IMS Instrumentation I: Isolated data acquisition for ion mobility spectrometers with grounded ion sources
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ORIGINAL RESEARCH
IMS Instrumentation I: Isolated data acquisition for ion mobility spectrometers with grounded ion sources Martin Lippmann 1
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Ansgar T. Kirk 1
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Moritz Hitzemann 1
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Stefan Zimmermann 1
Received: 6 March 2020 / Revised: 6 March 2020 / Accepted: 22 April 2020 # The Author(s) 2020
Abstract The drift voltage required for operating ion mobility spectrometers implies high voltage isolation of either the ion source or the detector. Typically, the detector is grounded due to the sensitivity of the small ion currents to interferences and thus higher requirements for signal integrity than the ion source. However, for certain ion sources, such as non-radioactive electron emitters or electrospray ionization sources, or for coupling with other instruments, such as gas or liquid chromatographs, a grounded ion source is beneficial. In this paper, we present an isolated data acquisition interface using a 16 bit, 250 kilosamples per second analog to digital converter and fiber optic transmitters and receivers. All spectra recorded via this new data acquisition interface and with a grounded ion source show the same peak shapes and noise when compared with a grounded detector, allowing additional freedom in design. Keywords Ion mobility spectrometer . Data acquisition . Amplifier . Isolated . Floating . Grounded ion source
Introduction Ion mobility spectrometers (IMS) separate and characterize ions based on their motion under the influence of an electric field. Their possible analytical performance is directly related to the available drift voltage affecting both the resolving power and the signal-to-noise-ratio [1–5]. Typical drift voltages of ion mobility spectrometers are several kilovolts, requiring one end of the drift tube to be referenced to high voltage. Usually, the detector is at ground potential and the ion source is at high potential, as shown in Fig. 1, to avoid isolating the sensitive ion current signal. However, for certain applications this is not the optimum configuration. For example, ionization sources requiring more complex driver electronics, such as non-radioactive electron emitters [6–8] or X-ray sources [9, 10]. Furthermore, other instruments such as gas chromatographs (GC) with heated transfer lines [11, 12], liquid chromatographs (LC) [13] or syringe pumps for direct electrospray ionization (ESI) [14, * Martin Lippmann [email protected] 1
Institute of Electrical Engineering and Measurement Technology, Department of Sensors and Measurement Technology, Leibniz University Hannover, Appelstr. 9A, 30167 Hannover, Germany
15] often require to be referenced to ground potential. Finally, a dual drift tube IMS for simultaneously recording both ion polarities [16, 17] requires at least one of the two detectors at high potential, as it is not possible to extract both the positive and negative ions from the ion source with two grounded detectors. Thus, in this paper we will discuss a simple isolated data acquisition interface, measuring the ion currents at high potential thus a
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