Pushing LDI-IM-oTOF interface to its limits: Theoretical and Experimental ionic cluster studies using selective collisional-energy transfer.

摘要

With the advent of coupled Ion Mobility-Mass Spectrometry (IM-MS) over the past decade, a convenient tool for probing the structures of small molecules has become available [1,2]. The most important factor involved in the successful implementation of IM-MS in the field of proteomics is the incorporation of simultaneous tandem MS following IM separation (IM-MS/MS). The ions may be formed through a variety of processes, but it is perhaps the molecular fragmentation pattern that produces much of the analytical power of the technique. Mass-to-charge ratios are recorded and the structure of the parent ion may be determined from the ion molecular mass, the collision cross section and the pattern of the fragment ions recorded. In order to perform a high throughput analyses, we report for the first time the use of a (MA)LDI-IM-CID-oTOF instrument for small molecule characterization (up to 1700 Da). Ions produced by a (MA)LDI source are separated by their collision cross section in an ion mobility cell, followed by simultaneous fragmentation and mass-to-charge characterization of the parent and fragment ions (IM-CID-MS). The ion fragmentation is performed using an aperture/electrostatically focusing drift tube combination, that results in a controlled pressure gradient region in which the ion energy can be tuned to sequentially activate different dissociation channels and, at the same time, focus the parent and fragment ions to further be analyzed by their mass-to-charge ratios.