Quantitative determination of sodium ion
IVD
Store at 2-8ºC
PRINCIPLE OF THE METHOD
Sodium is precipitated with Mg-uranyl acetate; the uranyl ions remaining in
suspension form a yellow-brown complex with thioglycolic acid. The
difference between reagent blank (without precipitation of sodium) and
analysis is proportional to the sodium concentration.
CLINICAL SIGNIFICANCE2
This test is performed when symptoms of a sodium imbalance are present,
or when disorders associated with abnormal sodium levels develop.
Sodium (Na+) is the major positive ion in the fluids outside of cells. The
concentration of sodium inside cells is only about 5 mmol/L compared with
140 mmol/L outside. The sodium content of the blood is a result of a balance
between the amount in the food and beverages you consume, and the
amount your kidneys excrete. (In addition, a small percent is lost through
the stool and sweat.)
Many factors affect sodium levels, including the steroid hormone
aldosterone, which decreases loss of sodium in the urine. ANP (atrial
natriuretic protein) is a hormone secreted from the heart that increases
sodium loss from the body.
Despite the integral relationship between sodium and water, the body
regulates them independent of each other if necessary.
STORAGE AND STABILITY
All the components of the kit are stable until the expiration date on the label
when stored tightly closed at 2-8ºC, protected from light and contaminations
prevented during their use.
Do not use reagents over the expiration date.
Signs of reagent deterioration:
- Precipitating solution becomes discoloured when exposed to the light.
Store protected from light. A slight turbidity does not affect the
determination.
ADDITIONAL EQUIPMENT
- Spectrophotometer or colorimeter measuring at 365 nm.
- Matched cuvettes 1.0 cm light path.
- General laboratory equipment (Note 1, 2, 3).
SAMPLES
- Serum and ammonium or lithium heparin plasma.
QUALITY CONTROL
Control sera are recommended to monitor the performance of assay procedures:
SPINTROL H Normal and Pathologic (Ref. 1002120 and 1002210).
If control values are found outside the defined range, check the instrument,
reagents and calibrator for problems.
Each laboratory should establish its own Quality Control scheme and corrective
actions if controls do not meet the acceptable tolerances.
REFERENCE VALUES1
Serum : 135 - 155 mmol/L
These values are for orientation purpose; each laboratory should establish its own
reference range.
PERFORMANCE CHARACTERISTICS
Measuring range: From detection limit of 49 mmol/L to linearity limit of 300
mmol/L.
If the results obtained were greater than linearity limit, dilute the sample 1/2 with
distilled water and multiply the result by 2.
Precision:
Intra-assay (n=20) Inter-assay (n=20)
Mean (mmol/L) 94,1 155,8 94,2 155,6
SD 2,01 1,39 4,02 5,40
CV (%) 2,13 0,89 4,27 3,47
Analytical sensitivity: 1 mmol/L = 0,0023 A.
Accuracy: Results obtained using SPINREACT reagents did not show systematic
differences when compared with other commercial reagents.
Regression equation: y= 0,883x – 14,123
The results of the performance characteristics depend on the analyzer used.
INTERFERENCES
Hemoglobin does not interfere up to 500 mg/dL, Bilirubin yielded a very low
interference up to 40 mg/dL, and Ascorbic acid equally did not show any effect up
to 20 mg/dL.
NOTES
1. NA-p CAL: Proceed carefully with this product because due its nature it can
get contamined easily.
2. Detergents usually contain high sodium concentrations. The equipment (test
tubes, pipettes, stoppers, cuvettes) must therefore be rinsed carefully with
distilled water. Avoid contamination by traces of sodium.
3. Disposable plastic tubes are recommended for the determination to avoid
contaminations.
