Aluminum Chlorohydrate
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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)
AIy(OH)3y-zClz · H2O AIy(OH)3y-zClz · 2H2O 210.48
AIy(OH)3y-zClz 174.45
Aluminum chlorohydroxide, dihydrate;
Aluminum hydroxychloride, dihydrate;
Aluminum chlorohydroxide;
Aluminum hydroxychloride;
Dihydrate CAS RN®: 12359-72-7; UNII: HPN8MZW13M.
Anhydrous CAS RN®: 12042-91-0; UNII: 407PSC3OC7.
1 DEFINITION
Aluminum Chlorohydrate consists of complex basic aluminum chloride that is polymeric and loosely hydrated and encompasses a range of aluminum-to-chloride atomic ratios between 1.91:1 and 2.10:1. It contains the equivalent of NLT 90.0% and NMT 110.0% of the labeled amount of anhydrous aluminum chlorohydrate [AIy(OH)3y-zClz].
2 IDENTIFICATION
A. Identification Tests—General, Aluminum〈191〉 and Chloride〈191〉
Sample solution: 100 mg/mL
Acceptance criteria: Meets the requirements
3 ASSAY
3.1 Procedure 1: Content of Chloride
Sample: 700 mg
Titrimetric system
Mode: Direct titration
Titrant: 0.1 N silver nitrate VS
Electrode system: A glass silver–silver chloride electrode and a silver billet electrode system
Endpoint detection: Potentiometric
Analysis: Transfer the Sample to a 250-mL beaker and add 100 mL of water and 10 mL of diluted nitric acid with stirring. Titrate with Titrant and determine the endpoint potentiometrically. Each mL of 0.1 N silver nitrate is equivalent to 3.545 mg of chloride (Cl). Use the chloride content thus obtained to calculate the aluminum:chloride atomic ratio.
3.2 Procedure 2: Content of Aluminum
Edetate disodium titrant: Prepare and standardize as directed in Reagents, Volumetric Solutions, Edetate Disodium, Twentieth-Molar (0.05 M), except use 37.2 g of edetate disodium.
Sample solution: Transfer 200 mg of Aluminum Chlorohydrate to a 250-mL beaker, add 20 mL of water and 5 mL of hydrochloric acid, boil on a hot plate for NLT 5 min, and allow to cool.
Titrimetric system
Mode: Back-titration
Titrant: 0.1 M zinc sulfate VS
Endpoint detection: Visual
Analysis: To the Sample solution add 25.0 mL of Edetate disodium titrant, and adjust with 2.5 N ammonium hydroxide or 1 N acetic acid to a pH of 4.7 ± 0.1. Add 20 mL of acetic acid–ammonium acetate buffer TS, 50 mL of alcohol, and 5 mL of dithizone TS. The pH of this solution should be 4.7 ± 0.1. Titrate the excess edetate disodium with Titrant until the color changes from green-violet to rose-pink. Perform a blank titration, and make any necessary correction. Each mL of 0.1 M Edetate disodium titrant consumed is equivalent to 2.698 mg of aluminum (Al). Use the aluminum content thus obtained to calculate the aluminum:chloride atomic ratio.
3.3 Procedure 3: Aluminum:Chloride Atomic Ratio
Analysis: Use the percentage of aluminum found in the test for Content of Aluminum and the percentage of chloride found in the test for Content of Chloride.
Calculate the aluminum:chloride atomic ratio (X) as follows:
Result = (pAl /pCl ) × (ACl /AAl)
pAl = percentage of aluminum found in Content of Aluminum
pCl = percentage of chloride found in Content of Chloride
ACl = atomic weight of chlorine (Cl), 35.453
AAl = atomic weight of aluminum (Al), 26.98
Acceptance criteria: Between 1.91:1 and 2.10:1
3.4 Procedure 4
Analysis: Calculate the percentage of anhydrous aluminum chlorohydrate [AIy(OH)3y-zClz] in the portion of Aluminum Chlorohydrate taken:
Result = P ({AAl X + [M(3XAl − 1)] + ACl}/AAlX)
PAl = percentage of aluminum as obtained in the test for Content of Aluminum
AAl = atomic weight of aluminum (Al), 26.98
X = aluminum:chloride atomic ratio, as determined in the test for Aluminum:Chloride Atomic Ratio
M = molecular weight of the hydroxide anion (OH), 17.01
ACl = atomic weight of chlorine (Cl), 35.453
Acceptance criteria: 90.0%–110.0% on the anhydrous basis
4 IMPURITIES Change to read:
Arsenic 〈211〉, Procedures, Procedure 1 (CN 1-Jun-2023) : NMT 2 ppm
Change to read:
Limit of Iron
Standard solution: Transfer 2.0 mL of Standard Iron Solution, prepared as directed in Iron 〈241〉, Procedures, Procedure 1 (CN 1-Jun-2023) , to a 50-mL beaker.
Sample solution: Transfer 2.7 g of Aluminum Chlorohydrate to a 100-mL volumetric ask, dilute with water to volume, and mix. Transfer 5.0 mL of this solution to a 50-mL beaker.
Analysis: To each of the beakers containing the Standard solution and the Sample solution, add 5 mL of 6 N nitric acid, cover with a watch glass, and boil on a hot plate for 3–5 min. Allow to cool. Add 5 mL of Ammonium Thiocyanate Solution (prepared as directed in Iron 〈241〉, Procedures, Procedure 1 (CN 1-Jun-2023) ), transfer to separate 50-mL color comparison tubes, and dilute with water to volume.
Acceptance criteria: 150 ppm; the color of the solution from the Sample solution is not darker than that of the solution from the Standard solution.
5 SPECIFIC TESTS
pH 〈791〉
Sample solution: 15 g of Aluminum Chlorohydrate in 100 g of water
Acceptance criteria: 3.0–5.0
6 ADDITIONAL REQUIREMENTS
Packaging and Storage: Preserve in well-closed containers.
Labeling: The label states the content of anhydrous aluminum chlorohydrate.
