Ion mobility spectrometry (IMS) has proven a key technology in advancing molecular characterization of biological and environmental samples for a wide range of scientific applications, such as disease prognosis, environmental monitoring, and detection of warfare agents. An IMS system separates ions from a sample and delivers them to a mass spectrometer for detection. But IMS is generally limited to atmospheric pressure or near-vacuum conditions that involve radio-frequency (RF) electric fields. IMS operating at atmospheric pressure has low resolution because of the practical limitation on the electric field applied. On the other hand, IMS operating at near-vacuum conditions requires the use of a confining chamber and associated vacuum pumps combined with an RF power supply, greatly increasing the size, weight, and cost of operating IMS systems and limiting their use.
Researchers at Pacific Northwest National Laboratory have developed a device to trap, separate, and manipulate ions in a sample at a wide range of pressures, including atmospheric pressure. Atmospheric Pressure Ion Confinement, or APIC, comprises a set of thin, stacked rings adjacent to each other along a central axis. Each ring includes electrodes that together define an enclosed volume holding the ionized sample. The rings can be arranged in a circle, triangle, pentagon, hexagon, octagon, or more complex cyclical arrangements of any number of rings. The rings can also form a T-shape, allowing ions to be switched to either of two paths at the junction.
The electrodes periodically receive a DC voltage to generate a circular traveling wave that rotates around the electrodes of each ring. This wave confines ions within the interior of the device. The device enables complex sequences of ion separations, transfers, path switching, and trapping, resulting in the precise separation of sample constituents. In addition, because APIC uses DC voltage rather than RF, it can operate at atmospheric pressure and attain much higher resolution than typical IMS devices.
APIC can improve ion manipulation in a variety of applications such as separating structural isomers and resolving conformational features of charged chemical compounds, macromolecules, and essentially any charged particles. It can also be used to augment mass spectroscopy in a broad range of applications, including metabolomics, glycomics, and proteomics.
- Operates at virtually any pressure above 0.1 Torr
- Uses oscillatory electric fields to move and separate ions
- Transfers ions efficiently over long pathways