A new, higher resolution, ion mobility mass spectrometer

Ion mobility spectroscopy (IMS) coupled with mass spectrometry (MS) has become a key tool for investigation of molecular conformation and aggregation. The technique has been widely applied to both biological and inorganic materials. The ability to distinguish isomers with similar shapes (and cross sections) is the critical advantage of IMS. Of equal importance is the ability to distinguish different oligomer states with the same value of m/z (singly charged monomer, doubly charged dimer, etc.). We present here a combined IMS–MS instrument able to resolve structures with cross sections differing by less than 1%. Ions can be produced either by electrospray or MALDI ionization. Ion funnels are used at both the entrance and exit of a 2 m long drift tube. Mass analysis can be done either with a quadrupole or TOF mass spectrometry following the drift tube. The use of a quadrupole mass spectrometer provides very high sensitivity although the mass range is limited. A variety of experiments and applications to several previously studied chemical systems and standard peptides are presented. These include both ESI and MALDI mass spectrums, high resolution ion mobility experiments and identification of oligomeric state through mobility selected mass spectrometry.