Mass Spectrometry Analysis — Process Description

1. Principle

Electrospray ionization mass spectrometry (ESI-MS) produces gas-phase ions from peptide molecules in solution. Peptides with molecular weights of 500 – 5000 Da typically produce multiply charged ions, enabling accurate mass determination.

2. ESI-MS Interpretation

Charge State	m/z Value	Neutral Mass
[M+H]⁺	(M+1)/1	M = (m/z − 1) × 1
[M+2H]²⁺	(M+2)/2	M = (m/z × 2) − 2
[M+3H]³⁺	(M+3)/3	M = (m/z × 3) − 3

3. Acceptance Criteria

Parameter	Criteria
Mass Accuracy	Within ±0.5 Da of theoretical monoisotopic mass
Charge State Series	≥3 identifiable charge states for MW up to 5000 Da
Signal to Noise	≥10:1 for the base peak

4. Common Adducts

Adduct	Mass Shift (Da)
Na⁺	+22.0
K⁺	+38.0
TFA adduct	+113.0
Acetonitrile adduct	+41.0