Linear Time-of-Flight Mass Spectrometers

Comstock's LTOF-110 Linear Time-of-Flight Mass Spectrometer

See our Mini-TOF^®II 

Features:

• Wide mass range (0 to 5000)
• Rapid Acquisition of mass spectral information (the entire spectrum is acquired in under 500 microseconds)
• High sensitivity
• Simple operation
• Compatibility with numerous other techniques (gas chromatography, molecular beams, secondary ion mass spectrometry, MALDI)
• Second order spatial focussing ionization source

Applications:

• Fast Gas Chromatography (Fast GC)
• Gas Analysis
• Laser Ionization Spectroscopy Experiments
• Thermal Desorption Mass Spectrometry

• Perfluorophenanthrene, Calibration compound, include peak table showing mass accuracy

Specifications:

LTOF-110	Laser Ionization Source	Electron Impact Ionization Source
Mass Range	0 to 5,000 amu	0 to 5,000 amu
Mass Resolution (m/dm)	300 to 800	500
Mass Accuracy	better than 150 ppm	better than 150 ppm
Flight Tube Length	1 meter (custom lengths available)	1 meter (custom lengths available)
Electron Gun	-	-
Electron Energy	-	5 to 150 eV
Energy Resolution	-	700 meV
Current (at 70 eV)	-	200 microamperes

System Summary

The linear configuration of time-of-flight mass spectrometers is the simplest implementation of the time-of-flight technique. Linear time-of-flight mass spectrometers provide moderate mass resolution and outstanding sensitivity and spectra acquisition speed. The acquisition cycle of time-of-flight mass spectrometers is pulsed. In linear time-of-flight mass spectrometers, ions are either prepared within or injected into the ion source and are accelerated to the detector. The resulting signal is a transient where the lightest m/z ions arrive at the detector first. The detector used is capable of providing gain sufficient for observation of a single ion. The basic elements of the LTOF-110 are: ionization source, flight tube with ion optics, and detector. Comstock's linear time-of-flight mass spectrometers can be used for analysis of gases with LI or EII; solids using Thermal Desorption, LDI, or MALDI; or liquids using an electrospray source.

Ionization Sources

Comstock's LTOF-110 Spectrometers are available with ion sources configured for laser ionization (LI) or electron impact ionization (EII). The electron impact ionization source can also be used as a laser ionization source.

All ionization sources use Comstock's proprietary second order spatial focussing technology that provides optimal mass resolution.

Spectrometer and Ion Optics

Comstock's LTOF-110 time-of-flight spectrometer uses and internal flight tube that can be floated to +/- 5,000 volts for detection of either positive or negative ions. The floated flight tube allows the source to be operated at ground potential making possible the orthogonal injection of ions from an external beam into the source. Vertical and horizontal deflectors and an ion lens are used to guide the ions to the detector.

Detectors

Comstock's LTOF-110 is available with capacitively coupled 50 ohm impedance matched dual chevron microchannel plate detectors or ETP electron multiplier detectors.

Power Supplies

For all applications using the LTOF-110, a TFP-210 power supply is used for application of the necessary voltages to the spectrometer ion optics, flight tube and detector. The different sources require additional power supplies:

• LI: RPS-112 power supply. Provides pulsed or DC voltage to repeller. Pulse width, delay, and amplitude is user selectable.
  EII: RPS-112 and EGP-110 power supplies. RPS-112 as above. EGP-110 for control and power of electron gun. Electron energy, focus, pulse width, repetition rate are user selectable.
• In addition Comstock offers all these voltages in a single convenient package that is computer controlled.

Detection Electronics

Because the signal generated in time-of-flight mass spectrometry is a transient ion signal, high speed digitizers are necessary for capturing the spectra. Comstock offers two basic approaches for waveform capturing: digital storage oscilloscope (DSO) with PC interface or high speed A/D card mounted within the PC. The best performance is gained by use of the DSO while the PC mounted A/D card is less expensive but can transmit the data to the PC much faster.

For applications that require very high dynamic range, Comstock provides a high speed time-to-digital converter for counting ions generated in multiple experimental cycles.

Data System

Comstock's data system is based on Microsoft Windows with Comstock's software, which is written in National Instruments' LabWindows language. Comstock's data system provides computer control of all aspects of instrumental function and power and data acquisition.

Chambers, Pumping, Mounting

Comstock's LTOF-110 vacuum system is composed of two chambers: a source chamber and a flight tube chamber. Pumping options include turbo-molecular pumps or diffusion pumps. For system configurations requiring a high gas load in the source chamber, a conductance limited mounting scheme is used to provide differentially pumped zones. The LTOF-110 is mounted on a floor standing enclosure with a formica work surface, power distribution system, and a power supply instrument mounting rack.

Options

• Mass Gate
• Thermal Desorption Probe
• Laser Desorption Probe
• Delayed Pulse Extraction
• Post Accelerator for efficient high mass detection
• Molecular Beam Source
• High Temperature Gas Chromatography Interface
• Membrane Introduction Source