Matrix-assisted laser desorption electrospray ionization (MALDESI)
is a method for creating ions
that can be used for chemical analysis
in a mass spectrometer
. It is related to desorption electrospray ionization
(DESI) and is a combination of matrix-assisted laser desorption ionization
(MALDI) and electrospray ionization
How it works
In MALDESI, a pulsed laser
is fired at a sample to desorb
material as particles
. The sample is typically at atmospheric pressure
and ambient temperature
. As with MALDI, the sample to be analyzed is mixed with a matrix material that absorbs the laser energy and aids in the laser removal of material. The neutral material interacts with charged droplets in the electrospray plume to form ions that are sampled by a mass spectrometer.
Some samples form ions without the need for a matrix. The technique called electrospray-assisted laser desorption/ionization (ELDI) uses an ultraviolet
laser to form ions by irradiating the sample sample directly for ion formation through interaction with the electrospray plume. The infrared laser version of ELDI has been called laser ablation electrospray ionization (LAESI) or, alternately, infrared laser assisted desorption electrospray ionization (IR-LADESI).
In early versions of thermospray, an infrared laser was directed at a liquid spray tip to heat the sample and aid in ionization. Desorption atmospheric pressure photoionization (DAPPI) uses a jet of heated solvent for desorption and ultraviolet light for photoionization.