Towards Advanced Drift Time Ion Mobility Spectrometry in Security Applications

Ion Mobility Spectrometry (IMS) has found application in points-of-entry security detection. However, most recent advances in mobility have shifted towards vacuum-based methods such as cyclic, SLIM, and Traveling Wave methods. While these advancements have improved the separation characteristics of mobility measurements, they at the cost of increased experimental complexity and expense, specifically through requiring vacuum systems to achieve mobility separation. When applied to point-of-entry, these advances are underutilized, resulting in inferior separation metrics in this critical infrastructure.

Advancements in high-voltage pulsing and high-voltage amplifiers allow the development of the next generation of drift time IMS. Using theoretical considerations in the mobility separation, the potential on an IMS cell may be changed during separation to improve resolution and resolving power without sacrificing experimental time. While the current state-of-the-art requires sophisticated high voltage amplifiers, we demonstrate a custom amplifier circuit capable of achieving potential sweeps at a fraction of the cost. In addition, the ion gating inefficiency have long been a limiting factor in drift time mobility separations for large ions and complex samples. Using a high-voltage pulser, a pulsed nano-ESI may be applied to the IMS cell in lieu of an ion gate. Initial results demonstrate a significant increase in large ion population in the resultant ion swarm and a significant increase in total ion signal without loss of mobility fidelity and resolution in the experiment.

Both IMS and Mass Spectral analysis will confirm ion speciation in the resultant spectra. The combination of the pulsed ion source with a swept potential experiment has the potential to provide simultaneous separation of complex mixtures in a small footprint instrument and these methodologies will provide a new paradigm for operating small footprint, low-cost drift time IMS units.