External Second Gate, Fourier Transform Ion Mobility Spectrometry: Parametric Optimization for Detection of Weapons of Mass Destruction

Abstract

Ion mobility spectrometry (IMS) is recognized as one of the most sensitive and robust techniques for the detection of narcotics, explosives and chemical warfare agents. IMS is widely used in forensic, military and security applications. Increasing threat of terrorist attacks, the proliferation of narcotics, Chemical Weapons Convention (CWC) treaty verification as well as humanitarian de-mining efforts have mandated that equal importance be placed on the time required to obtain results as well as the quality of the analytical data.[1] In this regard IMS is virtually unrivaled when both speed of response and sensitivity have to be considered.[2] The problem with conventional (signal averaging) IMS systems is the fixed duty cycle of the entrance gate that restricts to less than 1%, the number of available ions contributing to the measured signal. Furthermore, the signal averaging process incorporates scan-to-scan variations that degrade the spectral resolution contributing to misidentifications and false positives. With external second gate, Fourier Transform ion mobility spectrometry (FT-IMS) the entrance gate frequency is variable and can be altered in conjunction with other data acquisition parameters (scan time and sampling rate) to increase the spectral resolution to reduce false alarms and improve the sensitivity for early warning and contamination avoidance. In addition, with FT-IMS the entrance gate operates with a 50% duty cycle and so affords a seven-fold increase in sensitivity. Recent data on high explosives are presented to demonstrate the parametric optimization in sensitivity and resolution of our system.

Review on Ion Mobility Spectrometry. Part 2: hyphenated methods and effects of experimental parameters

“…A better way of describing peak quality is through its aspect ratio 116 AR , or the ratio of the peak height h to the width at the base w b : $$AR=\frac{h}{w_b}$$ …”

Fourier transform ion mobility spectrometry with multinozzle emitter array electrospray ionization

“…[11][12][13] Historically, Fourier transform ion mobility spectrometry (FT-IMS) was the rst multiplexing ion mobility method used to improve the IMS duty cycle. [14][15][16] By applying a synchronized frequency sweeping square wave to two Bradbury-Nielsen (BN) gates installed at the beginning and the end of the dri region, the duty cycle of FT-IMS was improved to 25%, producing an ion current interferogram. The interferogram could be transformed to an ion mobility spectrum by fast Fourier transform (FFT).…”

Ion spectrometric detection technologies for ultra‐traces of explosives: A review

“…Other advantages over conventional IMS include improved signal-to-noise ratio, eliminations of peak tailing and elimination of the averaging of measurement cycles (Tarver, 2004). Coupled with a vapor generator, three explosives (TNT, RDX, and PETN) have been employed for calibration purposes in IMS (Davies et al, 1993).…”