Mass spectrometry is a technique that is used to analyze different elements in solids, liquids and gasses. Identification, quantification and profiling of possible molecules, isotopes and molecule complexes can be achieved. As such the chemical composition of the sample can be deducted.
The process of mass spectrometry consists roughly of three phases: ionizing, mass separation and detection. During the ionizing phase an electrical charge gets applied to the gassified sample in order to ionize the molecules in the sample. Techniques include:
- Fast atom bombardment (FAB);
- Chemical ionization (CI);
- Atmospheric-pressure chemical ionization (APCI);
- Electrospray ionization (ESI);
- Matrix-assisted laser desorption/ionization (MALDI);
- Glow discharge;
- Field desorption (FD);
- Thermospray, desorption/ionization on silicon (DIOS);
- Direct Analysis in Real Time (DART);
- Secondary ion mass spectrometry (SIMS);
- Spark ionization and thermal ionization (TIMS).
In the mass separation phase the different elements get separated based on the mass/charge ratio (m/z). Depending on the ionization technique one of the following methods are used:
- Sector instruments;
- Time-of-flight (TOF);
- Quadrupole mass filter;
- Three-dimensional quadrupole ion trap;
- Linear quadrupole ion trap;
- Fourier transform ion cyclotron resonance (FTMS).
Next in the final phase, detection, the amount of ions are counted. The detection of these ions can be achieved through different means. This can be done by letting the ions crash into a screen or let them fly past one. By doing this a current or charge can be induced. Then the amplified signals can be translated to the relative abundance of certain m/z values.
This will result in a plot of a mass spectrum, which is a representation of the intensity plotted against the m/z ratio. By using a library of mass spectra tables or computer algorithms researchers can deduct the components of the sample.
Combination with LabVIEW
Wizzo has developed a LabVIEW driver for a specific mass spectrometer, Pfeiffer Vacuum's GSD320/QMG220. This driver can be used to start or stop a measurement on the mass spectrometer, as well as start and stop the filament.
While running a measurement the data will be read from the mass spectrometer with the corresponding mass values. Once the test has ended or stopped, the data can be presented in a report and/or exported to a data analysis system (Osisoft's PI, LabWare's LIMS) or a database.
Several suppliers of different types of mass spectrometers:
- Perkin Elmer
- Pfeiffer Vacuum
- MassTech's AP MALDI
- Hitachi High-Technologies