Methacrylic Acid Copolymer
»Methacrylic Acid Copolymer is a fully polymerized copolymer of methacrylic acid and an acrylic or methacrylic ester.Type Cmay 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—
A: Infrared Absorption á197Kñ.
B: Pour a few mLof the solution prepared for the Viscositytest onto a glass plate,and allow the solvent to evaporate:a clear,brittle film results.
Viscosity á911ñ— Place 254.6g of isopropyl alcohol and 7.9g of water in a conical flask having a ground-glass joint.Add a quantity of Methacrylic Acid Copolymer,accurately weighed and equivalent to 37.5g 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 1.88cm in diameter and 6.25cm high attached to a shaft 0.32cm in diameter,the distance from the top of the cylinder to the lower tip of the shaft being 0.75cm,and the immersion depth being 8.15cm (No.1spindle).With the spindle rotating at 30rpm,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 á731ñ— Dry it at 110for 6hours:it loses not more than 5.0%of its weight.
Residue on ignition á281ñ: not more than 0.1%for Types Aand B;not more than 0.4%for Type C.
Limit of monomers—
pH2.0Phosphate buffer,fortieth-molar— Prepare an aqueous solution containing 3.550g of dibasic sodium phosphate (Na2HPO4)and 3.400g of monobasic potassium phosphate (KH2PO4)per liter.Adjust with phosphoric acid to a pHof 2.0.
Mobile phase— Prepare a solution in methanol to contain 700mLof pH2.0Phosphate buffer,fortieth-molarper liter.
Standard solution— Prepare a solution in methanol to contain an accurately known concentration of about 2.4µg per mLeach of methacrylic acid and either methyl methacrylate (for Type Aand Type B)or ethyl acrylate (for Type C).To 50.0mLof this solution,add 25.0mLof water,and mix.
Test solution— Dissolve about 40mg of Methacrylic Acid Copolymer,accurately weighed,in 50.0mLof methanol,add 25.0mLof water,and mix.
Chromatographic system (see Chromatography á621ñ)— 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 2.5mLper 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 50µL)of the Standard solutionand the Test solutioninto 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 Cis the concentration,in µg per mL,of the monomer in the Standard solution;and rUand rSare the peak responses for the monomer obtained from the Test solutionand the Standard solution,respectively.Not more than 0.05%of total monomers is found.
Organic volatile impurities,Method Vá467ñ: meets the requirements.
Solvent— Use dimethyl sulfoxide.
Assay— Dissolve about 1g of Methacrylic Acid Copolymer,previously dried and accurately weighed,in 100mLof neutralized acetone,add 1drop of phenolphthalein TS,and titrate with 0.1Nsodium hydroxide VSuntil a pink color persists for 15seconds.Each mLof 0.1Nsodium hydroxide is equivalent to 8.609mg of methacrylic acid (C4H6O2)units.
Auxiliary Information— Staff Liaison:Catherine Sheehan,B.Sc.,Scientist
Expert Committee:(EMC)Excipients:Monograph Content
USP28–NF23Page 3035
Pharmacopeial Forum:Volume No.27(4)Page 2800
Phone Number:1-301-816-8262