Mass Spectrometry

Definition

Mass spectrometry (MS) is an analytical technique that measures the mass-to-charge ratio (m/z) of ionized molecules in the gas phase. For peptide analysis, electrospray ionization (ESI-MS) and matrix-assisted laser desorption ionization (MALDI-TOF-MS) are the primary ionization methods. ESI-MS produces multiply charged ions from peptides in solution, and the resulting m/z spectrum allows calculation of the molecular weight. MALDI-TOF produces primarily singly charged ions and is particularly useful for larger peptides and proteins. Mass spectrometry provides molecular weight data with high accuracy (typically within 1 Da for ESI-MS of research peptides), enabling definitive identity confirmation.

Research Context

Mass spectrometry is the gold standard for confirming the identity of research-grade peptide compounds. While HPLC establishes purity, mass spectrometry confirms that the main peak corresponds to the intended peptide by verifying its molecular weight matches the theoretical value calculated from the amino acid sequence. MS data on the certificate of analysis of research-grade peptides provides independent identity confirmation beyond purity. Advanced MS techniques including tandem MS (MS/MS) can additionally verify the amino acid sequence of a peptide through fragmentation pattern analysis.