Determination of N-Methylpyrrolidine in Cefepime Using a Reagent-Free Ion Chromatography System

Significance of the topic

Cephalosporins are widely used for treating bacterial infections; cefepime, a fourth-generation cephalosporin, degrades at ambient temperatures to produce N-methylpyrrolidine (NMP), which is potentially toxic. Monitoring NMP levels is essential for ensuring drug purity and patient safety.

Objectives and study overview

Develop a rapid, sensitive, and simplified ion chromatography method for quantifying NMP in cefepime formulations using reagent-free methanesulfonic acid eluent and suppressed conductivity detection. Compare performance to current USP compendial methods and assess applicability to raw material and finished product samples.

Methodology and instrumentation

• Instrumentation: Dionex ICS-3000 RFIC-EG system with SP/DP pump, EGC II MSA cartridge, CR-CTC II trap column, CSRS 300 detector, autosampler, Chromeleon software
• Column: IonPac CG17 guard (2×50 mm) and CS17 analytical (2×250 mm)
• Eluent: Electrolytically generated MSA gradient (6 mM for 0–7.5 min, 85 mM for 7.5–20 min, 6 mM for 20–30 min)
• Flow rate: 0.4 mL/min; Column temp: 40–50 °C; Detector temp: 30 °C
• Detection: Suppressed conductivity, recycle mode, 100 mA
• Samples: Cefepime hydrochloride, simulated injection (with arginine), USP system suitability reference material

Main results and discussion

• NMP elutes at ~5.3 min; total run time is 35 min for cefepime hydrochloride, reducing analysis from USP’s 55 min to 35 min
• Linearity: r2=0.9999 across 0.45–200 µg/mL; LOQ 0.10 µg/mL (0.001%); LOD 0.03 µg/mL
• Precision: Peak area RSD <1.3%, retention time RSD <0.8% intra-day and <0.5% inter-day
• Accuracy: Spike recoveries between 97.8% and 102.0%
• Method extends to cefepime for injection (with 7.25 mg/mL arginine) and system suitability sample, achieving baseline separation (RS>1.3) and runtimes around 45 min
• Stability study: At 25 °C, NMP in cefepime increases from 0.23% to ~2% over 3 days; refrigerated and frozen storage maintain stability over 96 hours

Benefits and practical applications

• Faster throughput and lower solvent consumption compared to USP methods
• Reagent-free eluent generation simplifies preparation and avoids pH-induced degradation
• High sensitivity allows quantitation well below pharmacopeial limits
• Suitable for QC of raw materials, formulated products, and stability testing

Future trends and possibilities for application

The approach may be adapted to other β-lactam degradation products and combined with mass spectrometry for comprehensive impurity profiling. Miniaturized columns and automated platforms could further increase efficiency and reduce waste.

Conclusion

The developed RFIC method with IonPac CS17 and suppressed conductivity detection offers a rapid, accurate, and sensitive quantification of NMP in cefepime products, meeting and exceeding USP requirements while improving lab productivity.

Reference

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4. FDA. Maxipime (Cefepime Hydrochloride) for Injection. MedWatch 2003.
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7. Dionex Application Note 157: Comparison of Suppressed to Nonsuppressed Conductivity Detection. 2004.
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