Note: Integration of trapped ion mobility spectrometry with mass spectrometry

Abstract

The integration of a trapped ion mobility spectrometer (TIMS) with a mass spectrometer (MS) for complementary fast, gas-phase mobility separation prior to mass analysis (TIMS-MS) is described. The ion transmission and mobility separation are discussed as a function of the ion source condition, bath gas velocity, analysis scan speed, RF ion confinement, and downstream ion optical conditions. TIMS mobility resolution depends on the analysis scan speed and the bath gas velocity, with the unique advantage that the IMS separation can be easily tuned from high speed (∼25 ms) for rapid analysis to slower scans for higher mobility resolution (R > 80). © 2011 American Institute of Physics. [doi:10.1063/1.3665933] Ion mobility spectrometry (IMS) coupling to mass spectrometry offers several advantages over traditional mass spectrometry (MS), including separation of ions from mixtures based on composition and charge state, the ability to separate geometric isomers, increased dynamic range, and discrimination against chemical noise. 1 Several research groups have focused on achieving high resolution IMS separation (R > 50) as this factor mainly limits the information that can be experimentally derived. In a different IMS approach, the use of a trapped ion mobility spectrometer (TIMS) device for fast, gas-phase separation of molecular isobar pairs has been recently described. 1 In the present note, we describe the TIMS-MS integration and its advantage over traditional drift tube based IMS-MS designs; discussion is also focused on the factors that influence TIMS-MS mobility separation, dynamic range, and versatility.In the example presented here, ions were generated by electrospray ionization (ESI) using an ESI ion source based on the Apollo II design (Bruker Daltonics Inc., MA). Accordingly, a quadrupolar funnel optic was used and the capillary coupling the ESI spray chamber to the first pumping stage was orthogonal to the axis of the TIMS analyzer. Each TIMS electrode is composed of four electrically isolated segments. In the entrance and exit funnel sections, a RF-induced pseudopotential keeps the ions away from the funnel walls (180 • out of phase between adjacent plates). However, in the analyzer section, the phase of the RF potential does not alternate between adjacent plates but only between adjacent segments. The RF field (typically 950 kHz and 200-400 Vpp) plays little or no direct role in the mobility analysis. The operating pressure difference (P1 = 2.6-3.4 and P2 = 2.6 mbars) produces a cylindrically symmetric gas flow of nitrogen at ∼300 K. After exiting the TIMS analyzer, ions are focused, using a series of lenses and a hexapole ion guide, through the main differential pumping region. In this transfer area, residual pressure drops from 2.6 mbars in the first funnel to 10 −4 mbars in the a) Author to whom correspondence should be addressed. Electronic mail: ffernandez@chem.tamu.edu.hexapole. After the transfer area, ions enter the quadrupole mass analyzer (Q), which can be operated in transmission or isolation...

Kinetic Intermediates of Holo- and Apo-Myoglobin Studied Using HDX-TIMS-MS and Molecular Dynamic Simulations

“…With the recent development of trapped ion mobility spectrometry (TIMS) [37, 38], higher mobility separation [39, 40] and the possibility to interrogate and simultaneously measure the ion-neutral collision cross section (CCS) as a function of the time after the molecular ion formation (gas-phase time after desolvation or trapped time in the TIMS) has permitted kinetic studies of molecular ions in the millisecond to second time scale as well as the influence of the collision partner on the conformational space accessible to the molecular ions in the gas phase [41, 42]. In the current study, the unique potential of TIMS to hold ions while interacting with bath gas molecules (“TIMS” thermostat) is utilized to study the folding motifs of holo- and apoMb by measuring the CCS and HDX under the same folding conditions (e.g., solvent conditions and time after molecular ion formation).…”

Ion Mobility Collision Cross Section Compendium

“…These have included updates to traveling wave instrumentation (TWIMS), new uniform field drift tubes (DTIMS) operated at both elevated 1 and reduced pressures (less than 10 Torr), 2–4 and a newly-developed ion trapping device operated in a mobility-selective mode (trapped ion mobility spectrometry, TIMS) 5–7 . Other ion mobility techniques including cyclic and extended path length traveling wave devices are currently in development.…”

Altering the mobility-time continuum: nonlinear scan functions for targeted high resolution trapped ion mobility-mass spectrometry

“…Details of the instrumentation can be found in the literature [24][25][26][27][28][29][30]. Briefly, ions were produced by electrospray ionization (ESI) at atmospheric pressure.…”