» Carbomer Interpolymer is a carbomer homopolymer or copolymer that contains a block copolymer of polyethylene glycol and a long chain alkyl acid ester.
NOTE—Different types of Carbomer Interpolymers may not have identical properties with respect to their use for specific pharmaceutical purposes, e.g., as tablet controlled-release agents, bioadhesives, topical gels, thickening agents, and emulsifying agents. Therefore, different types of Carbomer Interpolymers should not be interchanged unless performance equivalency has been ascertained.
Packaging and storage—
Preserve in tight containers, at a temperature not exceeding 45
.
Change to read:
Labeling—
Label it to indicate
whether it is Type A, B, or C; and also to state
NF24 the measured viscosity, the solvent or solvents used in the polymerization process, and the nominal and measured residual solvent levels for each solvent.
Identification—
A:
Infrared Absorption 
197K
—The IR absorption spectrum exhibits bands at or near (±5) wave numbers (cm
1) 1710, 1454, 1414, 1245, 1172, 1115, and 801, with the strongest band at 1710.
B:
Without mixing, add 2.5 g of Carbomer Interpolymer to 500 mL of water in an 800-mL beaker, and allow to stand. The powders wet out in not more than 60 minutes.
C:
Add about 5 g of Carbomer Interpolymer to 500 mL of water, stir, and adjust with 1 N sodium hydroxide to a pH of about 7.5. It forms a viscous gel.
Viscosity 911—
Carbomer Interpolymer A—
Proceed as directed for
Viscosity under
Carbomer Copolymer, except to perform the test on a 0.5% aqueous dispersion prepared by using 2.50 g instead of 5.00 g of copolymer.
Carbomer Interpolymer B—
Proceed as directed for
Viscosity under
Carbomer Copolymer, except to adjust the pH of the dispersion to within the range of 5.8 to 6.3 instead of 7.3 to 7.8.
Carbomer Interpolymer C—
Proceed as directed for
Viscosity under
Carbomer Copolymer, except to perform the test on a 0.5% aqueous dispersion prepared by using 2.50 g instead of 5.00 g of copolymer and to adjust the pH of the dispersion to within the range of 5.8 and 6.3 instead of 7.3 to 7.8. The viscosity values, determined by the conditions specified herein, are within the limits specified in the accompanying table.
| Carbomer Interpolymer |
Viscosity Specifications, in cP |
| A |
45,000–65,000 |
| B |
47,000–77,000 |
| C |
8,500–16,500 |
Loss on drying 731—
Dry it in vacuum at 80
for 1 hour: it loses not more than 2.0% of its weight.
Limit of ethyl acetate and cyclohexane—
[NOTE—This test is required only for those Carbomer Interpolymers where the labeling indicates that ethyl acetate or a mixture of ethyl acetate and cyclohexane was used in the polymerization process.
]
Standard stock solution—
Proceed as directed in the test for
Limit of ethyl acetate and cyclohexane under
Carbomer Copolymer, except to use 20 µL of ethyl acetate and 10 µL of cyclohexane.
Standard solution—
Proceed as directed in the test for
Limit of ethyl acetate and cyclohexane under
Carbomer Copolymer to obtain a solution containing 0.18 mg of ethyl acetate and 0.078 mg of cyclohexane.
Test solution and Chromatographic system—
Proceed as directed in the test for
Limit of ethyl acetate and cyclohexane under
Carbomer Copolymer.
Procedure—
Proceed as directed in the test for
Limit of ethyl acetate and cyclohexane under
Carbomer Copolymer, except to calculate the percentages of ethyl acetate and cyclohexane in the portion of Carbomer Interpolymer taken by the formula:
100(WS / WT)(RU / RS)
in which
WT is the weight, in mg, of Carbomer Interpolymer taken to prepare the
Test solution; and the other terms are as defined therein: not more than 0.35% of ethyl acetate and not more than 0.15% of cyclohexane is found.
Add the following:
Limit of benzene—
Solvent solution—
Quantitatively dissolve an accurately weighed quantity of benzene in dimethyl sulfoxide to obtain a solution having a concentration of about 1.0 mg per mL. Dilute this solution quantitatively, and stepwise if necessary, with organic-free water (see
Organic Volatile Impurities 467) to obtain a solution having a concentration of about 0.1 µg per mL.
Test solution—
Transfer about 50 mg of Carbomer Interpolymer, accurately weighed, to a 10-mL volumetric flask. Add about 7.5 mL of sodium chloride solution (2 in 100), and mix by mechanical means until homogeneous (usually about 30 minutes). Dilute with sodium chloride solution (2 in 100) to volume, and mix until homogeneous (usually less than 1 minute). [NOTE—This preparation must be analyzed within 3 hours of preparation.]
Reference solution—
Transfer about 50 mg of Carbomer Interpolymer, accurately weighed, to a 10-mL volumetric flask. Add about 7.5 mL of sodium chloride solution (2 in 100), and mix by mechanical means until homogeneous (usually about 30 minutes). Add 1.0 mL of the Solvent solution, dilute with sodium chloride solution (2 in 100) to volume, and mix until homogeneous (usually less than 1 minute). This solution contains about 0.01 µg of benzene per mL.
Chromatographic system—
Proceed as directed in the test for
Limit of benzene under
Carbomer Copolymer.
Procedure—
Proceed as directed in the test for
Limit of benzene under
Carbomer Copolymer. Calculate the percentage of benzene in the portion of Carbomer Interpolymer taken by the formula:
(C/W)(rU / rS)
in which
C is the concentration, in µg per mL, of benzene in the
Reference solution; W is the weight, in mg, of Carbomer Interpolymer taken to prepare the
Test solution; and
rU and
rS are the benzene peak responses obtained from the
Test solution and the
Reference solution, respectively: not more than 0.0002% is found.
NF24
Limit of acrylic acid—
pH 3.0 Phosphate buffer, Mobile phase, Standard solution, Test solution, and Chromatographic system—
Proceed as directed in the test for
Limit of acrylic acid under
Carbomer Copolymer.
Procedure—
Proceed as directed in the test for
Limit of acrylic acid under
Carbomer Copolymer, except to calculate the percentage of free acrylic acid in the portion of Carbomer Interpolymer taken by the formula:
(C/W)(rU / rS)
in which
W is the weight, in mg, of Carbomer Interpolymer taken to prepare the
Test solution; and the other terms are as defined therein: not more than 0.25% is found.
Content of carboxylic acid—
Proceed as directed in the test for
Content of carboxylic acid under
Carbomer Copolymer, except to calculate the percentage of carboxylic acid in the portion of Carbomer Interpolymer taken by the formula:
100(45.02VN/W)
in which
W is the weight, in mg, of the portion of Carbomer Interpolymer taken; and the other terms are as defined therein. The carboxylic acid content is not less than 52.0% and not more than 62.0%.
