Study of the ionization mechanism in hybrid laser based desorption techniques

In order to study the ionization mechanism in MALDESI, the RASTIR source was implemented to separate in space the laser desorption event from the intersecting electrospray ionization beam. Deuterated solvents were electrosprayed from the RASTIR source which resulted in a near complete shift from [M + H(+)](1+) to [M + D(+)](1+) of the monoisotopic peak for reserpine. The purpose of these experiments is to test the hypothesis that the primary ionization pathway in MALDESI is through interaction of the laser-desorbed neutral species with the intersecting electrospray ionization beam. The combination of RASTIR coupled to MALDESI can be utilized to study small organic molecules as well as peptides and proteins. Moreover, the use of RASTIR combined with MALDESI lends itself to improve the overall efficiency of ionization.