Research concepts
Adducts and Charge States in Mass Spectrometry
Adducts and charge states in MS: Am I reading m/z or an already interpreted molecular mass?
Source editorial review:
Before interpreting the result
Am I reading m/z or an already interpreted molecular mass?
- Identify charge state and adduct assignment.
- Distinguish observed signal, deconvolution and theoretical reference mass.
- Look for consistency among related signals before assigning multiple molecules.
Adducts and charge states in MS
A mass spectrometer records ions by mass-to-charge ratio. One species can generate multiple signals associated with charge states or adducts, so peak count does not equal compound count. Interpretation involves relating those signals and explaining how the assigned molecular mass was derived.
A reading case: what to check
If a signal cluster appears, ask whether it represents a charge distribution before declaring an impurity mixture. Preserve ionization conditions and deconvolution procedure where available. A coherent calculated mass helps identification but does not replace every structural or purity test the sample may require.
What to preserve in the record
Several peaks may represent charge states or adducts of one entity. An m/z list is not by itself an impurity inventory.
Questions and answers
Am I reading m/z or an already interpreted molecular mass?
A mass spectrometer records ions by mass-to-charge ratio. One species can generate multiple signals associated with charge states or adducts, so peak count does not equal compound count. Interpretation involves relating those signals and explaining how the assigned molecular mass was derived.
What should the review record preserve?
Several peaks may represent charge states or adducts of one entity. An m/z list is not by itself an impurity inventory.
Sources
- Electrospray ionization for mass spectrometry of large biomolecules.
- Anion effects on sodium ion and acid molecule adduction to protein ions in electrospray ionization mass spectrometry.
- Effects of solvent on the maximum charge state and charge state distribution of protein ions produced by electrospray ionization.