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SOP for Estimation of Sodium (Part 45)

Standard operating/ Working procedure for Estimation of Sodium, Physical and chemical methods of sampling and test for water and wastewater: Part 45 Sodium


When a sodium-containing solution is put into a flame, the brightness of the light passing through it will decrease depending on how much sodium is in the solution. A special lamp that’s made of the same element being measured provides this light.

Detection Limit: 0.1 mg/L


Potassium Chloride Solution: Mix 40 grams of potassium chloride in distilled water to make 1 liter.

Sodium Solution (Stock): Use 1000 mg/L of Sodium Standard Solution as a starting sodium solution.

Standard Sodium Solution: Take different amounts of the stock sodium solution in several 100 ml flasks to create a variety of standard solutions in the working range (0.1, 0.2, 0.3, 0.4, and 0.5 mg/L). Add 10 ml of potassium chloride solution and dilute to 100 ml to have about 2000 µg / L of potassium to suppress ionization while working in air acetylene flame.

Related: SOP for estimation of BORON

Procedure for Estimation of Sodium:

The Methods for the estimation of sodium are as follows:

Preparing the Sample Solution: In a 100 ml beaker, mix 5 ml of concentrated HNO3 with 100 ml of the sample and evaporate until dry. Repeat this twice using the same acid. Dissolve the residue in a small amount of concentrated HCl. Boil, dilute to 50 ml with distilled water, filter, and fill up to 100 ml in a flask.

Creating the Blank Solution: Make suitable blank solutions using the same materials and volumes of distilled water.

Analysis: Follow the procedure. Start by using the blank solution to set the instrument to zero. Use a range of standard solutions and then the sample solution. The sodium concentration in mg/L can be read directly.

Reference: IS 3025 (Part 45): 1993

Related: SOP on Reference Standards and Impurities

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