Location
- Research Support Building (CACTUS)
- Rúa de Constantino Candeira, 1. Campus Vida , 15782Santiago de Compostela
- Phones
- 881 816 242
As the droplets evaporate rapidly, either by a desorption process of the electric field or by evaporation of the solvent, the analyte molecules approach each other, repel each other, and finally, when the repulsion of the charges overcomes the surface tension, the droplets explode (Coulomb explosion). Protonated molecules are thus released into the gas phase and move into the mass analyser. The ions generated can be multiply prototyped, giving rise to different species for the same molecule, even forming adducts with an alkali metal such as sodium or potassium.
The ionisation mechanism in Electrospray in both positive and negative modes is as follows.
Being an equilibrium process, in the case of positive ionisation, the ionisation reaction is enhanced by using solutions with weak acids such as formic or acetic acid. Therefore, polar molecules containing basic sites in their structure are accommodated for this type of technique and polarity. In the case of negative ionisation, it is suitable for analytes with functional groups that deprotonate easily (carboxyl or sulphonic groups).
The Electrospray technique has 3 characteristics that differentiate it from other mass spectrometric ionisation techniques:
- Unique ability to produce ions with multiple charges, thus allowing very high molecular weight compounds (e.g. proteins) to be recorded with multiple charges in a much smaller m/z range.
- Samples must be introduced in solution, thus enabling a natural compatibility between ESI with separation techniques such as HPLC/UHPLC chromatography.
- This is a particularly ‘soft’ technique, with very little fragmentation, which enables the preservation in the gas phase of non-covalent interactions between molecules, which exist in solution, as well as the study of molecular conformations in three dimensions.
Mass Spectrometry and Proteomics Unit
- Research Support Building (CACTUS)
- Rúa de Constantino Candeira, 1. Campus Vida , 15782Santiago de Compostela
- 881 816 242