Aluminum Hydroxide Gel
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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)
Al(OH)3 78.00
Aluminum hydroxide.
Aluminum hydroxide CAS RN®: 21645-51-2.
Aluminum Hydroxide Gel is a suspension of amorphous aluminum hydroxide in which there is a partial substitution of carbonate for hydroxide. It contains the equivalent of not less than 90.0 percent and not more than 110.0 percent of the labeled amount of aluminum hydroxide [Al(OH)3]. It may contain Peppermint Oil, Glycerin, Sorbitol, Sucrose, Saccharin, or other suitable flavors, and it may contain suitable antimicrobial agents.
Packaging and storage-Preserve in tight containers, and avoid freezing.
Identification-
A:Place about 1 g in a flask equipped with a stopper and glass tubing, the tip of which is immersed in calcium hydroxide TS in a test tube.
Add 5 mL of 3 N hydrochloric acid to the flask, and immediately insert the stopper: gas evolves in the flask and a precipitate is formed in the test tube.
B:The solution remaining in the flask responds to the tests for Aluminum (191).
MICROBIAL ENUMERATION TESTS (61), and TESTS FOR SPECIFIED MICROORGANISMS (62)-Its total aerobic microbial count does not exceed 100 cfu per mL, and it meets the requirements of the test for the absence of Escherichia coli.
ACID-NEUTRALIZING CAPACITY (301)-Not less than 65.0% of the expected mEq value, calculated from the results of the Assay, is obtained. Each mg of Al(OH)3, has an expected acid-neutralizing capacity value of 0.0385 mEq.
PH (791): between 5.5 and 8.0, determined potentiometrically.
Chloride-Transfer an accurately measured quantity of the Gel, equivalent to 0.6 g of Al(OH)3, to a porcelain dish. Add 0.1 mL of potassium chromate TS and 25 mL of water. Stir, and add 0.10 N silver nitrate until a faint, persistent pink color is obtained: not more than 8.0 mL of 0.10 N silver nitrate is required [4.7%, based on the Al(OH)3 content].
SULFATE (221)-Add 5.0 mL of 3 N hydrochloric acid to an accurately measured quantity of the Gel, equivalent to 0.3 g of Al(OH)3, and heat to dissolve the specimen under test. Cool, dilute with water to 250 mL, and filter if necessary: a 20-mL portion of the filtrate shows no more sulfate than corresponds to 0.20 mL of 0.020 N sulfuric acid [0.8%, based on the Al(OH)3, content].
Change to read:
ARSENIC (211), Procedures, Procedure 1 (CN 1-Jun-2023) -Prepare a Standard Preparation as directed in the test for Arsenic (211), Procedures.
Procedure 1 (CN 1-Jun-2023), except to prepare it to contain 5 µg of arsenic instead of 3 µg. Prepare the Test Preparation as follows. Dissolve an accurately measured quantity of the Gel, equivalent to 0.5 g of Al(OH)3, in 20 mL of 7 N sulfuric acid. The limit is 0.001%, based on the Al(OH)3 content.
Assay-
Edetate disodium titrant-Prepare and standardize as directed in the Assay under Ammonium Alum.
Procedure-Transfer an accurately measured quantity of Gel, equivalent to about 1.5 g of Al(OH)3, to a beaker, add 15 mL of hydrochloric acid, and heat gently until solution is complete. Cool, transfer to a 500-mL volumetric flask, dilute with water to volume, and mix. Pipet 20 mL of this solution into a 250-mL beaker, and add, in the order named and with continuous stirring, 25.0 mL of Edetate disodium titrant and 20 mL of acetic acid-ammonium acetate buffer TS, then heat the solution near the boiling point for 5 minutes. Cool, and add 50 mL of alcohol and 2 mL of dithizone TS. Titrate the solution with 0.05 M zinc sulfate VS until the color changes from green-violet to rose-pink. Perform a blank determination, substituting 20 mL of water for the sample, and make any necessary correction. Each mL of 0.05 M Edetate disodium titrant consumed is equivalent to 3.900 mg of Al(OH)3.
