Aluminum Zirconium Octachlorohydrate
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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)
AlyZr(OH)3y+4-xClx·nH2O
>> Aluminum Zirconium Octachlorohydrate is a polymeric, loosely hydrated complex of basic aluminum zirconium chloride that encompasses a range of aluminum-to-zirconium atomic ratios between 6.0:1 and 10.0:1, and a range of (aluminum plus zirconium)-to-chloride atomic ratios between 1.5:1 and 0.9:1. It contains not less than 90.0 percent and not more than 110.0 percent of the labeled amount of anhydrous aluminum zirconium octachlorohydrate.
1 Packaging and storage
Preserve in well-closed containers.
2 Labeling
The label states the content of anhydrous aluminum zirconium octachlorohydrate.
3 Identification
A solution (1 in 10) responds to the test for Chloride (191).
4 PH (791)
Between 3.0 and 5.0, in a solution [15 in 100 (w/w)].
Change to read:
5 ARSENIC (211), Procedures, Procedure 1 (CN 1-Jun-2023)
2 µg per g.
Change to read:
6 Limit of iron
6.1 Standard preparation
Transfer 2.0 mL of Standard Iron Solution, prepared as directed under Iron (241), Procedures, Procedure 1 (CN 1-Jun-2023), to a 50-mL beaker.
6.2 Test preparation
Transfer 2.7 g of Aluminum Zirconium Octachlorohydrate to a 100-mL volumetric flask, dilute with water to volume, and mix. Transfer 5.0 mL of this solution to a 50-mL beaker.
6.3 Procedure
To each of the beakers containing the Standard preparation and the Test preparation add 5 mL of 6 N nitric acid, cover with a watch glass, and boil on a hot plate for 3 to 5 minutes. Allow to cool, add 5 mL of Ammonium Thiocyanate Solution, prepared as directed under Iron (241), transfer to separate 50-mL color comparison tubes, dilute with water to volume, and mix: the color of the solution from the Test preparation is not darker than that of the solution from the Standard preparation (150 µg per g).
7 Content of aluminum
Transfer about 0.15 g of Aluminum Zirconium Octachlorohydrate, accurately weighed, to a 150-mL beaker, and add 5 mL of water and 15 mL of hydrochloric acid. Heat this solution to boiling, and continue boiling for 5 minutes. Add 40 mL of water and 15.0 mL of 0.1 M edetate disodium VS. Heat the solution to boiling, and continue boiling for 5 minutes. Allow the solution to cool, add 10 to 15 mL of acetic acid-ammonium acetate buffer TS, and adjust with ammonium hydroxide to a pH of 4.5 ± 0.1. Add 20 mL of alcohol, and adjust with ammonium hydroxide to a pH of 4.6 ± 0.1. Add 5 to 10 drops of dithizone TS, and titrate with 0.1 M zinc sulfate VS until the first permanent purple-pink color appears. Perform a blank determination, and make any necessary correction. Calculate the percentage of aluminum (Al) in the Aluminum Zirconium Octachlorohydrate by the formula:
2.698[15.0Me-(zMz + Ze)]/W
in which Me is the molarity of the edetate disodium VS; z is the volume, in mL, of zinc sulfate VS consumed; Mz is the molarity of the zinc sulfate VS; W is the quantity, in g, of Aluminum Zirconium Octachlorohydrate taken; Ze is the equivalent volume, in mL, of edetate disodium VS consumed by the zirconium moiety, calculated as follows:
(Zr/Me)(W/92.97)
in which Zr is the percentage of zirconium as determined in the test for Content of zirconium, 92.97 is the atomic weight of zirconium corrected for 2% hafnium content, and the other terms are as defined above. Use the result obtained to calculate the Aluminum/zirconium atomic ratio and the (Aluminum plus zirconium)/chloride atomic ratio.
8 Content of zirconium
Transfer about 250 mg of Aluminum Zirconium Octachlorohydrate, accurately weighed, to a 150-mL beaker, and add 5 mL of water and 15 mL of hydrochloric acid. Heat this solution to boiling, and continue boiling for 6 to 8 minutes. Add 30 to 40 mL of water and 5 mL of hydrochloric acid, and heat to boiling. Add 1 drop of xylenol orange TS, and, while still hot, titrate with 0.1 M edetate disodium VS until the color of the solution changes from pink to yellow. Perform a blank determination, and make any necessary correction. Each mL of 0.1 M edetate disodium is equivalent to 9.297 mg of zirconium (Zr). Use the result obtained to calculate the Aluminum/zirconium atomic ratio and the (Aluminum plus zirconium)/chloride atomic ratio.
9 Aluminum/zirconium atomic ratio
Divide the percentage of aluminum found in the test for Content of aluminum by the percentage of zirconium found in the test for Content of zirconium, and multiply by 92.97/26.98, in which 92.97 is the atomic weight of zirconium corrected for 2% hafnium content, and 26.98 is the atomic weight of aluminum: the ratio is between 6.0:1 and 10.0:1.
10 Content of chloride
Transfer about 250 mg of Aluminum Zirconium Octachlorohydrate, accurately weighed, to a 250-mL beaker, add 100 to 120 mL of water and 20 mL of diluted nitric acid, and swirl to dissolve. Titrate with 0.05 N silver nitrate VS using a calomel electrode and a silver billet electrode system, determining the endpoint potentiometrically. Each mL of 0.05 N silver nitrate is equivalent to 1.773 mg of chloride (CI). Use the result obtained to calculate the (Aluminum plus zirconium)/chloride atomic ratio.
11 (Aluminum plus zirconium)/chloride atomic ratio
Calculate the (aluminum plus zirconium)/chloride atomic ratio by the formula:
[(Al/26.98) + (Zr/92.97)]/(Cl/35.453)
in which Al, Zr, and C/ are the percentages of aluminum, zirconium, and chloride as determined in the tests for Content of aluminum, Content of zirconium, and Content of chloride, respectively; 26.98 is the atomic weight of aluminum; 92.97 is the atomic weight of zirconium corrected for 2% hafnium content; and 35.453 is the atomic weight of chlorine: the ratio is between 1.5:1 and 0.9:1.
12 Assay
Calculate the percentage of anhydrous aluminum zirconium octachlorohydrate in the Aluminum Zirconium Octachlorohydrate by the formula:
Al({26.98y + 92.97 + 17.01[3y + 4 - (y+1)/z] + 35.453(y + 1)/z}/26.98y)
in which Al is the percentage of aluminum found in the test for Content of aluminum, y is the aluminum/zirconium atomic ratio found in the test for Aluminum/zirconium atomic ratio, z is the (aluminum plus zirconium)/chloride atomic ratio found in the test for (Aluminum plus zirconium)/chloride atomic ratio, 26.98 is the atomic weight of aluminum, 92.97 is the atomic weight of zirconium corrected for 2% hafnium content, 17.01 is the molecular weight of the hydroxide anion (OH), and 35.453 is the atomic weight of chlorine (CI).
