An Introduction to Mass Spectrometry (cont.)

The second technique electrospray ionization (ESI) creates ions by application of a potential to a flowing liquid causing the liquid to charge and subsequently spray.

The electrospray creates very small droplets of solvent-containing analyte. Solvent is removed as the droplets enter the mass spectrometer by heat or some other form of energy (e.g. energetic collisions with a gas), and multiply-charged ions are formed in the process. The detection limits that can be achieved with ESI have improved with a reduction in the flow rates and hence the use of small diameter columns to achieve separations at low flow rates. A typical nanoelectrospray source is shown below.

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