Cluster Chemistry and Energy Catalysis Research Group organizes Q Exactive training on May 15, 2024

The Thermo Scientific Q Exactive Combination Quadrupole Orbitrap Mass Spectrometer is equipped with a high-performance quadrupole and a high-resolution, accurate mass number (HRAM) Orbitrap detector.Q Exactive Combination Quadrupole Orbitrap Mass Spectrometer Structure

The Q Exactive Combined Quadrupole Orbitrap Mass Spectrometer consists of an ion source, stacked loop ion guide (S-lens), quadrupole mass filter, curved linear trap (C-trap), high-energy collisional dissociation (HCD) chamber, and Orbitrap mass analyzer. Samples can be introduced into the ion source by a variety of methods. Injection of the flatapole transfers ions from the ion source to the quadrupole. The quadrupole assembly acts as an ion transfer device that filters the transferred ions based on mass-to-charge ratio. The ions are transferred into the C-Trap, which is then injected into the Orbitrap mass analyzer to obtain a mass spectrogram. In addition, the ions pass through the C-Trap into the HCD chamber and are combined with a quadrupole mass filter for MS/MS experiments.

In the Q Exactive, an atmospheric pressure ionization (API) source forms gas phase sample ions and is used as a link between liquid chromatography (LC) and MS.The API ion source consists of a maximum ion source and an ion source interface. The Maximum Ion Source can be configured for different API modes including Atmospheric Pressure Chemical Ionization (APCI), Atmospheric Pressure Photoionization (APPI), and Electrospray Ionization (ESI).The NSI model can be obtained by using a separate Nano Spray Ionization (NSI) probe. The ESI, APCI, and APPI probes can be interchanged without the use of tools by installing the ion source mount on the front. The Ion Source Interface consists of an ion transport capillary (to aid in ion desolvation), two cartridge heaters, a heater block, a platinum probe sensor, an anti-exhaust balloon (to prevent air from entering the vacuum manifold), an ion purge cone (to direct purge gases to the inlet of the tubes), a tube lens, and a skimmer.

Ion optics

Ion optics focuses ions generated in an ion source and transfers the ions to a C-trap.The injection flatapole is a square array of flat metal electrodes used as an ion focusing device. The curved flatapole transmits ions from the injection flatapole to the quadrupole through a 90-degree arc, removing neutral gas jets and solvent droplets. A combination of internal and external Turner-Kruger (TK lenses) focus the ion beam into the quadrupole and act as a vacuum baffle between the bent flatapole and the quadrupole. The quad exit lens focuses the ions from the quadrupole into the transfer multipole, which acts as another transfer device. The separation lens is used to start and stop the injection of ions into the mass analyzer. The S-lens in the source region increases the transfer of ions to the Q Exactive instrument, increasing the scan rate by decreasing the ion injection time or increasing the sensitivity by injecting more ions when the ion injection time reaches its maximum (maximum ion time).

Quadrupole Mass Filter

A quadrupole is a square array of hyperbolic contoured circular rods located between the TK lens and the transfer multipole. In a quadrupole, two opposite rods in the array are electrically connected.RF and DC voltages are applied to the rods. Voltages of the same amplitude and sign are applied to each pair of rods, but voltages applied to different rod pairs have the same amplitude but opposite sign.The ratio of RF to DC voltages and their values determine the range of mass-to-charge ratios (m/z) transferred through the quadrupole mass filter. For each injection controlled by the separating lens, the quadrupole RF amplitude and DC voltage were set to fixed values. Under these conditions, only ions with a certain range of m/z ratios will remain within bounded oscillations as they pass through the mass filter.

Bending the linear trap

Ions entering the C-trap may lose kinetic energy by colliding with the nitrogen collision gas (bath gas) to prevent them from leaving the C-trap through the gate.The nitrogen collision gas is used to dissipate the kinetic energy of the injected ions and cool them down to the axis of the C-trap.Voltages on the end holes (inlet and outlet holes) of the C-trap are elevated to provide the potential traps along its axis. These voltages may then be gradually increased to squeeze the ions into shorter lines along this axis.

HCD Chamber

Sample ions can be passed through the C-trap into the HCD collision chamber, which consists of a straight multipole mounted inside a metal tube. The front part of the tube is equipped with a lens to regulate the transmission and injection of the C-trap. A potential gradient was applied to the collision chamber for rapid ion extraction. Fragmentation spectra generated in the HCD chamber and detected in the Orbitrap show fragmentation patterns comparable to typical triple quadrupole mass spectra.

Orbitrap Mass Analyzer

The heart of the Orbitrap Mass Analyzer is an axisymmetric mass analyzer consisting of a spindle-shaped center electrode surrounded by a pair of bell-shaped external electrodes. In the Orbitrap mass analyzer, stable ion trajectories combine rotation around the axial center electrode with harmonic oscillations generated along the axis. The frequency of these harmonic oscillations along the z-axis depends only on the m/z of the ion and the instrument. Ions of all m/z were extracted to the mass analyzer for image current detection. The two halves of the outer electrode detect the image currents generated by the oscillating ions. The instrument obtains the frequency of these axial oscillations and thus the m/z of the ions by Fourier transform.

Q Exactive Combination Quadrupole Orbitrap Mass Spectrometer Features

1. resolution of up to 140,000 allows more peaks to be seen in the sample, increasing the reliability of results when analyzing samples in complex matrices.

2. Fast scan-to-scan polarity switching in MS and MS/MS to find more compounds in a single run.

3. S-Lens in the source region can increase sensitivity by injecting more ions into the instrument.

4. Spectrum multiplexing and advanced signal processing ensure UHPLC-compatible data acquisition speeds for increased throughput.

5. Q Exactive Combination Quadrupole Orbitrap Mass Spectrometer Applications

Other references are detailed:

https://zhuanlan.zhihu.com/p/330268885