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Potassium-E
Enzymatic Test
METHOD / PRINCIPLE
Potassium is an activator for the enzyme Pyruvate Kinase
(PK). Therefore the kinetic measurement of PK can be
used to determine potassium in serum. The interference
of other activating ions is eliminated by complexing and
decomposition reactions.
REFERENCE RANGE
3.5 - 5.1 mmol/l (13.7 - 19.9 mg/dl)
Note: It is recommended for each laboratory to establish and
maintain its own reference values. The given data are only
an indication.
The procedure is based on the following reaction scheme:
Substrate* + ADP
ANALYTICAL PROCEDURE
PK / K+> Pyruvate + ATP
Pyruvate + NADH + H+
This is the standard procedure, specific Applications
for Analyzers are available upon request.
LDH> Lactate+ NAD+
* Substrate = derivative of phosphoenolpyruvate
The decrease of the absorbance of NADH
is measured at 380 nm; this is proportional to the
concentration of potassium in the sample.
REAGENTS
Wavelength
Temperature
Cuvette
380 nm (380 - 405nm)
37°C
1 cm light path
Read against reagent blank
(RBL)
RBL
Standard
Sample
Reagent R1
200 µL
200 µL
200 µL
Standard
5 µL
Sample
5 µL
Mix well, and incubate for about 5 min, then add
Reagent R2
50 µL
50 µL
50 µL
Mix well, and after 1 min read absorbance A1,
and exactly 3 min later read A2
Constituents (concentrations in the test)
R1:
Good's-Buffer (pH 8.5)
Complexing cryptand
0.5 mmol/l
LDH
< 50 U/ml
NADH
< 10 mmol/l
Stabilizers
R2:
Good's-Buffer (pH 6.5)
Pyruvate Kinase
< 50 U/ml
Stabilizers
A = (A1 – A2) Sample or Standard - (A1 – A2) RBL
Storage and Stability
R1 and R2 are ready for use.
The sealed reagents are stable up to the expiry date
printed on the labels, when stored at 2° to 8°C.
Stability after opening :
At least 3 months
at 2° to 8 °C, if contamination is avoided
On board stability depends very much on the internal
contamination which mostly is different for any analyzer
Do not freeze !
CALCULATION
with standard (Std)
Potassium[mmol / l] 
A sample
 Conc. Std. [mmol / l]
A S tan dard
CALIBRATION & QUALITY CONTROL
For the calibration of automated analyzers Greiner
special calibrator / standard is recommended, for quality
control use Greiner Unitrol-I and -II .
Warnings and Precautions
Reagents contain 0.05% Sodium Azide. Do not swallow
and avoid contact with eyes, skin and mucous membranes.
WASTE
When discarding the reagents, dispose them
according to local or federal regulations.
SAMPLE MATERIAL
Serum (free of hemolysis)
Page 1/2
Greiner Diagnostic GmbH - Unter Gereuth 10 – D-79353 Bahlingen – Germany
www.greiner-diagnostic.com
PERFORMANCE DATA
BIBLIOGRAPHY
1.
- Analytical range
The linear range is up to 8.0 mmol/l. If the obtained
value exceeds this, repeat the test using serum diluted
1+3 with ultra pure water.
Multiply result by 4.
- Lower range
The lower linearity limit is 0.9 mmol/l.
2.
Wu, A.H.B., ed. Tietz, Clin. Guide to Lab.Tests,
4th edition, p.880, W.B.Saunders Co.
M.N. Berry, R.D. Mazzachi, M.Pejakovic, M.J.Peake,
Clin Chem.35/5, p.817-820 (1989)
SYMBOLS USED
- Precision
Within run
n = 50
Sample 1
Sample 2
Average
[mmol/l]
4.62
6.96
SD
[mmol/l]
0.052
0.083
CV
[%]
1.12
1.20
Run to Run
n = 50
Sample 1
Sample 2
Average
[mmol/l]
4.62
6.96
SD
[mmol/l]
0.082
0.123
CV
[%]
1.77
1,77
- Correlation
A comparative study has been performed between the
Greiner test and the ISE method on 50 human serum
samples. The parameters of linear regression are as
follows:
For in vitro diagnostic medical use
Batch Code
Use by
Temperature limitation
Correlation coefficient
r = 0.98
Linear regression
y = 1.07 x - 0.30 mmol/l
INTERFERENCES
- Ascorbic Acid: no interference up to 10 mmol/l
- Bilirubin: no interference up to 20 mg/dL
- Triglycerides: no interference up to 1000 mg/dL
- Hemoglobin: no interference up to 500 mg/dL
- Sodium: no interference up to 150 mmol/l
- Ammonium: no interference up to 0.5 mmol/l
- Calcium: no interference up to 7.5 mmol/l
- Zinc: no interference up to 0.5 mmol/l
- Copper: no interference up to 0.5 mmol/l
Page 2/2
Greiner Diagnostic GmbH - Unter Gereuth 10 – D-79353 Bahlingen – Germany
www.greiner-diagnostic.com