Aluminum Sulfate and Calcium Acetate for Topical Solution
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This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition
Issued and maintained by the United States Pharmacopeial Convention (USP)
1 DEFINITION
Aluminum Sulfate and Calcium Acetate for Topical Solution contains NLT 90.0% and NMT 110.0% of the labeled amounts of aluminum sulfate tetradecahydrate [Al2(SO4)3·14H2O] and calcium acetate monohydrate (C4H6CaO4·H2O).
2 IDENTIFICATION
2.1 A.
Sample: 0.25 g of Aluminum Sulfate and Calcium Acetate for Topical Solution
Analysis: Place the Sample in a test tube. Add 10 mL of water and 0.25 g of calcium carbonate. Heat on a steam bath for 10 min, and filter. Add 3-4 drops of ferric chloride TS to the filtrate. [NOTE-After the addition of the ferric chloride TS, the solution may be heated for 1 min to speed the reaction.]
Acceptance criteria: A reddish-brown color or precipitate indicates acetate.
2.2 B. IDENTIFICATION TESTS-GENERAL, Sulfate (191) andCalcium(191)
Sample solution: Suspend 2 g of sample in 50 mL of water and filter.
Acceptance criteria: Meets the requirements
3 ASSAY
3.1 ALUMINUM SULFATE TETRADECAHYDRATE
Sample solution: Transfer 10 g of Aluminum Sulfate and Calcium Acetate for Topical Solution to a 1000-mL volumetric flask. Add 100 mL of 1.2 N hydrochloric acid and 250 mL of water. Heat on a steam bath or hot plate until dissolved. Cool, and dilute with water to volume. Retain a portion of the Sample solution for the Assay for Calcium Acetate Monohydrate.
Blank: Water
Titrimetric system
Mode : Residual titration
Titrant: 0.02 M zinc sulfate VS
Endpoint detection: Visual
Analysis: Transfer a 5.0-mL aliquot of the Sample solution to a 250-mL conical flask. Add, in the order named, 40.0 mL of 0.01 M edetate disodium VS and 20 mL of acetic acid-ammonium acetate buffer TS, and mix by swirling. Add 50 mL of alcohol and 2 mL of dithizone TS, and titrate the excess 0.01 M edetate disodium VS with Titrant until the color changes from green-violet to a clear rose-pink. Perform a blank titration, substituting 5.0 mL of water for the Sample solution.
Calculate the percentage of aluminum sulfate tetradecahydrate [Al2(SO4)3·14H2O] in the portion of Aluminum Sulfate and Calcium Acetate for Topical Solution taken:
Result = {[D x (VB - VS) x M x F]/W} x 100
D = dilution factor, 1000/5.0
VB = blank titration volume (mL)
VS = sample titration volume (mL)
M = molarity of the Titrant (mmol/mL)
F = equivalency factor, 297.2 (mg/mmol)
W = weight of sample used (mg)
Acceptance criteria: 90.0%-110.0% of the labeled amount of aluminum sulfate tetradecahydrate [Al2(SO4)3·14H2O]
3.2 CALCIUM ACETATE MONOHYDRATE
Sample: Transfer a 5.0-mL aliquot of the Sample solution retained from the Assay for Aluminum Sulfate Tetradecahydrate to a 250-mL conical flask.
Titrimetric system
Mode: Direct titration
Titrant: 0.01 M edetate disodium VS
Endpoint detection: Visual
Analysis: Add 1-2 mL of 50% triethanolamine to mask the aluminum, and mix well. With constant stirring, add to the Sample, in the order named, 100 mL of water, 15 mL of 1 N sodium hydroxide, and 300 mg of hydroxy naphthol blue, and titrate with Titrant. The indicator will change from purple to a clear blue color at the endpoint.
Calculate the percentage of calcium acetate monohydrate (C4H6CaO4·H2O) in the portion of Aluminum Sulfate and Calcium Acetate for Topical Solution taken:
Result = [(D x V x M x F)/W] x 100
D = dilution factor, 1000/5.0
V = sample titration volume (mL)
M = molarity of the Titrant (mmol/mL)
F = equivalency factor, 176.2 (mg/mmol)
W = weight of sample used (mg)
Acceptance criteria: 90.0%-110.0% of the labeled amount of calcium acetate monohydrate (C4H6CaO4·H2O).
4 SPECIFIC TESTS
PH (791)
Sample solution: 1 g of Aluminum Sulfate and Calcium Acetate for Topical Solution in 200 mL of water
Acceptance criteria: 4.0-4.8
5 ADDITIONAL REQUIREMENTS
PACKAGING AND STORAGE: Preserve in single-unit containers, and protect from excessive heat.
