Micromass GCT Orthogonal Acceleration Time-of-Flight (aa-TOF) GC/MS Mass Spectrometer
Comes as seen in photos.
The Micromass GCT is a benchtop, compact, fully integrated, high performance orthogonal acceleration time-of-flight (TOF) mass spectrometer designed for GC-MS and probe MS applications that offers exact mass measurement capabilities. The GCT’s high resolution and mass accuracy allow for the determination of elemental composition and increased specificity for the identification of unknowns. The high full scan sensitivity further extends it capability to profiling of complex chromatograms. High versatility is supplied in the form of various ionization and inlet options. These are GC, EI and CI.
The system consists of a source and analyser housing separated by a pneumatic isolation valve and a differential pumping aperture. The source housing is fitted with a 250 L/sec high compression turbomolecular pump. The analyser housing is fitted with a 70 L/sec high compression turbomolecular pump. A single RV3 rotary pump backs both turbomolecular pumps.
Sample introduction on the GCT instrument occurs using a probe or GC interface. The TOF analyzer enables high resolution (5000-7000) mass measurements with an accuracy of ~5 ppm. EI/CI is most suitable for low molecular weight, low polarity compounds (m/z range ~1500). The probe may be heated to 650°C to vapourize low volatility compounds (although evaporation may be in competition with decomposition).
GCT includes Electron Impact (EI), Chemical Ionisation (CI) and Field Ionisation (FI) source options. The ion source is at ground potential to allow simple direct coupling to the GC inlet, thereby minimising the possibility of cold spots. A source probe allows easy exchange of the EI and CI removable inner volumes, or of the FI emitter.
Ions are accelerated from the grounded ion source to 40eV before being accelerated orthogonally into the time of flight (TOF) mass analyser. The TOF analyser has a two stage orthogonal acceleration region, followed by a single stage reflectron, giving an effective path length of 1.2 meter. Ions are detected using a dual microchannel plate assembly capable of detecting positive or negative ions. Ion arrival times are recorded using a time to digital converter (TDC) with a sampling rate of 1 or 3.6GHz. GCT TM produces high quality, full mass spectra with elevated resolution (~ 7000 FWHM). This elevated resolution reduces the likelihood of mass interferences. Furthermore the precise linear relationship between ion arrival time and the square root of its mass allows good mass measurement accuracy with only a single internal reference mass. The precision of mass measurement can provide elemental composition of unknowns and confirm identification of eluting compounds. The full mass spectral sensitivity of the GCT is comparable to that of a quadrupole mass spectrometer, operating in single ion recording mode and monitoring 10 - 20 masses.
In comparison to a quadrupole instrument when used to record full mass spectra, the GCT can be 10 - 100 times more sensitive, depending on the mass range acquired.