Partially-Neutralized Methacrylic Acid and Ethyl Acrylate Copolymer
Click to View Image

Partially-neutralized poly(methacrylic acid, ethyl acrylate);    
Partially-neutralized methacrylic acid–ethyl acrylate copolymer     [25212-88-8].
DEFINITION
Partially-Neutralized Methacrylic Acid and Ethyl Acrylate Copolymer consists of methacrylic acid and ethyl acrylate monomers arranged in a random distribution, some units of methacrylic acid in the copolymer are neutralized by sodium hydroxide. The non-neutralized methacrylic acid units in the partially-neutralized methacrylic acid and ethyl acrylate copolymer are NLT 43.2% and NMT 47.6%, calculated on the dried basis. It may contain suitable emulsifiers.
IDENTIFICATION
•  A. Infrared Absorption
Sample:  100 mg of Partially-Neutralized Methacrylic Acid and Ethyl Acrylate Copolymer
Analysis:  Dissolve the Sample in 1 mL of dehydrated alcohol, and place 2 drops of the solution on a sodium chloride (or potassium bromide) plate. Dry to evaporate the solvent and allow to form a film and cover with another sodium chloride (or potassium bromide) plate.
Acceptance criteria:  The IR absorption spectrum of Partially-Neutralized Methacrylic Acid and Ethyl Acrylate Copolymer exhibits maxima corresponding to the same wavelengths as that of a similar preparation of USP Partially-Neutralized Methacrylic Acid and Ethyl Acrylate Copolymer (1:1) RS, treated in the same manner.
•  B. It meets the requirements of the Assay.
ASSAY
•  Procedure
Sample:  1 g, calculated on the dried basis
Analysis:  Dissolve the Sample in 40 mL of water and 60 mL of 2-propanol, and titrate with 0.1 N sodium hydroxide VS, determining the endpoint potentiometrically (see Titrimetry 541). Each mL of 0.1 N sodium hydroxide is equivalent to 8.609 mg of methacrylic acid (C4H6O2) units.
Acceptance criteria:  43.2%–47.6% for Partially-Neutralized Methacrylic Acid and Ethyl Acrylate Copolymer
IMPURITIES
Inorganic Impurities 
•  Residue on Ignition 281: 2.0%–3.5%
•  Heavy Metals, Method II 231: NMT 20 ppm
Organic Impurities 
•  Procedure: Limit of Methacrylic Acid and Ethyl Acrylate
Phosphoric acid solution:  0.1% phosphoric acid prepared from phosphoric acid
Mobile phase:  Methanol and Phosphoric acid solution (3:7)
Standard solution:  1.0 µg/mL each of methacrylic acid and ethyl acrylate in methanol
Sample solution:  Transfer 0.5 g of Partially-Neutralized Methacrylic Acid and Ethyl Acrylate Copolymer to a 25-mL volumetric flask, and dissolve in 20 mL of methanol. Add Phosphoric acid solution dropwise to precipitate the polymer while continuously stirring until the volume of 25 mL is reached. [Note—Stir with a magnetic stirrer for 10 min. Any volume deviation caused by the precipitation is negligible for contents in the ppm range. Use a magnetic stirrer of appropriate size to avoid a large variance from the final volume of the Sample solution. ] As soon as the solid matter has settled, pass the supernatant through a filter of 0.45-µm pore size. [Note—Solution that cannot be filtered is centrifuged at NLT 20,000 × g for NLT 30 min. ] Use the clear supernatant.
Chromatographic system 
Mode:  LC
Detector:  UV 205 nm
Column:  4.0-mm × 12.5-cm analytical column, 5-µm packing L1 or 4.6-mm × 15.0-cm analytical column, 5-µm packing L1
Flow rate:  1.2 mL/min
Injection size:  20 µL
[Note—Where appropriate, the volume must be adapted to the sensitivity of the detector. ]
[Note—Column switching system may be used for extension of column lifetime. ]
System suitability 
Sample:  Standard solution
[Note—The relative retention times for methacrylic acid and ethyl acrylate are 1.0 and 2.2, respectively. ]
Suitability requirements 
Resolution:  NLT 5.0 between methacrylic acid and ethyl acrylate
Relative standard deviation:  NMT 5.0%
Analysis 
Samples:  Standard solution and Sample solution
Calculate the percentage of each monomer (methacrylic acid or ethyl acrylate) in the portion of Methacrylic Acid and Ethyl Acrylate Copolymer taken:
Result = (rU/rS) × (CS/W) × VF × F × 100
rU== peak response from the Sample solution
rS== peak response from the Standard solution
CS== concentration of the Standard solution (µg/mL)
W== weight of Partially-Neutralized Methacrylic Acid and Ethyl Acrylate Copolymer taken to prepare the Sample solution (g)
VF== final volume of the Sample solution, 25 mL
F== conversion factor, 106 g/µg
Acceptance criteria:  NMT 0.01% for the total amount of monomers
SPECIFIC TESTS
•  Loss on Drying 731: Dry a sample at 110 for 6 h: it loses NMT 5.0% of its weight.
•  Viscosity 911: Weigh 400 g of water into a short form, 600-mL beaker (internal diameter about 80 mm and height 120 mm). After determining the Loss on Drying, weigh a quantity of undried Partially-Neutralized Methacrylic Acid and Ethyl Acrylate Copolymer, equivalent to 100 g on the dried basis. Transfer the sample to the beaker very slowly while effectively stirring (avoid lumps). Ensure that the stirring is very effective at the beginning and that the powder is immersed very slowly at the same time. Once the powder is dispersed and no lumps are visible, gentle stirring is then sufficient. Ensure a colloidal dispersion (milky white liquid) by stirring at room temperature for 3 h and taking care to avoid mixing in excess air. Afterwards allow the container to stand for 1 h, control the temperature to 23 ± 0.1, and let the entrapped air dissipate. [Note—Ensure that the concentration of this solution is 20% (w/w). ] Determine the viscosity of this solution at 23 ± 0.1 using a suitable rotational viscometer with a cylindrical spindle 1.9 cm in diameter and 6.5 cm high, attached to a shaft 0.3 cm in diameter.1 The spindle rotates at 50 rpm at an immersion depth of 8.1 cm. Follow the instrument manufacturer's directions to measure the apparent viscosity.
Acceptance criteria:  20–100 mPa·s
ADDITIONAL REQUIREMENTS
•  Packaging and Storage: Preserve in tight containers, and store at controlled room temperature.
•  Labeling: Label it to indicate the range of non-neutralized methacrylic acid units. The labeling also indicates the name and quantity of any emulsifier if the content is 0.10% or greater.
•  USP Reference Standards 11
USP Partially-Neutralized Methacrylic Acid and Ethyl Acrylate Copolymer (1:1) RS

1  A suitable spindle is available from Brookfield as an LV1 spindle, or the equivalent.
Auxiliary Information— Please check for your question in the FAQs before contacting USP.
Topic/Question Contact Expert Committee
Monograph Robert H. Lafaver, M.S.
Scientific Liaison
1-301-816-8335
(EXC2010) Monographs - Excipients
Reference Standards RS Technical Services
1-301-816-8129
rstech@usp.org
USP35–NF30 Page 1863
Pharmacopeial Forum: Volume No. 35(5) Page 1204