Mass spectral analysis of chemical samples is often carried out by obtaining a sample to be analyzed at a sampling site and transporting the sample to the location of the mass spectrometer, which is commonly a large instrument, made immobile by the need for heavy magnets, complex electronics and vacuum systems and a considerable and stable power supply. Furthermore, mass spectrometer performance, in general, benefits from a stable environment.
Typically, mass spectrometers are constructed using conventional magnetic and electric deflection mass analyzers and quadruple mass analyzers. These analyzer types require careful control of magnetic and electric fields. In the case of field deflection instruments, careful alignment and stability along the beam path is required. Minor deformations caused by physical and thermal stress have a deleterious effect on performance of the ion optics. Relatively high operating voltages e.g., in the range of over 1000 V are generally required for a field deflection scanning system of typical mass range. In the case of quadruples, precisely controlled RF power is required for stable operation.
Cycloid mass analyzers separate ions in a region having, at right angles, a magnetic field and an electric field. Typically, the magnetic field is supplied by a heavy permanent magnet. The electric field is induced in the magnet gap by a series of plates held at controlled potentials. Sample ions injected into the crossed-field region follow a spiral path, defined by their mass to charge ratio (m/e), toward the region where a detector is positioned. Variation of the electric field allows mass scanning.
Newton et al. in "A Portable Mass Spectrometer for Field and Laboratory Use" Lawrence Livermore Laboratory Report, Jul. 7, 1975 discloses a "portable" mass spectrometer system employing a cycloid mass analyzer constructed from a commercial instrument. The system requires electrical power from an external source. For experiments in remote areas, the system can be transported by air and installed in a trailer.