Assay of Calcium Gluconate

Assay of Calcium Gluconate by Complexometry

Aim: To perform the assay of calcium gluconate by complexometry. 

Requirement: 

• Apparatus: Beaker, Funnel, Pipette, Burrette. 
• Chemicals: Magnesium sulphate, Strong ammonia solution, Calcium gluconate. 

Monograph:

• C₁₂H₂₂CaO₁₄H₂O 
• Molecular weight 448.4 
• Calcium gluconate is a calcium o-gluconate monohydrate. 
• Calcium gluconate contains not less than 98.5 per cent and not more than 102.0 per cent of C₁₂H₂₂CaO₁₄H₂O. 
• Category: Calcium replenisher. 
• Dose: Orally, up to 15 g daily, in divided doses. By intramuscular or slow intravenous injection, 1 to 2 g (500 mg of calcium gluconate is approximately equivalent to 2.3 mmol of Ca²⁺). 
• Description: A white, crystalline powder or granules. 

Procedure:

(A) Standardisation of Disodium EDTA:  Preparation of disodium EDTA (0.1 M): Dissolve 37.2 g of disodium EDTA in sufficient water to produce 1000 ml. 

Procedure:  Weigh accurately about 0.8 g of granulated zinc, dissolve by gentle warming in 12 ml of dilute hydrochloric acid and add 0.1 ml of bromine water. Boil to remove excess bromine, cool and add sufficient water to produce 200.0 ml. Pipette out 20.0 ml of the resulting solution into a flask and nearly neutralize with 2 M sodium hydroxide. Dilute to about 150 ml with water, add sufficient ammonium buffer of pH 10.0 to dissolve the precipitate and add 5 ml in excess. Add 50 mg of Mordant Black II mixture and titrate with disodium EDTA solution until the solution turns green. 

1 ml of 0.1 M disodium EDTA is equivalent to 0.000654 g of Zn.

(B) Assay:  Weigh accurately about 0.5 g and dissolve in 50 ml of warm water; cool, add 5.0 ml of 0.05 M magnesium sulphate and 10 ml of strong ammonia solution and titrate with 0.05 M disodium EDTA using mordant black II mixture as an indicator. From the volume of 0.05 M, disodium EDTA is required to subtract the volume of magnesium sulphate solution added. 

1 ml of the remainder of 0.05 M disodium EDTA is equivalent to 0.02242 g of C₁₂H₂₂CaO₁₄H₂O.

Observation table: (Standardization)

Sr. No.	Parameters	Reading
1.	Burette solution	Disodium EDTA
2.	Conical flask solution	Ammonium buffer, Granulated zinc
3.	Indicator	Mordant Black II
4.	Endpoint	Green

Burette reading B.R (ml)	Trial 1	Trial 2	Trial 3	Average (BR)

Observation table: (Assay)

Sr. No.	Parameters	Reading
1.	Burette solution	Disodium edetate
2.	Conical flask solution	Magnesium sulphate, Strong ammonia solution
3.	Indicator	Mordant Black II
4.	Endpoint	Deep blue

Burette reading B.R (ml)	Trial 1	Trial 2	Trial 3	Average (BR)

Result: The % purity of calcium gluconate is …….

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