Methods / Laser Based Techniques

Laser Desorption/Ionization is currently often used in many labs with the assistance of matricies. However, there are many techniques being developed here that utilize lasers without the need to use an applied matrix.

On the "micro"-scale

Laser Desorption/Ionization Mass Spectrometry
Coupled with Electrospray Secondary Ionization

Spatial resolution of chemical images obtained using LDI-MS is often limited due to poor ion yields (i.e. ion/neutral yield < 0.01%)
Secondary ionization methods can be used to improve ion yields of LDI-MS by ionizing the more abundant desorbed neutral species
Preliminary results for LDI-MS with ES secondary ionization of neutral species show more than 100 times improvement in ion signal, which should translate to the enhancement of spatial resolution.

On the "nano"-scale

Tip-Enhanced, Near-Field Desorption/Ionization Mass Spectrometry

Conventional Laser Desorption Ionization Mass Spectrometry is limited in spatial resolution by diffraction to about half the wavelength of laser light irradiating the sample. Laser irradiation of a nanoscale probe can create an intensified near-field optical source at the tip 10-100 times smaller in spatial extent than the wavelength of the laser light.

Tip-enhanced, near-field desorption/ionization MS has the potential to improve the spatial resolution of mass spectrometric chemical imaging by at least an order-of-magnitude, and thus has enormous promise as an advanced spectroscopic method for investigating nanoscale structures

Tip-enhanced, near-field LDI-MS in combination with an atomic force microscope (AFM), has the potential for nanoscale MS chemical imaging correllated to topography, and thus has enormous promise as an advanced spectroscopic method for investigating physical and chemical characteristics of nanoscale structures like the active sites on chem/bio sensors.