Ion mobility spectrometry
Even though it is used extensively for military or security objectives, such as detecting drugs and explosives, the technology also has many applications in laboratory analysis, including studying small and big biomolecules.
[citation needed] IMS was first developed primarily by Earl W. McDaniel of Georgia Institute of Technology in the 1950s and 1960s when he used drift cells with low applied electric fields to study gas phase ion mobilities and reactions.
Since then, IMS cells have been included in various configurations of mass spectrometers, gas chromatographs, and high-performance liquid chromatography instruments.
IMS is a method used in multiple contexts, and the breadth of applications that it can support, in addition to its capabilities, is continually being expanded.
[5] As a research tool, ion mobility is becoming more widely used in the analysis of biological materials, specifically proteomics and metabolomics.
For example, IMS-MS using MALDI as the ionization method has helped make advances in proteomics, providing faster high-resolution separations of protein pieces in analysis.
[6] Moreover, it is a really promising tool for glycomics, as rotationally averaged collision cross section (CCS) values can be obtained.
CCS values are important distinguishing characteristics of ions in the gas phase, and in addition to the empirical determinations, it can also be calculated computationally when the 3D structure of the molecule is known.
This way, adding CCS values of glycans and their fragments to databases will increase structural identification confidence and accuracy.
[8][9] In industrial settings, uses of IMS include checking equipment cleanliness and detecting emission contents, such as determining the amount of hydrochloric and hydrofluoric acid in a stack gas from a process.
For precise control of the ion pulse width admitted to the drift tube, more complex gating systems such as a Bradbury–Nielsen or a field switching shutter are employed.
Ions are recorded at the detector in order from the fastest to the slowest, generating a response signal characteristic for the chemical composition of the measured sample.
Due to the vastly reduced number of ion-neutral interactions, much longer drift tubes or much faster ion shutters are necessary to achieve the same resolving power.
Calibrants can help circumvent this major drawback, however, these should be matched for size, charge and chemical class of the given analyte.
[23] TIMS operates in the pressure range of 2 to 5 hPa and replaces the ion funnel found in the source region of modern mass spectrometers.
A DMA can separate charged aerosol particles or ions according to their mobility in an electric field prior to their detection, which can be done with several means, including electrometers or the more sophisticated mass spectrometers.
A novel design for corona discharge ionization ion mobility spectrometry (CD–IMS) as a detector after capillary gas chromatography has been produced in 2012.
In addition to the practical conveniences in coupling the capillary to IMS cell, this direct axial interfacing helps us to achieve a more efficient ionization, resulting in higher sensitivity.
[33] A DMD is often a type of microelectromechanical system, radio frequency modulated ion mobility spectrometry (MEMS RF-IMS) device.
For instance, it was incorporated by Varian in its CP-4900 DMD MicroGC, and by Thermo Fisher in its EGIS Defender system, designed to detect narcotics and explosives in transportation or other security applications.
Coupled with LC and MS, IMS has become widely used to analyze biomolecules, a practice heavily developed by David E. Clemmer, now at Indiana University (Bloomington).
[3][36] IMS has commonly been attached to several mass spec analyzers, including quadropole, time-of-flight, and Fourier transform cyclotron resonance.
