In-beam electron ionization mass spectra of penicillins

Area of Science:

• Analytical Chemistry
• Organic Chemistry
• Mass Spectrometry

Background:

• Conventional direct-insertion probe mass spectrometry often fails to detect molecular ion peaks for penicillins.
• Understanding the mass spectral characteristics of penicillins is crucial for their identification and structural elucidation.

Purpose of the Study:

• To establish the characteristics of in-beam electron ionization mass spectra for 6-aminopenicillanic acid and various penicillins.
• To investigate methods for obtaining detectable molecular ion peaks for challenging penicillin compounds.

Main Methods:

• In-beam electron ionization mass spectrometry was employed for analyzing 6-aminopenicillanic acid and several penicillins.
• Mass analyzed ion kinetic energy spectrometry was used to study the fragmentation of penicillin G.
• A desorption technique using polyethylene glycol 4000 was utilized for ampicillin and amoxicillin analysis.

Main Results:

• In-beam electron ionization mass spectra revealed molecular ion or (M+1) peaks for most studied penicillins, unlike conventional methods.
• Spectral features were comparable to methyl ester or amide derivatives, aiding identification.
• Satisfactory spectra for ampicillin and amoxicillin were obtained using a polyethylene glycol 4000 desorption technique.

Conclusions:

• In-beam electron ionization mass spectrometry is effective for obtaining molecular ion information from penicillins that are difficult to analyze by conventional means.
• The fragmentation of penicillin G under electron impact was characterized.
• The developed desorption technique enhances the applicability of mass spectrometry for analyzing complex penicillin structures.