Method of Analysis for Di Sodium Edetate

1. Description

A white, crystalline, odorless powder

2. Solubility

Soluble in water, sparingly soluble in ethanol (95%), practically insoluble in chloroform and in the ether

3. Identification

A. The IR absorption spectrum is concordant with the reference spectrum of Disodium Edetate or with the spectrum obtained with Disodium Edetate WRS.

B. Reaction with lead nitrate.

Reagent required
Lead nitrate solution
Potassium iodide solution
2 M Ammonia solution
Procedure: Take 2.0 gms of the sample and transfer it into a 50 ml volumetric flask add 25 ml of water and then add 6 ml of lead nitrate solution. Shake and add 3 ml of potassium iodide solution.
No yellow precipitate is produced.
Make it alkaline to red litmus paper with 2 M ammonia and then add 5 ml of ammonium oxalate solution. No precipitate is produced.

C. Reaction with Calcium chloride

Reagent required
10% w/v calcium chloride solution
2M ammonia solution
Ammonium oxalate solution
Procedure: Take about 0.5 gms of the sample in a test tube and dissolve in 10 ml of water. Add 0.5 ml of 10% w/v calcium chloride solution and make the resulting solution alkaline to red litmus paper with 2M ammonia and add 3 ml of ammonium oxalate solution. No precipitate is produced.

D. Reaction of sodium salts

Reagent required
15% w/v potassium carbonate solution
Potassium antimonate solution
1M acetic acid
Magnesium Uranyl acetate solution.
Procedure: Dissolve 0.1 gm sample with 2 ml water. Add 2 ml of a 15% w/v solution of potassium carbonate and heat to boiling. No precipitate is produced. Now add 4 ml of a freshly prepared potassium antimonate solution and heat to boiling. Allow cooling in ice and if necessary scratch the inside of the test tube with a glass rod. A dense, white precipitate is formed.

5. pH

Limit: Between 4.0 and 5.5
Procedure: Dissolve 0.5 gm of the sample with 50 ml water (Solution A). Transfer Solution A to a 100 ml beaker and measure the pH of a resulting solution.

6. Clarity and color of the solution

Limit: The solution is clear and colorless.

A. Clarity of solution

Reagent required
10% w/v solution of hexamine
Hydrazine sulfate AR
Methanol AR
Reference suspension: Weigh accurately about 1.0 g. of hydrazine sulfate and transfer into a clean and dried 100 ml volumetric flask, dissolve in water and make up volume to 100 ml with water and allow to stand for about 6 hrs. Add 25 ml of this solution to 25 ml of 10% w/v solution of hexamine, mix well and allow to stand for 24 hrs. Mix well and dilute 15 ml of above solution to 1000 ml with water. Dilute 5.0 ml of this suspension (after shaking) to 100 ml with water.
Sample solution: Use solution A as a sample solution.
Procedure: Into separate three Nessler’s cylinder, transfer equal quantity of alcohol, the sample solution and reference suspension such that the Nessler’s cylinders are filled to a depth of 40 mm. After 5 minutes compare the contents of the test tubes against a black background by viewing in diffused daylight.
The sample solution is considered Clear if its clarity is same as that of water or if it is less opalescent than that of the reference suspension OS1.

B. Color of solution

Reagent required
1% w/v Hydrochloric acid
Ferric colorimetric solution (FCS)
Cobaltous chloride colorimetric solution (CCS)
Cupric sulfate colorimetric solution (CSS)
Sample solution: Use sample solution of clarity test.
Reference solution BS8: Dilute 0.4 ml of FCS, 0.4 ml of CCS and 0.2 ml of CSS and with 100 ml of 1% w/v Hydrochloric acid and mix well.
Procedure: Transfer equal volume of the sample solution and reference solution in two different Nessler’s cylinder such that the Nessler’s cylinder are filled to a depth of 40 mm. Compare the color intensity of the sample solution with the reference solution BS8 in diffused daylight against a white background. The sample solution is considered colorless if it has the same appearance as that of water or if it is less intensely colored than reference solution.

7. Heavy metals

Limit: Not more than 20 ppm
Reagent required
Lead standard solution (10 ppm Pb)
Dilute acetic acid
Dilute ammonia solution
Hydrogen sulfide solution
Standard solution: Into a 50-ml Nessler’s cylinder, pipette out 2 ml of the lead standard solution (10 ppm Pb) and dilute with water to 25 ml. Adjust with dilute acetic acid and dilute ammonia solution to a pH between 3.0 and 4.0, dilute with water to about 35 ml and mix.
Test solution: Into a 50-ml Nessler's cylinder, take about 1 gm of the sample and dissolve in 25 ml of water. Adjust with dilute acetic acid and dilute ammonia solution to a pH between 3.0 and 4.0, dilute with water to about 35 ml and mix.
Procedure: To each of the Nessler's cylinders containing the standard solution and the test solution respectively, add 10 ml of freshly prepared hydrogen sulfide solution, mix, dilute to 50 ml with water and allow standing for 5 minutes and viewing downwards over a white surface.
The color produced with the test solution is not more intense than that produced with the standard solution.

8. Iron

Limit: Not more than 80 ppm
Reagent required
20% w/v of iron-free Citric acid solution
Thioglycollic acid
Calcium chloride
Standard solution: Into a 50-ml Nessler's cylinder, take 2.0 ml of the iron standard solution (20 ppm Fe) and dilute it with water up to 10 sample and dissolve it in water and dilute up to 10 ml.
Sample solution: Into a 50-ml Nessler’s cylinder, take 250 mg of the sample and dissolve it in water and dilute up to 10 ml
Procedure: To both the cylinders, add 2 ml of 20% w/v of an iron-free citric acid solution. Add 0.25 gm of calcium chloride to each solution and then add 0.1 ml of Thioglycolic acid, mix, make alkaline with iron-free ammonia solution, dilute to 50 ml with water and allow standing for 5 minutes.
Any color produced in the test solution is not more intense than that produced in the standard solution.

9. Assay

Limit: NLT 98.5% and NMT 101.0%
Procedure: Weigh accurately about 500 mg of the sample into a 500-ml conical flask and dissolve in sufficient quantity of water to produce 300 ml and add 2 gm of hexamine and 2 ml of 2M HCl. Titrate with 0.1M lead nitrate using about 50 mg of Xylenol orange triturate as an indicator. Each ml of 0.1M lead nitrate is equivalent to 0.03722 gm of C10H14N2Na2O8, 2H2O
Calculation
                                                     V x M x F x 100
% Assay Disodium edetate = ----------------------
                                                             W
Where,
V = Consumed volume of 0.1 M Perchloric Acid
M= Molarity of 0.1 M Perchloric Acid
F= Factor
W= Weight of substance