SERUM SODIUM AND POTASSIUM VALUES IN FOUR HUNDRED
NORMAL HUMAN SUBJECTS, D E T E R M I N E D BY T H E BECKMAN
FLAME PHOTOMETER*
HOWARD C. ELLIOTT, JR., B.S., AND HOWARD L. HOLLEY, M.D.
From the Departments of Biochemistry and Medicine, Medical-Dental Schools of Alabama,
Birmingham, Alabama
Recently, there have been several publications 5,7 regarding the use of the
Beckman Flame Photometer for the quantitative determinations of sodium
and potassium in biological material. This report is concerned with statistical
studies of sodium and potassium values in normal human subjects, together
with a correlation of these findings with those of other workers. Four hundred
serum samples from normal subjects were examined by the technic described by
Mosher. 5
PROCEDURE
The normal samples were obtained from fasting volunteers at the blood
bank of the Jefferson-Hillman Hospital, who were fairly evenly distributed in
sex and age. The blood was collected in plastic tubes, allowed to clot and centrifuged immediately to prevent any shift in the electrolyte equilibrium between
cells and serum. It was decided to use serum obtained from clotted blood in place
of plasma because of the difficulty in obtaining heparinized blood in a charity
hospital, and the possibility of contamination with sodium or potassium if
oxalates were used. The macro technic described by Mosher5 was used with the
exception of the following change. The stock standard was prepared to contain
145 mEq. of sodium and 5.0 mEq. of potassium per liter, and 0.8, 1.0 and 1.2
ml. of this solution were transferred by a microburet into 50-ml. volumetric
flasks to form the low, middle and high standards. Within the limits set by these
standard solutions the transmission-concentration relationship is linear. This
makes possible calculation of results by simple proportionality. If a sample did
not fall within the limits of the above standards another serum dilution was
made and the determination repeated.
Duplicate determinations were made, and the average of two readings on each
determination was taken as the correct reading. The experimental error of the
technic was studied, using the following procedure. Five samples of pooled
serum were placed in separate tubes and placed with five clinical samples. These
were numbered by a disinterested person and then given to the analyst, who thus
had no idea what the samples were. This completely eliminated the psychological
* A portion of this material has been extracted from the thesis of Howard C. Elliott, J r . ,
presented in partial fulfillment for the degree of Master of Science, Medical College of
Alabama, Birmingham, Alabama.
This study was supported in part by a grant from Lakeside Laboratories, Inc., Milwaukee, Wisconsin.
Received for publication, May 21, 1951.
831
832
ELLIOTT AND HOLLEY
effect of doing repeated determinations on the same sample. Table 1 is typical of a
series of these studies, and shows the reproducibility of the technic when performed by an experienced technician.
A number of sodium and potassium determinations were made, using both
the flame photometric technic and established methods of chemical analysis. 3 ' 5 ' 8
The results are indicated in Table 2.
TABLE 1
A N A L Y S I S OF P O O L E D S E R U M S
SAMPLE
la
lb
Ic
Id
Ie
Average
SODIUM
DEV.
AV. DEV.
POTASSIUM
DEV.
AV. DEV.
mEq./l.
mEq./l.
% of m.
mEq./l.
mEq./l.
% of av.
140.4
141.0
143.3
142.9
143.3
1.8
1.2
1.1
0.7
1.1
1.3
0.8
0.8
0.5
0.8
4.34
4.35
4.30
4.24
4.28
0.04
0.05
0.00
0.06
0.02
0.9
1.2
0.0
1.4
0.5
142.2
1.2
0.86
4.30
0.034
0.79
TABLE 2
COMPARISON O F V A L U E S O F SODIUM AND POTASSIUM IN S E R U M BY C H E M I C A L AND
F L A M E PHOTOMETRIC ANALYSIS
SOD ITJ M
POTASSIUM
SAMPLE
1
2
3
4
5
6
7
8
9
10
Chem.
Fl. Ph.
Chem.
l"i. Ph.
mEq./l.
mEq./l.
mEq./l.
mEj./l.
144.1
147.0
141.6
151.3
149.9
138.2
144.7
147.6
142.2
146.0
142.3
149.2
141.0
152.1
147.5
138.5
143.1
148.9
141.0
148.3
5.4
5.1
7.0
4.8
4.9
4.1
4.7
5.3
4.9
6.9
4.S
4.6
6.1
4.6
4.5
3.S
4.0
4.4
4.3
6.3
RESULTS OF THE•NORMAL DETERMINATIONS
The distribution curves (Figures 1 and 2) for both sodium and potassium
compare well with hypothetical "normal" distribution curves. In the 400 sodium
determinations shown in Figure 1 the range is from 135.0 to 155.0 mEq./l.,
with an average value of 144.7 mEq./l. The standard deviation is 3.81 mEq./l.,
and the coefficient of variation is 2.6 per cent. Two hundred and eighty determinations, or 70 percent of the sodium values, fall within the mean ± the standard
deviation. The 400 potassium determinations shown in Figure 2 indicate a
distribution very slightly skewed to the right. The range of the potassium
SERUM SODIUM AND POTASSIUM
833
determinations is from 3.1 to 5.5 mEq./l., with an average of 4.18 mEq./l. The
standard deviation is 0.43 mEq./l., and the coefficient of variation is .10.3 per
cent. Two hundred and seventy-four, or 68.5 per cent of the potassium values
80
70
co60
§50
§40
co
&30
o20
z
135 136-7 138-9 110-1 I42"3 144-5146-7 146-9 150" I 152" 3 I54"5
SODIUM
mEQ/L
FIG. 1. Distribution of flame photometric determinations of serum sodium in 400 normal persons.
