Mass spectrometry is a powerful analytical chemistry tool that detects molecules in the gas phase based on their mass to charge ratio. This session will cover the basic concepts of mass spectrometry, how it works, the components of a mass spectrum, tandem MS (or MS/MS), the relationship between chromatograms and mass spectra, tuning, and what your service representative will do.
This session will use diagrams and animations to lay the foundation for novices to begin building their mass spectrometry knowledge.
The three components of amass spectrometerare the ion source, mass analyzer, and detector. The ion source generates molecular ions that may be separated in the mass analyzer based on their mass to charge (m/z) ratio prior to detection. With a known precursor, the user can calculate predicted m/z values that may be detected via mass spectrometry.
A mass spectrum is intensity or relative abundance (y-axis) vs. m/z (x-axis) of the ions detected. In MS, the spectrum represents precursor molecules, also referred to as parent molecules. With the sensitivity of mass spectrometry, isotopic clusters around the nominal mass can be detected due to the contribution of the natural abundances of elemental isotopes (e.g. 13C is 1.10% of the natural carbon on Earth, 15N is 0.37%). In MS/MS, the spectrum typically represents the fragments of a precursor molecule selected in the mass analyzer.
The total ion chromatogram (TIC) is the ion count (y-axis) vs. time (x-axis). At each time point in the TIC, there is an associated mass spectrum. After data acquisition, data analysis software programs can extract the times when a user-defined mass of interest is detected via MS, yielding an extracted ion chromatogram (EIC or XIC) of ion count (y-axis) vs. time (x-axis).
Learning objectives of this session:
1. Understand how a mass spectrometer separates molecules
2. Calculate m/z and determine charge state of isotopic clusters
3. Recognize a total ion chromatogram, extracted ion chromatogram and mass spectrum
4. Differentiate between MS and MS/MS