ESI-MS - Electrospray Ionisation Mass Spectrometry

Electroscopy Ionisation (ESI) is a ‘soft’ ionisation technique used in mass spectrometry to generate ions using electrometry, by applying a high voltage to a liquid to create an aerosol.

This technique is particularly useful in ionising large biological molecules, such as proteins for analysis without fragmenting them.

Required Material:

• Sample

• Solvent

• Mass spectrometer

• Electrospray ionisation source

Sample preparation:

Purified samples work best, which are then injected into the electrospray ionization mass spectrometer through a capillary needle.

1. First dissolve the sample in an organic solvent to a 1mg/ml concentration.

2. From the solution take 10µl and mix with 1ml of methanol, acetonitrile, or water.

3. Filter the solution to ensure there is no precipitation, as it can cause blockage.

Protocol:

1. Set up the ESI source according to the manufacturer’s instructions or your requirements.

2. Load the sample via a capillary needle, the solution then becomes infused into the ESI source.

3. The sample is ionised, causing the molecules to be ejected from the solution in the form of charged droplets.

4. Charged droplets are desolvated leaving behind charged analyte ions.

5. The analyte ions are analysed by the mass spectrometer, which separates the ions based on the mass-to-charge ratio (m/z).

6. The results can be interpreted using different software programs that are programmed to identify sample components, quantification, and statistical analysis.