In practical traps, the outer electrode is sustained at virtual ground and a voltage of 3.5 or 5 kV is applied to the inner electrode only. Furthermore, the absence of additional excitation allows the detection process to start as soon as the detection electronics recover from the voltage ramp needed for ion injection.Ĭurrently the Orbitrap analyzer exists in two variants: a standard trap and a compact high-field trap. However, if ion packets are injected away from the minimum of the axial potential (which corresponds to the thickest part of either electrode), this automatically initiates their axial oscillations, eliminating the need for any additional excitation. In principle, coherent axial oscillations of ion rings could be excited by applying RF waveforms to the outer electrode as demonstrated in and references therein. The C-trap is tightly integrated with the analyzer, injection optics and differential pumping. By rapidly ramping down trapping RF voltages and applying DC gradients across the C-trap, ions can be bunched into short packets similar to those from the laser ion source. This method of injection works well with pulsed sources such as MALDI but cannot be interfaced to continuous ion sources like electrospray.Īll commercial Orbitrap mass spectrometers utilize a curved linear trap for ion injection ( C-trap). Proof-of-principle of the technology was carried out using the direct injection of ions from an external laser desorption and ionization ion source.
![what does the orbitron do what does the orbitron do](https://igx.4sqi.net/img/general/600x600/30361888_GIAPuEhwtW7q3-0OH69xiPI32Mo8BeyuxbospUcOgnU.jpg)
This means that ions of a specific mass-to-charge ratio spread into rings which oscillate along the inner spindle. These ions move with different rotational frequencies but with the same axial frequency. At that moment ramping is stopped, the field becomes static, and detection can start.Įach packet contains a multitude of ions of different velocities spread over a certain volume. Ions get squeezed towards the inner electrode until they reach the desired orbit inside the trap. As ion packets are injected tangentially into the field, the electric field is increased by ramping the voltage on the inner electrode. In order to inject ions from an external ion source, the field between the electrodes is first reduced. Its angular frequency is: ω = √ k/( m/ z), where k is the force constant of the potential, similar to the spring constant. it is completely independent not only of motion around the inner electrode but also of all initial parameters of the ions except their mass-to-charge ratios m/z. Due to the properties of the quadro-logarithmic potential, their axial motion is harmonic, i.e. In addition, the ions also move back and forth along the axis of the central electrode so that their trajectories in space resemble helices. Thus, ions cycle around the inner electrode on elliptical trajectories. In the Orbitrap, ions are trapped because their electrostatic attraction to the inner electrode is balanced by their inertia.
![what does the orbitron do what does the orbitron do](https://i1028.photobucket.com/albums/y341/wazobiaenterprise3/MT118/DSC_0115.jpg)
Ion packet enters the analyzer during the voltage ramp and form rings that induce current detected by the amplifier. Principle of operation Ĭross-section of the C-trap and Orbitrap analyzer (ion optics and differential pumping not shown).
![what does the orbitron do what does the orbitron do](https://winter.group.shef.ac.uk/orbitron/atomic_orbitals/3p/3p_dots_512.png)
The invention of the Orbitrap analyzer and its proof-of-principle by Makarov at the end of the 1990s started a sequence of technology improvements which resulted in the commercial introduction of this analyzer by Thermo Fisher Scientific as a part of the hybrid LTQ Orbitrap instrument in 2005. Neither the Kingdon nor the Knight configurations were reported to produce mass spectra. In 1981, Knight introduced a modified outer electrode that included an axial quadrupole term that confines the ions on the trap axis. A static applied voltage results in a radial logarithmic potential between the electrodes. The Kingdon trap consists of a thin central wire and an outer cylindrical electrode.
![what does the orbitron do what does the orbitron do](https://www.planetcarsz.com/assets/uploads/ORBITRON%201964%2008.jpg)
The concept of electrostatically trapping ions in an orbit around a central spindle was developed by Kenneth Hay Kingdon in the early 1920s.