Orbitrap LC-MS Comparison Chart

Resolution: Frequently reported in full width at half maximum (FWHM), resolution is the separation of two mass spectrometry peaks and is calculated as the mass of a peak (M) divided by resolving power (∆M).

Mass accuracy: Expressed in parts per million, this value indicates how much an instrument deviates from a known standard or calibrant.

Scan rate: Measured in hertz, the scan rate of an MS indicates how quickly it scans a mass spectrum.

Polarity switch: The collection of both positive and negative sample ionization data (spectra) by the ion trap during a single MS analysis. Polarity switching is applied to the study of drugs, drug metabolites, pesticides, etc.

PRM: Parallel reaction monitoring (PRM) is a targeted method of high resolution MS quantification in which a full scan of each precursor ion transition is monitored; i.e., all fragments derived from the precursor ion are monitored. In contrast, single reaction monitoring (SRM) performs one transition monitoring at a time.

Multiplex: The ability of a mass analyzer to acquire data from multiple precursor ions in the same scan without compromising high signal-to-noise ratio.

MSⁿ: Also termed tandem MS, the use of multiple stage MS to capture product ion spectra of a defined m/z, where n is the number of recorded product ion stages.

ETD: Electron transfer dissociation (ETD) results in the fragmentation of the peptide backbone of MS samples, simplifying identification of peptide modification sites.

Synchronous MS³: A method of quantitation that involves simultaneous selection of several MS² precursors for MS³ analysis and is often used during TMT and iTRAQ experiments.