Ammonio Methacrylate Copolymer Dispersion

This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition

Issued and maintained by the United States Pharmacopeial Convention (USP)

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1 DEFINITION 

Ammonio Methacrylate Copolymer Dispersion is an aqueous dispersion of Ammonio Methacrylate Copolymer Type A or B in water. It may contain suitable antimicrobial preservatives and alkalizing agents. The Assay requirements differ for the two types, as set forth in the accompanying table. 

2 IDENTIFICATION

Change to read: 

A. Spectroscopic Identification Tests 〈197〉, Infrared Spectroscopy: 197K (CN 1-May-2020) 

Sample: Residue obtained in the test for Loss on Drying 

Acceptance criteria: Meets the requirements 

3 ASSAY 

Procedure 

Sample: Dry under vacuum 2 g of Ammonio Methacrylate Copolymer Dispersion Type A, or 4 g of Ammonio Methacrylate Copolymer Dispersion Type B, at 90° for 30 min. 

Blank: 75 mL of glacial acetic acid 

Titrimetric system 

(See Titrimetry 〈541〉.) 

Mode: Direct titration 

Titrant: 0.1 N perchloric acid VS 

Endpoint detection: Potentiometric 

Analysis: Dissolve the Sample in 75 mL of glacial acetic acid at about 50°, within about 30 min. After the solution has cooled down, add 25 mL of 0.6% cupric acetate solution in glacial acetic acid. Titrate this solution with the Titrant. Perform a blank determination. Calculate the percentage of ammonio methacrylate (C₉H₁₈ClNO₂) units in the portion of the Sample taken: 

Result ={[(V_s− V_B) × N × F]/W} × 100 

V_s= Titrant volume consumed by the Sample (mL)

V_B = Titrant volume consumed by the Blank (mL) 

N = actual normality of the Titrant (mEq/mL) 

F = equivalency factor, 207.72 mg/mEq 

W = Sample weight (mg) 

Acceptance criteria 

Type A: 10.18%–13.73% 

Type B: 6.11%–8.26% 

4 IMPURITIES 

Residue on Ignition 〈281〉 

Analysis: Using mild heating conditions (e.g., steam bath, sand bath, etc.) to avoid loss of material, evaporate the dispersion to dryness before ignition. 

Acceptance criteria: NMT 0.5% calculated on the undried dispersion basis 

Limit of Monomers 

Sodium perchlorate solution: 35 mg/mL of sodium perchlorate (NaClO₄ .H₂O) 

Mobile phase: Dilute phosphoric acid with water to obtain a solution having a pH of 2.0. Mix four volumes of this solution with one volume of methanol, lter, and degas. 

Standard stock solution: 1.6 mg/mL of ethyl acrylate and 0.2 mg/mL of methyl methacrylate in methanol 

Standard solution: Dilute 1 mL of the Standard stock solution with methanol to 100 mL. Add 10 mL of this solution to 5 mL of Sodium perchlorate solution. 

Sample solution: Dissolve 5 g of Dispersion in methanol, and dilute with the same solvent to 50 mL. Add 5 mL of Sodium perchlorate solution dropwise to 10 mL of this solution while continuously stirring. Remove the precipitated polymer by centrifugation. Use the clear supernatant. Calculate the concentration of Dispersion, in mg/mL, as C_U 

Chromatographic system 

(See Chromatography 〈621〉, System Suitability.) 

Mode: LC 

Detector: UV 202 nm 

Column: 4.6-mm × 12-cm; packing L1 

Flow rate: 2 mL/min 

Injection volume: 50 µL 

System suitability 

Sample: Standard solution 

[Note—The relative retention times for ethyl acrylate and methyl methacrylate are 1.00 and 1.14, respectively.] 

Suitability requirements 

Resolution: NLT 1.0 between the pair of analytes 

Relative standard deviation: NMT 5.0% 

Analysis 

Samples: Standard solution and Sample solution 

Calculate the percentage of ethyl acrylate and methyl methacrylate in the portion of Dispersion taken: 

Result = (r_U/r_S) × (C_S/C_U) × F × 100 

r_U = peak response of ethyl acrylate (or methyl methacrylate) from the Sample solution 

r_S = peak response of ethyl acrylate (or methyl methacrylate) from the Standard solution

C_S = concentration of ethyl acrylate (or methyl methacrylate) in the Standard solution (µg/mL) 

C_U = concentration of Ammonio Methacrylate Copolymer in the Sample solution (mg/mL) 

F = conversion factor, 10^-3 mg/µg 

Acceptance criteria: NMT 0.002% of methyl methacrylate and NMT 0.008% of ethyl acrylate 

5 SPECIFIC TESTS 

Viscosity—Rotational Methods 〈912〉 

Analysis: Use a viscometer equipped with a spindle having a cylinder 1.88 cm in diameter and 6.51 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 is 0.75 cm, and the immersion depth is 8.15 cm. Adjust the temperature to 20 ± 0.10°. With the spindle rotating at 30 rpm, immediately record the scale reading. Multiply the scale reading by the constant for the viscometer spindle and speed used to obtain the viscosity in centipoises. 

Acceptance criteria: NMT 100 mPa · s 

Loss on Drying 〈731〉 

Analysis: Dry a sample at 110° for 6 h. 

Acceptance criteria: 68.5%–71.5% 

Coagulum Content 

Sample: 100 g 

Analysis: Weigh a stainless steel sieve having 125-µm openings, and lter the Sample through it. Wash the sieve with distilled water until a clear ltrate is obtained, and dry the sieve to constant weight at 105°. 

Acceptance criteria: The weight of the residue does not exceed 1000 mg, corresponding to NMT 1%. 

6 ADDITIONAL REQUIREMENTS 

Packaging and Storage: Preserve in tight containers, at a temperature not exceeding 25° for Type A and not exceeding 30° for Type B. Protect from freezing. 

Labeling: Label it to state whether it is Type A or Type B. Label it to indicate the name and quantity of any added antimicrobial preservative or alkalizing agent. 

USP Reference Standards 〈11〉 

USP Ammonio Methacrylate Copolymer, Type A RS 

USP Ammonio Methacrylate Copolymer, Type B RS