Design of a new electrospray ion mobility mass spectrometer

The design of a new ion mobility mass spectrometer is presented. The design features an electrospray ion source; an ion funnel to transmit ions efficiently from the source to the mobility cell and to accumulate ions in the pulsed ion mode; a mobility cell, and a quadrupole mass analyzer. Each part of the instrument is described in detail. Preliminary results obtained with the new instrument are presented to demonstrate its capabilities. Equilibrium experiments showed that the DeltaG degrees (300 K) values for the addition of the first water molecule to the doubly protonated peptides bradykinin, angiotensin II, and LHRH are in the range from -3.5 to -2.5 kcal/mol. The corresponding values for the singly protonated ions are > -0.5 kcal/mol for angiotensin II and LHRH, but equal to -2.6 kcal/mol for bradykinin. The stronger bonding in bradykinin may be due to the presence of a salt bridge structure. Ion arrival time distributions showed that singly protonated peptides can form aggregates of the form (nM + nH)(n+). The mobilities of these ions indicated that they are near spherical. Heating the drift cell to similar to 450 K caused dissociation of the (2M + 2H)(2-) ion into two (M + H)(+) units on the 1 ms experimental time scale. A theoretical fit to the experimental data yielded rate constants and a barrier for dissociation of 30 +/- 2 kcal/mol for bradykinin and 39 +/- 3 kcal/mol for LHRH. (C) 2001 Elsevier Science B.V.