• Heavy Metals 231: NMT 10 ppm
Standard solution: To 1 mL of USP Methylpyrrolidone RS, add 1 mL of pyrrolidone, and dilute with methylene chloride to 20 mL.
Sample solution: Methylpyrrolidone (neat)
Detector: Flame ionization
Column: 0.32-mm × 30-m fused-silica capillary column, 5-µm layer of phase G2
Column: See the temperature program table below.
Carrier gas: Nitrogen
Linear velocity: 20 cm/s
Split ratio: 100:1
Injection size: 1 µL
Sample: Standard solution
Resolution: NLT 2.0 between pyrrolidone and methylpyrrolidone
Samples: Standard solution and Sample solution
Calculate the percentage of each impurity, excluding any solvent peaks and peaks NMT 0.02%, in the portion of Methylpyrrolidone taken:
Result = (rU/rT) × 100
Acceptance criteria: NMT 0.1% of any individual impurity; and NMT 0.3% of total impurities
Bromothymol blue solution: Dissolve 50 mg of bromothymol blue in a mixture of 4 mL of 0.02 M sodium hydroxide and 20 mL of alcohol, and dilute with water to 100 mL.
Sample: Methylpyrrolidone (neat)
Analysis: Add 0.5 mL of Bromothymol blue solution as indicator to 50 mL of water, and adjust with 0.02 M potassium hydroxide or 0.02 M hydrochloric acid until a yellow color is obtained. Add 50 mL of the Sample. Titrate with 0.02 M hydrochloric acid to the initial coloration.
Acceptance criteria: NMT 8.0 mL of 0.02 M hydrochloric acid is required.
• Clarity of Solution
[NoteThe Sample is to be compared to the Reference suspension in diffused daylight 5 min after preparation of the Reference suspension. ]
Hydrazine solution: 10 mg/mL of hydrazine sulfate. [NoteAllow to stand 46 h before use. ]
Methenamine solution: Transfer 2.5 g of methenamine to a 100-mL glass-stoppered flask, add 25.0 mL of water, insert the glass stopper, and mix to dissolve.
Primary opalescent suspension
[NoteThis suspension is stable for 2 months, provided it is stored in a glass container free from surface defects. The suspension must not adhere to the glass and must be well mixed before use. ]
Transfer 25.0 mL of the Hydrazine solution to the Methenamine solution in the 100-mL glass-stoppered flask.
[NoteAllow to stand for 24 h. ]
Opalescence standard: Transfer 15.0 mL of the Primary opalescent suspension to a 1000-mL volumetric flask, and dilute with water to volume. [NoteThis suspension should not be used beyond 24 h after preparation. ]
Reference suspension: Transfer 5.0 mL of the Opalescence standard to a 100-mL volumetric flask, and dilute with water to volume.
Sample: Methylpyrrolidone (neat)
Analysis: Transfer a sufficient portion of the Sample to a test tube of colorless, transparent, neutral glass with a flat base and an internal diameter of 1525 mm to obtain a depth of 40 mm. Similarly transfer portions of the Reference suspension and water to separate matching test tubes. Compare the Sample, Reference suspension, and water in diffused daylight, viewing vertically against a black background (see Spectrophotometry and Light-Scattering 851, Visual Comparison). [NoteThe diffusion of light must be such that the Reference suspension can readily be distinguished from water. ]
Acceptance criteria: The Sample shows the same clarity as that of water, or its opalescence is not more pronounced than that of the Reference suspension.
• Color of Solution
Sample Methylpyrrolidone (neat)
Analysis: Transfer a sufficient portion of the Sample to a test tube of colorless, transparent, neutral glass with a flat base and an internal diameter of 1525 mm, to obtain a depth of 40 mm. Similarly transfer a portion of water to a separate matching test tube. Compare the color of the Sample with that of water in diffused daylight, viewing vertically against a white background (see Spectrophotometry and Light-Scattering 851, Visual Comparison).
Acceptance criteria: The Sample has the color of water.
• Water, Method Ic 921: NMT 0.1%, determined on 1.0 g
• Packaging and Storage: Preserve in light-resistant containers.
• USP Reference Standards 11
USP Methylpyrrolidone RS
Auxiliary Information Please check for your question in the FAQs before contacting USP.
USP35NF30 Page 1869Pharmacopeial Forum: Volume No. 35(5) Page 1205