Ultra-Fast Polarity Switching, Non-Radioactive Drift Tube for the Miniaturization of Drift-Time Ion Mobility Spectrometer

Abstract

Drift-time ion mobility spectrometer (DT-IMS) is a promising technology for gas detection and analysis in the form of miniaturized instrument. Analytes may exist in the form of positively or negatively charged ions according to their chemical composition and ionization condition, and therefore require both polarity of electric field for the detection. In this work the polarity switching of a drift-time ion mobility spectrometer based on a direct current (DC) corona discharge ionization source was investigated, with novel solutions for both the control of ion shutter and the stabilization of aperture grid. The drift field is established by employing a switchable high voltage power supply and a serial of voltage regulator diode, with optocouplers to drive the ion shutter when the polarity is switched. The potential of aperture grid is stabilized during the polarity switching by the use of four diodes to avoid unnecessary charging cycle of the aperture grid capacitor. Based on the proposed techniques, the developed DT-IMS with 50 mm drift path is able to switch its polarity in 10 ms and acquire mobility spectrum after 10 ms of stabilization. Coupled with a thermal desorption sampler, limit of detection (LoD) of 0.1 ng was achieved for ketamine and TNT. Extra benefits include single calibration substance for both polarities and largely simplified pneumatic design, together with the reduction of second drift tube and its accessories. This work paved the way towards further miniaturization of DT-IMS without compromise of performance.

Implementing of Fourier Deconvolution Multiplexing to Fast Polarity Switching Miniaturized Ion Mobility Spectrometer

“…At the end of the drift tube, a stainless-steel grid was placed 1 mm from the faraday plate. A full-bridge rectifier was connected between the aperture grid and ground as described in previous reports , to stabilize the voltage applied to the aperture grid during the polarity switching process. The ion signals received on the Faraday plate are amplified 5 × 10 8 by a customized ADA4530-1 based two-stage preamplifier and transmitted to the data acquisition (DAQ) device.…”

Non-Contact, Continuous Sampling of Porous Surfaces for the Detection of Particulate and Adsorbed Organic Contaminations by Low-Temperature Plasma Coupled to Ion Mobility Spectrometer

“…Due to the complexity of sampling such surfaces, such mapping is performed mainly by sampling the vapors to a field portable detector, such as an ion mobility spectrometer (IMS), mass spectrometry (MS), and flame photometric detector (FPD) [ 1 , 2 , 3 , 4 ]. Numerous works demonstrated the use of such techniques combining desorption methods for the detection and mapping of explosives and drugs [ 5 , 6 ], toxic industrial compounds [ 7 ], volatile organic compounds (VOC) [ 8 ] and chemical warfare agents [ 9 ]. Sampling is based on collecting a minute amount of vapors released from the analyte or wiping an area of a few square centimeters with a swab, followed by thermal desorption of the collected sample.…”

Fluorescent Photoelectric Detection of Peroxide Explosives Based on a Time Series Similarity Measurement Method

“…However, the detection time of the electrochemical method was long, and the detection could not be performed in a portable manner. Li designed an ultra-fast polarity-switching ion mobility spectroscopy (IMS) drift tube with a non-radioactive ionization source, and employed novel methods in the electronic design to switch the aperture grid and ion shutter, with the detection limit of 0.1 ng [9]. Mamo reported an electrospray ionization ion mobility spectrometer with both positive and negative ion modes capable of detecting explosives such as ammonium nitrate (AN), TNT, and TATP [10].…”