Caffeine is anhydrous or contains one molecule of water of hydration. It contains NLT 98.5% and NMT 101.0% of C8H10N4O2, calculated on the anhydrous basis.
• B. The retention time of the caffeine peak of the Sample solution corresponds to that of the Standard solution, as obtained in the Assay.
Buffer: 0.82 g/L of anhydrous sodium acetate
Mobile phase: Acetonitrile, tetrahydrofuran, and Buffer (25:20:955). Adjust with glacial acetic acid to a pH of 4.5.
System suitability solution: 0.02 mg/mL of theophylline in Mobile phase. Shake, and sonicate if necessary, to dissolve.
Standard solution: Transfer 5.0 mg of USP Caffeine RS to a 25-mL volumetric flask. Add 5.0 mL of the System suitability solution and 10 mL of Mobile phase. Shake, and sonicate if necessary. Dilute with Mobile phase to volume, and filter.
Sample solution: 0.2 mg/mL of Caffeine in Mobile phase. [NoteShake, and sonicate if necessary, to dissolve. ]
Detector: UV 275 nm
Column: 4.6-mm × 15-cm; packing L1
Flow rate: 1 mL/min
Injection size: 10 µL
Sample: Standard solution
[NoteThe relative retention times for theophylline and caffeine are 0.69 and 1.0, respectively. ]
Resolution: NLT 6.0 between theophylline and caffeine
Tailing factor: NMT 2.0 for theophylline and caffeine peaks
Relative standard deviation: NMT 2.0%
Samples: Standard solution and Sample solution
Calculate the percentage of caffeine (C8H10N4O2) in the portion of Caffeine taken:
Result = (rU/rS) × (CS/CU) × 100
Acceptance criteria: 98.5%101.0% on the anhydrous basis
• Residue on Ignition 281: NMT 0.1%
• Heavy Metals, Method II 231: NMT 10 ppm
• Organic Impurities
Mobile phase, Standard solution, Sample solution, Chromatographic system, and System suitability: Proceed as directed in the Assay.
Sample: Sample solution
Calculate the percentage of each impurity in the portion of Caffeine taken:
Result = (rU/rT) × 100
Individual impurities: NMT 0.1%
Total impurities: NMT 0.1%
• Water Determination, Method III 921: Dry a sample at 80 for 4 h: the anhydrous form loses NMT 0.5% of its weight, and the hydrous form loses NMT 8.5% of its weight.
• Packaging and Storage: Preserve hydrous Caffeine in tight containers. Preserve anhydrous Caffeine in well-closed containers.
• Labeling: Label it to indicate whether it is anhydrous or hydrous.
• USP Reference Standards 11
Auxiliary Information Please check for your question in the FAQs before contacting USP.
USP35NF30 Page 2427Pharmacopeial Forum: Volume No. 34(5) Page 1150