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Hitzemann M, Kirk AT, Lippmann M, Nitschke A, Burckhardt O, Winkelholz J, Zimmermann S. High-Resolution Drift Tube Ion Mobility Spectrometer with Ultra-Fast Polarity Switching. Anal Chem 2024; 96:14630-14638. [PMID: 39190505 PMCID: PMC11391402 DOI: 10.1021/acs.analchem.4c03296] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/29/2024]
Abstract
Besides safety and security applications, ion mobility spectrometry (IMS) is increasingly used in other fields such as medicine, environmental monitoring and food quality analysis. However, some applications require gas chromatographic separation before analysis by IMS. Furthermore, different compounds in the sample may form positive or negative ions during ionization and therefore simultaneous detection of both ion polarities is highly beneficial to avoid two chromatographic runs of the same sample. This can be achieved by ultra-fast polarity switching of a single drift tube IMS, allowing for quasi-simultaneous detection of both ion polarities. By using a ramped aperture voltage during the switching process, we overcome the issue of excessive displacement currents at the detector during polarity switching, which usually lead to overdriving the output signal of the high-gain transimpedance amplifier. Furthermore, mechanical aperture grid oscillations caused by polarity switching were also reduced through the ramped aperture voltage. This enables a polarity switching time of only 7 ms at a drift voltage of 8 kV and a drift length of 103 mm, leading to a high resolving power of RP = 117. Requiring 50 ms to acquire a pair of positive and negative spectrum, the IMS achieves an acquisition rate of 20 Hz. It reaches limits of detection of 20 pptv for dimethyl methylphosphonate and 40 pptv for methyl salicylate. For demonstration, different hop varieties were investigated and could be clearly differentiated by considering both, the positive and negative spectra.
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Affiliation(s)
- Moritz Hitzemann
- Institute of Electrical Engineering and Measurement Technology, Department of Sensors and Measurement Technology, Leibniz Universität Hannover, Appelstr. 9A, Hannover 30167, Germany
| | - Ansgar T Kirk
- Institute of Electrical Engineering and Measurement Technology, Department of Sensors and Measurement Technology, Leibniz Universität Hannover, Appelstr. 9A, Hannover 30167, Germany
| | - Martin Lippmann
- Institute of Electrical Engineering and Measurement Technology, Department of Sensors and Measurement Technology, Leibniz Universität Hannover, Appelstr. 9A, Hannover 30167, Germany
| | - Alexander Nitschke
- Institute of Electrical Engineering and Measurement Technology, Department of Sensors and Measurement Technology, Leibniz Universität Hannover, Appelstr. 9A, Hannover 30167, Germany
| | - Olaf Burckhardt
- Institute of Electrical Engineering and Measurement Technology, Department of Sensors and Measurement Technology, Leibniz Universität Hannover, Appelstr. 9A, Hannover 30167, Germany
| | - Jonas Winkelholz
- Institute of Electrical Engineering and Measurement Technology, Department of Sensors and Measurement Technology, Leibniz Universität Hannover, Appelstr. 9A, Hannover 30167, Germany
| | - Stefan Zimmermann
- Institute of Electrical Engineering and Measurement Technology, Department of Sensors and Measurement Technology, Leibniz Universität Hannover, Appelstr. 9A, Hannover 30167, Germany
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Kobelt T, Lippmann M, Wuttke J, Wessel H, Zimmermann S. Influence of ionization volume and sample gas flow rate on separation power in gas chromatography-ion mobility spectrometry. J Chromatogr A 2024; 1713:464506. [PMID: 37983986 DOI: 10.1016/j.chroma.2023.464506] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2023] [Revised: 10/11/2023] [Accepted: 11/10/2023] [Indexed: 11/22/2023]
Abstract
In this work, the influence of the sample gas flow rate and the ionization region volume of an ion mobility spectrometer (IMS) used as a detector in gas chromatography (GC) on GC-IMS peak shape has been investigated. Therefore, a drift tube IMS with a field-switching ion shutter, a defined ionization region volume and an ultra-violet radiation source was used. To identify the influence of the sample gas flow rate entering the ionization region (equals the GC carrier gas flow rate if no further make-up gas is used) and the ionization region volume on peak broadening and signal intensity, different sample volumes as they would elute from a GC were tested at a variety of sample gas flow rates at a given ionization region volume. The results clearly show that for low sample gas flow rates a depletion of sample molecules in the ionization region leads to a significant decrease in effective detector volume but also to reduced signal intensities. Therefore, for optimal performance of a GC-IMS, the optimal operating point of the GC should match the flow range, where the IMS provides the best compromise between signal-to-noise ratio and peak broadening.
