Rapid determination of N-Methylpyrrolidine in Cefepime by combining direct infusion electrospray ionisation-time-of-flight mass spectrometry with field asymmetric waveform ion mobility spectrometry

The determination of N-methyl pyrrolidine, a potential impurity in the cephalosporin antibiotic cefepime, by direct infusion ESI combined with field asymmetric waveform ion mobility spectrometry-mass spectrometry (ESI-FAIMS-MS) is demonstrated. The addition of a chip-based FAIMS separation prior to detection by time-of-flight mass spectrometry enables selective transmission of NMP in the presence of cefepime without interference from NMP formed by CID in the mass spectrometer interface. The limits of detection and quantification of NMP in cefepime were 0.011% (w/w) and 0.036% (w/w) NMP in cefepime respectively, well below the 0.3% (w/w) threshold concentration for NMP in cefepime. The % relative standard deviation was 3.9% with linearity for standard additions in the range 0.005 – 0.5 μg/ml NMP. Novel Aspect (ToC) FAIMS separation prior to mass spectrometry enables selective transmission of NMP in cefepime without interference from NMP formed by in-source CID.