Techniques Available

The following page outlines the the techniques routinely available on the mass spectrometry service.

Which Ionisation Method?
To try to avoid unnecessary duplication and delays to results being returned please try to determine the ionisation method that works best for your type of compounds and submit the samples for that method first. If we cannot get a result, we will try other methods. In simplest terms, EI is the highest energy technique, with CI being better for less stable compounds. Both of these technique require the sample to be volatile and non-labile. ESI and MALDI are the lowest energy techniques and are best for more complex, labile, non-volatile compounds. The following table is a guide to the ionisation techniques available:

Ionisation Technique Abbreviation Mass Range* Polarity Instrument(s) Typical Resolution Typical Mass Accuracy
Electron Ionisation EI 100-850 Da +ve Autospec 3,500 < 5 ppm
Chemical Ionisation CI 100-850 Da +ve Autospec 3,500 < 5ppm
Electrospray Ionisation ESI m/z 100-6000 +ve/-ve Esquire 6000
no acc-mass
< 1ppm internal, < 3ppm external
< 2ppm
Nanospray Ionisation
m/z 100-3000 +ve/-ve Synapt <20,000 < 2ppm
Matrix-assisted Laser
MALDI 100-500,000 +ve/-ve ABI4700
no acc-mass
< 5ppm

* the mass range depends on the instrument used. For ESI and nanospray, multiple charging greatly extends the molecular weight range that can be analysed.