Fourier-Transform MS and Closed-Path Multireflection Time-of-Flight MS Using an Electrostatic Linear Ion Trap

Abstract

An electrostatic linear ion trap (ELIT) has been configured to allow for the simultaneous acquisition of mass spectra via Fourier transform (FT) techniques (frequency measurement) and via time-of-flight (TOF; time measurement). In the former case, the time-domain image charge derived from a pick-up electrode in the field-free region of the ELIT is converted to frequency-domain data via Fourier transformation (i.e., FT-ELIT MS). In the latter case, the time difference between ion injection into the ELIT and ion detection after release from the ELIT using a microchannel plate (MCP) enables the acquisition of multireflection time-of-flight mass spectra (MR-TOF MS). The ELIT geometry facilitates the acquisition of both types of data simultaneously because the detection schemes are independent and do not preclude one another. The two MS approaches exhibit a degree of complementarity. Resolution increases much faster with time with the MR-TOF approach, for example, but the closed-path nature of executing MR-TOF in an ELIT limits both the m/z range and the peak capacity. For this reason, the FT-ELIT MS approach is most appropriate for wide m/z range applications, whereas MR-TOF MS can provide advantages in a "zoom-in" mode in which moderate resolution (M/ΔM ≈ 10000) at short analysis times (10 ms) is desirable.

Simultaneous Isolation of Nonadjacent m/z Ions Using Mirror Switching in an Electrostatic Linear Ion Trap

“…The nanoelectrospray ionization (nESI) source and the method by which ions are concentrated and injected into the electrostatic linear ion trap (ELIT) have been described previously, and a brief description is provided in the Supporting Information . Procedures for obtaining mass spectra via Fourier transformation (FT) have been described, and a short summary is provided in the Supporting Information . On the basis of the gain of our detection circuitry, the number of charges associated with the experiments described herein is estimated to be on the order of 5000.…”

“…All experiments were carried out on a home-built 5.25″ ELIT that has been described previously. 16 The nanoelectrospray ionization (nESI) source and the method by which ions are concentrated and injected into the electrostatic linear ion trap (ELIT) have been described previously, and a brief description is provided in the Supporting Information. 17 Procedures for obtaining mass spectra via Fourier transformation (FT) have been described, and a short summary is provided in the Supporting Information.…”

“…17 Procedures for obtaining mass spectra via Fourier transformation (FT) have been described, and a short summary is provided in the Supporting Information. 16 On the basis of the gain of our detection circuitry, the number of charges associated with the experiments described herein is estimated to be on the order of 5000.…”

Mirror Switching for High-Resolution Ion Isolation in an Electrostatic Linear Ion Trap

“…17 Mass analysis can be achieved via MR-TOF using an external detector following release from the ELIT or Fourier transform mass spectrometry (FTMS), 26 using a pick-up electrode within the ELIT for image current detection, or both. 27 A serious potential complication for both mass analysis and ion isolation using a closed-path MR-TOF device, however, is the so-called "race track effect" 28 whereby fast ions lap slow ions leading to ambiguity in mass selection/determination. Herein, we describe and demonstrate a general approach to achieving high-resolution (>10 000) ion isolation with high efficiency (i.e., little or no ion loss) using multiple mirror switching pulses with an ELIT.…”

“…ELIT that has been described previously. 27 The nanoelectrospray ionization (nESI) source and the method by which ions are concentrated and injected into the ELIT have been described previously, and a brief description is provided in the Supporting Information. 29 Procedures for obtaining mass spectra via Fourier transformation and via MR-TOF with this device have been described, 25 and a summary is provided in the Supporting Information.…”