Ion-mobility spectrometry–mass spectrometry
The separated ions are then introduced into a mass analyzer in a second step where their mass-to-charge ratios can be determined on a microsecond timescale.
[1] The effective separation of analytes achieved with this method makes it widely applicable in the analysis of complex samples such as in proteomics and metabolomics.
[1] In the early 1960s, he coupled a low-field ion mobility drift cell to a sector mass spectrometer.
Their work was later reproduced in the landmark book of Mason/McDaniel, which is regarded as the “bible of IMS” by those skilled in the art.
In 1997 Tanner patented a quadrupole with axial fields which can be used as a drift cell for IMS separation.
[6] This work led to the development of an ion mobility-quadrupole-CID-TOFMS instrument by Micromass in the UK and ultimately led Micromass / Waters corporation to develop of the world's first commercial ion mobility-mass spectrometer instrument in 2006.
Many ionization methods similar to those traditionally used for mass spectrometry have been employed for IM-MS depending on the physical state of the analyte.
Therefore, FAIMS is usually coupled with triple quadrupole mass spectrometer which is also ion selection type instrument.
In TWIMS, ions are separated according to their mobility through a travelling wave in a gas filled cell.
Both radio-frequency (RF) and direct current (DC) voltages are applied to a series of ring electrodes called a stacked ring ion guide (SRIG) to confine the ions and create a travelling wave.
Similar to DTIMS, CCS values of ions can be calculated with TWIMS using a calibration derived with known standards.
[1] The TOF-MS has many advantages including the high speed of data acquisition and good sensitivity.
[10] Additionally, hybrid mass spectrometers have been interfaced to more than one ion mobility cell for tandem or IMSn–MSm applications.
[16] The IM-MS technique can be used for analyzing complex mixtures based on differing mobilities in an electric field.
[20] Recently, gas phase ion activation methods have been used to gain new insights into complex structures.
