Academy · Advanced
Mass Spectrometry Explained
ESI-MS and MALDI-TOF for peptide identity confirmation: ionisation, m/z, charge states and how to interpret the spectrum on your COA.
Ionisation modes
ESI (electrospray) is the workhorse for soluble peptides — gentle, multi-charged ions. MALDI-TOF is preferred for higher-mass or aggregation-prone peptides and produces mostly singly charged ions.
Charge states
ESI peptides typically appear as [M+H]+, [M+2H]2+, [M+3H]3+. Reconstructing the neutral mass from a charge envelope gives the most accurate molecular weight.
Reading the spectrum on a COA
Identify the principal m/z, deconvolve to the neutral mass, and compare against the theoretical mass for your sequence. Tolerance: ±0.1 Da on a low-resolution instrument, ±0.005 Da on high-res.
Frequently asked questions
Is mass spec required, or is HPLC enough?+
Mass spec is required to confirm identity. HPLC alone only tells you something is pure.
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