The choice of ionization method depends on the properties of the sample

MALDI

• Small molecules
• Peptides
• Proteins
• Polymers
• Organonometallics/polyconjugated aromatics

ESI

• LC-MS/MS: tandem mass spectrometry for peptide sequence/protein identification

EI

• GC-MS: gas chromatography/mass spectrometry
• EI-DIP: Direct Insertion Probe sampling