AN ION-TRAP INTERFACE FOR ESI-ION MOBILITY EXPERIMENTS

A method for improving the sensitivity of ion mobility measurements of ions generated from continuous ionization sources such as electrospra y ionization is described. The method involves an ion trap interface b etween the continuous source and the pulsed experiment. The trap allow s the electrosprayed ion beam to be accumulated between pulses of the mobility experiment and provides tightly focused (both spatially and t emporally) ion pulses for initiating experiments. Using this method, w e have improved signal-to-noise ratios by factors of similar to 10-30 compared with those of existing approaches and achieved experimental d uty cycles of nearly 100%. With these improvements, it is possible to record complex ion mobility distributions in less than 10 s, and we ha ve obtained detection limits of 1.3 pmol for the oligosaccharide malto tetraose. A detailed description of the experimental arrangement is gi ven. An application of the improved methods in which collision-induced fragmentation of biomolecules is monitored by ion mobility spectromet ry is described.