable with ease to 
automated analysis.
(continued overleaf) 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States 
Government nor any person acting on behalf of the United States
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19690000316 2020-03-16T18:09:48+00:00Z
2. Clinical laboratories, drug companies, hospitals, 
doctors, veterinarians, pharmacologists, toxicolo-
gists, and biochemists may be interested in this 
information. 
3. Documentation is available from: 
Clearinghouse for Federal Scientific 
and Technical Information 
Springfield, Virginia 22151 
Price $3.00 
Reference: TSP69-10317 
Patent status: 
No patent action is contemplated by NASA. 
Source: P. J. Geiger 
NASA Pasadena Office 
(NPO-10715) 
Brief 69-10317	 Category 04
S 


Microdetermination of urea in urine using p-dimethylaminobenzaldehyde /PDAB/

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