90
80
SUBJECTS
70
60
50
40
fc 30
b 20
z
10
31 32-334-5 3£\73B-.940-l 4?:3 44"54.6"7 48-9 50".1 52:35.4:5
POTASSIUM
mEQ/L
FIG. 2. Distribution of flame photometric determinations of serum potassium in 400 normal persons.
fall within the range of the mean ± standard deviation. The ranges covered
by one standard deviation in the sodium and potassium determinations are in
accordance with Arkin and Colton,1 who state that 68.26 per cent of the values
should be covered by the mean =fc one standard deviation in a normal distribution curve.
834
ELLIOTT AND HOLLEY
DISCUSSION
The results of the sodium and potassium determinations by both chemical
and flame photometric technics, as shown in Table 2, indicate that sodium
values are the same within the limits of experimental error by both methods,
while lower potassium values are obtained with flame photometric determinations than by chemical analysis. We feel that a greater degree of precision is
possible with flame photometric technics, and accept these values.
TABLE 3
STATISTICAL ANALYSIS OP D A T A O B T A I N E D BY F L A M E PHOTOMETRY
Average
Range
Standard deviation
Coefficient of variation
Average deviation
Deviation per cent average
SODIUM
POTASSIUM
mEq./l.
mEq./l.
144.7
135.0-155.0
3. SI
2.6
1.91
1.3
4.IS
3.1-5.5
0.43
10.3
.31
7.4
TABLE 4
COMPARISON O F STATISTICAL D A T A BY VARIOUS INVESTIGATORS
INVESTIGATOR
NO. DETNS.
AV.
RANGE
DEV.
142.0
144.0
153
136-158
135.5-153.2
140-159
130-145
(av.) l . S
(St.) 3.6
4.06
4.52
5.1
3.61-4.S5
3.6-6.2
3.6-7.2
4.2-4.9
Sodium
mEq./l.
Smith 5
Marin is 3 .. .
Overman 4 .
Hald 2 . . . .
70
107
30
Potassium
Smith*. . .
Marinis 3 ..
Overman 4
Hald2....
73
107
30
(av.)
(St.)
26
45
Table 3 shows the statistical analysis of the data we have obtained with the
Beckman Flame Photometer, and Table 4 is a compilation of the other published statistics • ' ' on normal sodium and potassium determination by
flame photometry. Smith, and co-workers7 are the only other investigators who
have used the Beckman Flame Photometer and reported values obtained. While
our range of. sodium values is somewhat greater, this is to be expected in consideration of the number of samples involved in each case. The average values
and deviations compare favorably with Smith and associates,7 and with Marinis,4
who used the Perkin-Elmer Flame Photometer. In the potassium values there is
835
SERUM SODIUM AND POTASSIUM
some deviation in the range compared with other investigators, but, again, the
average values and deviations are the same order of magnitude. The potassium
values we found would also indicate that the normal values for potassium are
below commonly accepted figures as stated by Smith and associates.7
Possibly the correlation is not as great with Hald 2 and Overman 6 because of
the small number of samples they analyzed, and refinements in instruments and
technics since their work was published.
The statistical study of the data by separation into sexes, age groups, and race
showed no significant deviation, and is not included in this study.
SUMMARY
It has been shown that the technic of Mosher1 is reproducible, and values
obtained are in agreement with other investigators, 2 ' 4 ' 6' 7 using flame photometric technics. The average value for sodium is in agreement with values reported by previous workers. The average value for potassium falls significantly
below that reported by previous workers, but is in agreement with Smith.7
REFERENCES
1. A R K I N , H., AND COLTON, R . R . : An Outline of Statistical Methods, E d . 4. New York:
Barnes and Noble, Inc., p . 3S.
2. H A L D , P . M . : The flame photometer for t h e measurement of sodium and potassium in
biological fluids. J . Biol. Chem., 167: 499-510, 1947.
3. LOON BY, J. M., AND D Y E R , C. G.: A photoelectric method for the determination of potassium in blood serum. J . Lab. and Clin. Med., 28: 355, 1942.
4. M A K I N I S , T . P . , M U I R H E A D , E . E . , J O N E S , F . , AND H I L L , J . M . : Sodium and
potassium
determinations in health and disease. J . L a b . and Clin. Med., 32: 1208-1216, 1947.
5. M O S H E R , R . E . , B O Y L E , A. J., B I R D , E . J., JACOBSON, S. D . , BATCHELOR, T . M., I S K R I ,
L.T., AND M Y E R S , G. B . : The use of flame photometry for t h e q u a n t i t a t i v e determination of sodium and potassium in urine. Am. J . Clin. P a t h . , 19: 461-470, 1949.
6. OVERMAN, R. R., AND D A V I S , A. K . : The application of flame photometry t o sodium and
potassium determinations in biological fluids. J. Biol. Chem., 168: 641-649, 1947.
7. S M I T H , R . G., C R A I G , P., B I R D , ID. J., BOYLE, A., I S E R I , L . T . ,
JACOBSON, S. D . , AND
M Y E R S , G. B . : Spectrochemical values for sodium, potassium, iron, magnesium and
calcium in normal human plasma. Am. J. Clin. P a t h . , 20: 263-272, 1950.
S. WEINBACH, A. P . : A micromethod for t h e determination of sodium. J . Biol. Chem.,
110: 95, 1935.