Differential absorption spectrophotometric technique, using murexide, gives a highly precise analysis of calcium in volumes of blood serum as small as 0.01 ml. The method of additions and proper timing allows compensation to be made for fading, variation in type of serum or plasma, and aging of the specimen

Holtzman, R. B.

Ilcewicz, F. H.

English

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June 1969	 Brief 69-10160 
.	
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US
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the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Rapid and Precise Analysis for Calcium in Blood Serum 
.A simple, precise, and accurate method for deter-
mining the level of calcium in blood serum was re-
quired that needed only microquantities of the sam-
ples. Volumetric titrations, the standard methods for 
such determinations, require large samples and a fair 
amount of manipulation; more-recent methods by 
atomic-absorption spectrophotometry, although rapid 
and accurate, require large samples, and the serum 
protein clogs the jets. 
.
A differential-absorption spectrophotometric tech-
nique has been developed that, using murexide, gives 
a highly precise analysis of calcium in volumes of 
serum as small as 0.01 ml. The method of additions 
and proper timing allows compensation to be made for 
fading, variation in type of serum or plasma, and 
aging of the specimen. The method is very rapid, 
especially for large numbers of samples; precision and 
accuracy are about 1.5%. 
The levels of calcium are measured on a double-
beam recording spectrophotometer with 1.0-cm silica 
cells. The indicator solution contains murexide at 0.1 
mg/ml in a mixture of 2% water in propylene glycol. 
The optical density is used as a check on the concen-
tration of the dye; 1.5 ml of indicator in 2.5 ml of 
0.044M KOH, compared to a reference cell containing 
H20, should read approximately 1.4 absorbance units 
(A), at 545 m, 5 minutes after addition to the KOH 
solution. The working calcium standard is the stock 
solution diluted 1:10 with water to give a calcium 
concentration of 0.1 g/Iiter. The calcium concentra-
tion of the diagnostic reagent is 10.5 mg%. 
In the analysis, 2.50 ml of 0.044M KOH is pip-
etted into two 7-ml self-capping polyethylene vials. A 
10:1 to 15:1 sample is pipetted into one of the vials,
and the pipette is rinsed with the contained solution. 
The murexide indicator (1.50 ml) is added to both 
vials in rapid succession with a commercially avail-
able Repipet dispensing unit; then the solutions are 
mixed by repeated inversions slow enough to avoid 
foaming. 
The solutions are then placed in clean, dry cells 
before the absorption peak of the sample solution is 
read against the reagent blank at 497 m, 5 minutes 
after addition of the dye. The ratio of absorption by 
the sample to absorption by an equal volume of stand-
ard calcium solution (0.1 g/liter), multiplied by 10, 
equals the concentration of calcium in the sample (in 
milligrams percent). The rapidity of operations allows 
three samples and a reagent blank to be dispensed 
and run at 1-minute intervals without loss of accuracy. 
Reference: 
1. F. H. Ilcewicz and R. B. Holtzman, ANL-7360 
(Argonne National Laboratory, Argonne, 111., June 
1967), p. 89. 
Notes: 
I. Medical laboratories, hospitals, and blood centers 
may be interested in this information. 
2. Inquiries may be directed to: 
Office of Industrial Cooperation 
Argonne National Laboratory 
9700 South Cass Avenue 
Argonne, Illinois 60439 
Reference: B69-10160 
Source: F. H. Ilcewicz and R. B. Holtzman
Radiological Physics Division
(ARG-10246) 
(continued overleaf) 
This document was prepared under the sponsorship of the Atomic 
Energy Commission and/or the National Aeronautics and Space 
Administration. Neither the United States Government nor any per-
son 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 the use of any information, apparatus, 
method, or process disclosed in this document may not infringe pri-
vately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19690000160 2020-03-16T17:40:18+00:00Z
Patent status: 
Inquiries concerning rights for commercial use of 
this innovation may be made to: 
Mr. George H. Lee, Chief 
Chicago Patent Group 
U.S. Atomic Energy Commission 
Chicago Operations Office 
9800 South Cass Avenue 
Argonne, Illinois 60439
is 
. 
Brief 69-10160
Category 04


Rapid and precise analysis for calcium in blood serum

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