Compact EI-TOFMS for Rapid And Sensitive Gas Analysis
The Kore compact EI-TOFMS is a modular time-offlight mass analyser that is available in various forms including a bench-top version (shown) or in transportable versions. It provides rapid and sensitive gas analysis for production and research applications. The compact EI-TOFMS's ease of operation and ability to produce stable long-term measurements of the constituents of gases at pressures from millibars to 10 bars makes the equipment well suited to process monitoring as well as catalysis studies and reaction kinetics research.
Gas Inlet System
The instrument can be fitted with a 16 port multi-position valve for process gas analysis. Other inlet options include a Single Capillary inlet for rapid (<1 second) continuous high sensitivity analysis of inorganic gases as well as being ideally suited to couple to a Gas Chromatograph (e.g. PREFICS) as a fast MS GC detector. The GC can be integrated into the instrument if required. A dual switchable membrane inlet/ capillary inlet for organic gas sensitivity and inorganic gas detection can also be provided.
The Mass Spectrometer
At the heart of the instrument is a time-of-flight mass spectrometer with the well-known virtues of parallel detection, mass accuracy and high transmission (sensitivity).
In the compact EI-TOFMS a separately pumped Electron Impact (EI) ion source feeds a small TOF-MS via transfer optics in an orthogonal geometry. Electron impact (EI) ionisation is the best-known method for producing ions and thus gives data, which can be interpreted with well-established techniques and compared against extensive libraries using, automated methods. For example, the NIST EI mass spectral database contains over 100,000 common compounds with many facilities for search and library organisation.
Using the mass resolution and mass accuracy of a TOF-MS it is possible to separate common organic and inorganic interferences and more readily identify unknowns. Similarly the TOF-MS has a large mass range from 1-2000 amu ensuring that all gases of interest can be detected.
The TOF-MS system used in the compact EI-TOFMS is highly attractive because it offers real-time, high time resolution, high sensitivity detection of all gas species in parallel. All masses are collected, preserving the maximum amount of information.
The fundamental measurement 'unit' of the instrument is a mass spectrum. The instrument will generate a single mass spectrum from less than 0.5 seconds to many minutes' duration if required. Rapid spectral acquisition is key for verifying the correct operation of the instrument, and for deciding how to proceed further with the experiment of interest.
High Time Resolution Mode
For short duration experiments (typically up to 20 minutes) it is possible to stream the information of all detected ions to disk, and then 'replay' the data with as fine an experiment time resolution as the user wants (and the counting statistics permit). In this mode for instance, it is possible to request full mass spectra at time slices of as little as 100ms. Alternatively, one might request the time evolution plot of any species with a time resolution of 100ms. This type of functionality is useful for extracting the most information from short-term experiments, and is done using existing GC-MS tools within the GRAMS software package.
Process Monitor Mode
Where the experiment takes places over many hours or even days, it is not practical to run the instrument continually and store every recorded ion to disk. Instead, the user requests that a mass spectrum of x seconds duration be acquired every y seconds of elapsed time. The instrument then operates in a mode where selected species are plotted 'live' to a graph as a function of elapsed experiment time- essentially a process monitor type operation.
For the live plot, species are specified before hand in a set-up table. At each data point a full mass spectrum may be saved to disk, and so at the end of the experiment the user may reconstruct the time evolution of any mass species at the time resolution dictated by the frequency of data recording in the experiment.
The Data System
Data is displayed on a PC, using the Windows® based GRAMS/AI™ software from Thermo Galactic Corporation. This industry standard software has been customised by Kore to make the collection of spectra a simple press of a screen button. Kore provides a spectrum library with library search facilities and data analysis software for the automatic analysis of mixtures that presents the identified sample gas components concentrations in tabular form. The software allows the user to monitor trends in multiple gases over long periods of time.
- Mass range
- 1-2000 amu
- Mass resolution
- 1000 M/dM FWHM at mass 30
- Mass accuracy
- ± 10 milli amu of the peak centroid
- Measuring time
- Full mass spectrum in 100msec time slots
- Dynamic range
- 6 decades
- Better than 1%
- Xenon in ambient air 90ppb in 1 minute
- Inlet system
- Single capillary, or dual switchable membrane/capillary inlet, or 16 port multi-position valve. Millibar to 10 bar pressure gas inlet, or GC inlet.
- Power supply
- 100-230 V, max 750 W
- Ethernet 100Mb/sec
- Bench-top version: 870 x 540 x 380 (depth, width, height) mm
Last updated : 16:36 17/02/2014
© Kore Technology Limited 2014