0.004 M Benzethonium Chloride Solution Preparation and Standardization Procedure

The preparation and standardization of 0.004M Benzethonium chloride solution constitute an important analytical procedure in pharmaceutical quality control laboratory.

1.0 Scope: This procedure is applicable for Preparation and Standardization of 0.004 M benzethonium chloride solution.

2.0 Apparatus:

• Auto titrator
• 1000 ml and 100 ml volumetric flask
• 250 ml glass-stoppered, conical flask
• 10 ml volumetric pipette

3.0 Reagents:

• Benzethonium chloride AR grade
• Anhydrous sodium carbonate
• Mercuric acetate solution
• Anhydrous glacial acetic acid.
• 0.1M perchloric acid solution
• Crystal violet solution

Preparation of reagents:

Crystal violet solution:

Dissolve 0.5 g of crystal violet in a 50 ml of anhydrous glacial acetic acid to produce 100 ml with anhydrous glacial acetic acid and store in a well fitted transparent glass bottle.

0.1M perchloric acid solution:

Prepare solution as per SOP on “0.1M perchloric acid solution”.

Mercuric acetate solution:

Dissolve 5 g of mercuric acetate in a 50 ml anhydrous glacial acetic acid to produce 100 ml with anhydrous glacial acetic acid and store in a well fitted transparent glass bottle.

4.0 Preparation:

Dissolve 1.792 g of benzethonium chloride, previously dried to constant weight at 105 °C, in sufficient purified water to produce 1000 ml.

5.0 Standardization:

• Dissolve 0.35 g of the dried benzethonium chloride in 30 ml of anhydrous glacial acetic acid.
• Add 6 ml of mercuric acetate solution and titrate with 0.1M perchloric acid potentiometrically by the auto titrator using 0.05 ml of crystal violet solution as indicator.
• Perform a blank determination and make any necessary correction.

Each ml of 0.1M perchloric acid is equivalent to 0.04481 g of C₂₇H₄₂CINO₂.

6.0 Calculation:

N = W x 0.004
——————
V x 0.04481

Were:
N = molarity of 0.1M perchloric acid solution
W = weight of benzethonium chloride in g
V = volume 0.1M perchloric acid solution in ml

7.0 Storage:

Store in a well-fitted transparent glass bottle.

8.0 Reference:

As per IP –96 Page No. A-210