Principle
The Present method is based on modification of those
first described by Maruna and Trinder in which sodium
is precipitated as the triple salt, sodium magnesium
uranyl acetate, with the excess uranium then being
reacted with ferrocyanide, producing a chromophore
whose absorbance varies inversely as the concentration
of sodium in the test specimen.

Reagents : Sodium
Reagents I : Filtrate Reagent
Reagents II : Acid Reagent
Reagents III : Sodium Color Reagent

The amount of potassium is determined by using sodium
tetraphenylboron in a specifically prepared mixture to
produce a colloidal suspension. The turbidity of which
is proporational to concentration of K+ in the range of
2-7 mEq/L.

Reagents : Potassium
Reagent I: Potassium reagent
Na⁺/K⁺ Standard : 150/5 mEq/l

Chloride reagent reacts with mercurous thiocyanate to form mercury perchlorate and thiocyanate forms a red complex with ferric ions in the presence of nitric acid.

Reagents : Chloride
Reagent I: Potassium reagent
Chloride Standard : 100 mEq/l

Sample
Freshly drawn non hemolysed serum is the specimen of choice.
Serum Sodium & Potassium are is stable for atleast 24 hours at room temperature and two weeks at 2-8°C. Serum or
heparinised plasma, CSF & Urine. Urine diluted 1+1 with distilled
water can be used for chloride estimation. Chloride in serum is
stable for 7 days at 2-8°C.

Storage & Stability
Store all reagents at room temperature (25-30°C). The reagents are stable until the expiration date as indicated on the label.

Automated Parameters

Test Procedure

Sodium Assay

Filtrate Preparation
Pipette into clean test tubes labelled as Standard(S) and Test(T)

Shake all tubes vigorously and let stand for 5 min, shaking well intermittently. Centrifuge tubes at high speed (2500 to 3000 RPM) for 10 minutes and test supernatant fluids as described below, taking care not to disturb the protein precipitate.

Color Development

Mix well, incubate at R.T. for 5 mins. Measure the absorbance of Std & Test against Reagent Blank at 546 nm.

Calculation
(Abs. of Blank - Abs. Of T) X 150 = Conc. Of Test
________________________
(Abs. Of Blank - Abs. Of Std.)

Procedure Limit
When preparing filtrates, inadequate shaking or centrifugation will cause falsely lowered results.

Test Procedure

Potassium Assay

Mix well and incubate at R.T. for 5 mins. Measure the absorbance of the Standard and Test against Reagent Blank at 630 nm within 15 mins.

Calculation
(Abs. of Test - Abs. Of Blank) X 5 = Conc. Of Test
________________________
(Abs. Of Std - Abs. Of Blank)

Test Procedure
Chloride Assay

Mix well and incubate at R.T. for 5 mins. Measure the absorbance of the Standard and Test against Reagent Blank at 480 nm within 15 mins.

Calculation
(Abs. of Test - Abs. Of Blank) X 100 = Conc. Of Test
________________________
(Abs. Of Std - Abs. Of Blank)

Reference Values
Na : 135 - 155 mEq/l
K : 3.4 - 5.5 mEq/l
Cl : 98 - 110 mEq/l

Linearity
Na : 200 mEq/l
K : 7 mEq/l
Cl : 130 mEq/l

Quality Control
It is recommended that controls be included in each set of assays.

Interferences
Turbid or Icteric serum produce falsely elevated results.

References