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Methacrylic Acid Copolymer
» Methacrylic Acid Copolymer is a fully polymerized copolymer of methacrylic acid and an acrylic or methacrylic ester. Type C may contain suitable surface-active agents. The assay and viscosity requirements differ for the several types, as set forth in the accompanying table.
Methacrylic acid
units, dried basis (%)		 Viscosity (cps)
Type Min. Max. Min. Max.
A 46.0 50.6 50 200
B 27.6 30.7 50 200
C 46.0 50.6 100 200
Packaging and storage— Preserve in tight containers.
Labeling— Label it to state whether it is Type A, B, or C.
Identification—
B: Pour a few mL of the solution prepared for the Viscosity test onto a glass plate, and allow the solvent to evaporate: a clear, brittle film results.
Viscosity 911— Place 254.6 g of isopropyl alcohol and 7.9 g of water in a conical flask having a ground-glass joint. Add a quantity of Methacrylic Acid Copolymer, accurately weighed and equivalent to 37.5 g of solids on the dried basis, while stirring by means of a magnetic stirrer. Close the flask, and continue stirring until the polymer has dissolved completely. Adjust the temperature to 20 ± 0.1. Equip a suitable rotational viscosimeter with a spindle having a cylinder 1.88 cm in diameter and 6.25 cm high attached to a shaft 0.32 cm in diameter, the distance from the top of the cylinder to the lower tip of the shaft being 0.75 cm, and the immersion depth being 8.15 cm (No. 1 spindle). With the spindle rotating at 30 rpm, immediately observe and record the scale reading. Convert the scale reading to centipoises by multiplying the reading by the constant for the viscosimeter spindle and speed employed.
Loss on drying 731— Dry it at 110 for 6 hours: it loses not more than 5.0% of its weight.
Residue on ignition 281: not more than 0.1% for Types A and B; not more than 0.4% for Type C.
Change to read:
Limit of monomers—
pH 2.0 Phosphate buffer, 0.025 MNF24 —Prepare an aqueous solution containing 3.550 g of anhydrousNF24 dibasic sodium phosphate (Na2HPO4) and 3.400 g of monobasic potassium phosphate (KH2PO4) per L. Adjust with phosphoric acid to a pH of 2.0.
Mobile phase— Prepare a solution in methanol to contain 700 mL of pH 2.0 Phosphate buffer, 0.025 MNF24 per L.
Standard solution— Prepare a solution in methanol to contain an accurately known concentration of about 2.4 µg per mL each of methacrylic acid and either methyl methacrylate (for Type A and Type B) or ethyl acrylate (for Type C). To 50.0 mL of this solution, add 25.0 mL of water, and mix.
Test solution— Dissolve about 40 mg of Methacrylic Acid Copolymer, accurately weighed, in 50.0 mL of methanol, add 25.0 mL of water, and mix.
Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a 202-nm detector and a 4-mm × 12.5-cm column that contains 5-µm packing L1. The flow rate is about 2.5 mL per minute. Chromatograph the Standard solution, and record the peak responses as directed for Procedure: the resolution, R, of each pair of analytes is not less than 2.0; the capacity factors, k¢, for methacrylic acid, ethyl acrylate, and methyl methacrylate are 1.7, 4.3, and 4.8, respectively; and the relative standard deviation for replicate injections determined from each analyte is not more than 2%.
Procedure— Separately inject equal volumes (about 50 µL) of the Standard solution and the Test solution into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the quantity, in µg, of each monomer in the portion of Methacrylic Acid Copolymer taken by the formula:
75C(rU / rS)
in which C is the concentration, in µg per mL, of the monomer in the Standard solution; and rU and rS are the peak responses for the monomer obtained from the Test solution and the Standard solution, respectively. Not more than 0.05% of total monomers is found.
Organic volatile impurities, Method V 467: meets the requirements.
Solvent— Use dimethyl sulfoxide.
Residual solvents 467: meets the requirements.
(Official January 1, 2007)
Assay— Dissolve about 1 g of Methacrylic Acid Copolymer, previously dried and accurately weighed, in 100 mL of neutralized acetone, add 1 drop of phenolphthalein TS, and titrate with 0.1 N sodium hydroxide VS until a pink color persists for 15 seconds. Each mL of 0.1 N sodium hydroxide is equivalent to 8.609 mg of methacrylic acid (C4H6O2) units.
Auxiliary Information— Staff Liaison : Hong Wang, Ph.D. , Senior Scientific Associate
Expert Committee : (EM205) Excipient Monographs 2
USP29–NF24 Page 3371
Pharmacopeial Forum : Volume No. 31(1) Page 93
Phone Number : 1-301-816-8351