SOP for ESTIMATION OF SODIUM AND POTASSIUM BY AAS

PRINCIPLE:

  The Copper content of the sample is determined by Atomic Absorption Spectrophotometry. For total recoverable copper, an acid digestion procedure is carried out prior to aspiration of the sample.

 Limit of Detection: 0.02 mg/L

REAGENTS

1. Hydrochloric acid – Concentrated 

2. Nitric acid : Concentrated

3. Nitric acid : (1:500)

4. Dilute sulfuric acid : 1:1

5. Copper stock solution: Merck 1000 mg/L NIST Certified Reference Material or Dissolve 1 g of pure Copper metal in 30 ml (1:1) nitric acid and add 4 ml of (1:1) sulfuric acid and heat until sulfur trioxide fumes evolve. Cool the solution and dilute to 1 litre with distilled water (1 ml = 1 mg of Cu).

PROCEDURE

Preparation of Standard solution: Prepare a reagent blank and a series of 100 ml standards containing 0.2, 0.4, 0.6, 0.8 and 1.0 mg/L of copper by diluting a suitable volume of the standard solution with dilute nitric acid.

Sample preparation: Transfer 1000 ml well-mixed sample to the evaporation dish and add 3 ml nitric acid. Heat and evaporate to 20 ml (do not boil). Cool and add 3 ml nitric acid and heat until digestion is complete. Add 2 ml HCl (1:1 v/v) and heat gently to dissolve the residue. Wash the evaporation dish for 3 to 4 times with water and filter. Wash the filter and discard. Dilute the filtrate & make up 100 ml volume with water.

(10 times concentrate the sample)

Analysis: Operate the instrument as per SOP. Aspirate nitric acid (1:500) as blank. Then aspirate series of standards and then aspirate the sample solution. Read the concentration in mg/L of copper directly.

(Apply the dilution factor 0.1 because the sample is concentrate 10 times)

REFERENCE: IS 3025 (Part 42): 1992