Quadrupole ion trap mass spectrometry

Localising Charged Particles by Electric and Magnetic Fields
the trapping of charged particles
Prepared By : Mohamed Fayed Mohamed Ali
Email : [email protected]

1. Localising Charged Particles by Electric and Magnetic Fields the trapping of charged particles Quadrupole Ion Trap Mass Spectrometry Prepared By : Mohamed Fayed Mohamed Ali Email : [email protected]

2. Transmits one m/z ion at a time Mass-Selective Stability scanning Trap all m/z ions simultaneously Mass-Selective Instability scanning Quadrupole Ion Trap In full scan ion traps are more sensitive than quadrupoles. quadrupoles use SIM to enhance sensitivity Filter Bucket Quadrupole vs. Ion Traps Quad. Ion Trap • RF fields yield m/z band of stability •3DManipulation of trajectory •Detect those ions that are selectively ejected due to destabilized trajectory •Pulsed analysis Quadrupole •RF fields yield m/z band of stability •2DManipulation of trajectory •Detect those ions that are selectively transmitted with stable trajectories •Continuous analysis

3. The quadrupole ion trap, also known as the Paul trap, was first described in 1954. It is a high performance technique and one of the leading tools in the chemistry and biochemistry fields It can be used for measurements of very high mass/charge ratios Ion trap mass spectrometry has high resolution capabilities and also excellent non-destructive broad-band Fourier transform capabilities

4. Ions are subjected to stabilizing and destabilizing forces applied by the field. The forces occur in three dimensions. The ion trap can hold up to 105-106 ions before columbic repulsions reduce the mass resolution The diagram which illustrates the ion trap instrumentation

5. Introduction A quadrupole ion trap consists of three hyperbolic electrodes – one ring electrode and two identical end-cap electrodes (the ring electrode),(the entrance endcap electrode ),( the exit endcap electrode). The central electrode is the rotationally symmetrical ring electrode and it is located between two end-cap electrodes of the same cross-section The ring electrode is located halfway between the two endcap electrodes. The end-cap electrodes contain an aperture on each electrode center for ion injection and ejection. Both endcap electrodes have a small hole in their centers through which the ions can travel. The ion-trap mass spectrometer uses three electrodes to trap ions in a small volume. The mass analyzer consists of a ring electrode separating two hemispherical electrodes. A mass spectrum is obtained by changing the electrode voltages to eject the ions from the trap. The advantages of the ion-trap mass spectrometer include compact size, and the ability to trap and accumulate ions to increase the signal-to-noise ratio of a measurement.

6. #Confinement of Ions The purpose of an atom or ion trap is to confine the motion of the atomic or ionic particles to a small region of space. Confinement of the ions in the Penning trap is achieved by adding a constant magnetic field along the z-axis to the electrostatic field Three Dimensional Confinement The three-dimensional quadrupole trap field given by a three-electrode structure as shown in the Figure. There are two end-cap electrodes separated by a distance 2z0 and a ring electrode of radius r o , (r2 0 = 2z2 0 ) whose surfaces are hyperboloids of revolution about the z-axis. r is the internal radius of the ring electrode z is the closest distance from the center to the end-cap electrodes. + z o r o For trapping the positive ions the two end-caps are held at a static positive potential with the ring electrode held at negative potential. At the trap center, the potential between the end caps and the ring electrodes forms a saddle and the charged particles will be confined either in the radial plane or in the axial direction, but will escape in the other direction

7. In quadrupole ion trap operation Ions produced from the source enter the trap through the inlet focusing system and the entrance endcap electrode. Various voltages are applied to the electrodes to trap and eject ions according to their mass-to-charge ratios. The ring electrode RF potential, an a.c . potential of constant frequency and variable amplitude, is applied to the ring electrode to produce a 3D quadrupolar potential field within the trapping cavity. This will trap ions in a stable oscillating trajectory confined within the trapping cell. The nature of the trajectory is dependent on the trapping potential and the mass-to-charge ratio of the ions. During detection, the electrode system potentials are altered to produce instabilities in the ion trajectories and thus eject the ions in the axial direction. The ions are ejected in order of increasing mass-to-charge ratio, focused by the exit lens and detected by the ion detector system.

8. In quadrupole ion trap operation The electrodes are hyperboloidal with a radial r0 and axial z0 dimension, respectively . r0 is the inner radius of the ring electrode and z0 is the distance from the trapping center to one of the end-cap electrodes. Ideally, the relationship between the radial and axial dimension should be: r0 = 2z02 A radio frequency (RF) voltage is applied to the ring electrode to create a three-dimensional trapping field. In quadrupole ion trap operation, a radiofrequency (RF) waveform and DC offset voltage are applied on the ring electrode to create a time varying electric field. In addition, an alternating current (AC) waveform, or ground could be applied on the end-cap electrodes depending on the analysis method. Consequently, ions are trapped in the trapping region due to a pseudopotential well. In the simplest mass analysis mode, the parameters of the trap (such as RF voltage) are scanned such that ions are sequentially ejected based on the mass-to-charge ratio (m/z).

9. MS/MS in an Ion Trap 1. Inject 2. Isolate 3. Fragment 4. Detect This trapping and analysis are analogous to a bowl filled with layers of liquids of different densities. Upon tilting the bowl, the upper layer liquid, corresponding to the ions of lowest mass-to-charge ratio is poured first from the bowl). Continuing with the analogy, the bowl continues to be tilted by ramping the RF amplitude, so that the ions with different mass-to-charge ratio are ejected out of the trap to the detector at different times. Lastly, ion signals are recorded as a mass spectrum.

10. High sensitivity Capable of high performance Compactness and mechanical simplicity Ion/Molecule reactions can be studied for mass-selected ions and the reaction time can be varied in the ion trap. Therefore, the kinetics and equilibrium of ion-molecule reactions can be studied High resolution for slow scans The resonance experiments are applicable in the study of ions that have high m/z ratios Fourier transform techniques provide non-destructive detection MS/MS experiments are possible (multiple stage mass spectrometry). In these experiments, individual ions can be examined in a mixture of ions. The ions of interest are isolated by their characteristic m/z values and they dissociate. The product ions are then analyzed in a second mass measurement step. Advantages of using ion trap:

11. REFERENCES QUANTUM INFORMATION PROCESSING WITH TRAPPED ION CHAINS Timothy Andrew Manning, Doctor of Philosophy, 2014 Miniaturization of Linear Ion Traps and Ion Motion Study in a Toroidal Ion Trap Mass Analyzer : Ailin Li Brigham ,Young University ,2017-08-01 Mass Spectrometry Principles and Applications Third Edition Edmond de Hoffmann Universit´e Catholique de Louvain, Belgium & Ludwig Institute for Cancer Research, Brussels, Belgium Vincent Stroobant Ludwig Institute for Cancer Research, Brussels, Belgium QUADRUPOLE ION TRAP MASS SPECTROMETRY Second Edition RAYMOND E. MARCH Trent University, Peterborough, Ontario, Canada JOHN F. J. TODD University of Kent, Canterbury, UK A JOHN www.thermofisher.com