Mass Accuracy in Peptide Mass Spectrometry
Mass accuracy describes how closely an observed mass matches the expected value.
Reporting error
Mass error may be reported in daltons or parts per million. Parts per million helps compare errors across molecular sizes.
Influencing factors
- calibration
- instrument resolution
- signal intensity
- charge-state assignment
- isotope selection
- temperature stability
- space-charge effects
- deconvolution settings
External and internal calibration
External calibration uses a separate standard. Internal calibration uses a known signal within the same spectrum and can improve local accuracy.
Frequently asked questions
Is lower ppm always better?
Generally, but required accuracy depends on intended use.
Can a correct mass still represent the wrong sequence?
Yes. Isobaric sequences and stereoisomers may share mass.
Why does low signal reduce accuracy?
The centroid of a weak peak is less reliably determined.
Can calibration drift during a run?
Yes. Bracketing checks can detect drift.
Key takeaways
Mass accuracy strengthens identity assignments, but it does not independently prove sequence order, purity, or stereochemistry.
References
- Aebersold R, Mann M. Mass-spectrometric exploration of proteome structure and function. Nature. 2016.
- Gross JH. Mass Spectrometry: A Textbook. Springer.
TSMS Labs educational disclaimer: For laboratory research and educational purposes only. Not for human consumption. This content is not medical, clinical, or regulatory advice.