Mass spectrometry (MS)

Mass spectrometry is used alongside HPLC to confirm that the purified peak in a research peptide really is the intended molecule. The peptide is ionised (commonly by electrospray, ESI) and the resulting ions are sorted by their mass-to-charge ratio. The observed mass is compared to the theoretical molecular weight calculated from the amino acid sequence — a match within ±1 Da on a low-resolution instrument, or sub-ppm on high-resolution, confirms identity. A complete batch test combines HPLC for purity with MS for identity.