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Affiliation(s)
- Tim Kobelt
- Department of Sensors and Measurement Technology, Institute of Electrical Engineering and Measurement Technology, Leibniz University Hannover, Appelstr. 9A, Hannover 30167, Germany.
| | - Martin Lippmann
- Department of Sensors and Measurement Technology, Institute of Electrical Engineering and Measurement Technology, Leibniz University Hannover, Appelstr. 9A, Hannover 30167, Germany
| | - Jannik Wuttke
- Department of Sensors and Measurement Technology, Institute of Electrical Engineering and Measurement Technology, Leibniz University Hannover, Appelstr. 9A, Hannover 30167, Germany
| | - Hanno Wessel
- Department of Sensors and Measurement Technology, Institute of Electrical Engineering and Measurement Technology, Leibniz University Hannover, Appelstr. 9A, Hannover 30167, Germany
| | - Stefan Zimmermann
- Department of Sensors and Measurement Technology, Institute of Electrical Engineering and Measurement Technology, Leibniz University Hannover, Appelstr. 9A, Hannover 30167, Germany
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Li X, Wang H, Jiang M, Ding M, Xu X, Xu B, Zou Y, Yu Y, Yang W. Collision Cross Section Prediction Based on Machine Learning. Molecules 2023; 28:molecules28104050. [PMID: 37241791 DOI: 10.3390/molecules28104050] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2023] [Revised: 05/10/2023] [Accepted: 05/10/2023] [Indexed: 05/28/2023] Open
Abstract
Ion mobility-mass spectrometry (IM-MS) is a powerful separation technique providing an additional dimension of separation to support the enhanced separation and characterization of complex components from the tissue metabolome and medicinal herbs. The integration of machine learning (ML) with IM-MS can overcome the barrier to the lack of reference standards, promoting the creation of a large number of proprietary collision cross section (CCS) databases, which help to achieve the rapid, comprehensive, and accurate characterization of the contained chemical components. In this review, advances in CCS prediction using ML in the past 2 decades are summarized. The advantages of ion mobility-mass spectrometers and the commercially available ion mobility technologies with different principles (e.g., time dispersive, confinement and selective release, and space dispersive) are introduced and compared. The general procedures involved in CCS prediction based on ML (acquisition and optimization of the independent and dependent variables, model construction and evaluation, etc.) are highlighted. In addition, quantum chemistry, molecular dynamics, and CCS theoretical calculations are also described. Finally, the applications of CCS prediction in metabolomics, natural products, foods, and the other research fields are reflected.
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Affiliation(s)
- Xiaohang Li
- State Key Laboratory of Component-Based Chinese Medicine, Tianjin University of Traditional Chinese Medicine, 10 Poyanghu Road, Tianjin 301617, China
- Haihe Laboratory of Modern Chinese Medicine, Tianjin University of Traditional Chinese Medicine, 10 Poyanghu Road, Tianjin 301617, China
| | - Hongda Wang
- State Key Laboratory of Component-Based Chinese Medicine, Tianjin University of Traditional Chinese Medicine, 10 Poyanghu Road, Tianjin 301617, China
- Haihe Laboratory of Modern Chinese Medicine, Tianjin University of Traditional Chinese Medicine, 10 Poyanghu Road, Tianjin 301617, China
| | - Meiting Jiang
- State Key Laboratory of Component-Based Chinese Medicine, Tianjin University of Traditional Chinese Medicine, 10 Poyanghu Road, Tianjin 301617, China
- Haihe Laboratory of Modern Chinese Medicine, Tianjin University of Traditional Chinese Medicine, 10 Poyanghu Road, Tianjin 301617, China
| | - Mengxiang Ding
- State Key Laboratory of Component-Based Chinese Medicine, Tianjin University of Traditional Chinese Medicine, 10 Poyanghu Road, Tianjin 301617, China
- Haihe Laboratory of Modern Chinese Medicine, Tianjin University of Traditional Chinese Medicine, 10 Poyanghu Road, Tianjin 301617, China
| | - Xiaoyan Xu
- State Key Laboratory of Component-Based Chinese Medicine, Tianjin University of Traditional Chinese Medicine, 10 Poyanghu Road, Tianjin 301617, China
- Haihe Laboratory of Modern Chinese Medicine, Tianjin University of Traditional Chinese Medicine, 10 Poyanghu Road, Tianjin 301617, China
| | - Bei Xu
- State Key Laboratory of Component-Based Chinese Medicine, Tianjin University of Traditional Chinese Medicine, 10 Poyanghu Road, Tianjin 301617, China
- Haihe Laboratory of Modern Chinese Medicine, Tianjin University of Traditional Chinese Medicine, 10 Poyanghu Road, Tianjin 301617, China
| | - Yadan Zou
- State Key Laboratory of Component-Based Chinese Medicine, Tianjin University of Traditional Chinese Medicine, 10 Poyanghu Road, Tianjin 301617, China
- Haihe Laboratory of Modern Chinese Medicine, Tianjin University of Traditional Chinese Medicine, 10 Poyanghu Road, Tianjin 301617, China
| | - Yuetong Yu
- State Key Laboratory of Component-Based Chinese Medicine, Tianjin University of Traditional Chinese Medicine, 10 Poyanghu Road, Tianjin 301617, China
| | - Wenzhi Yang
- State Key Laboratory of Component-Based Chinese Medicine, Tianjin University of Traditional Chinese Medicine, 10 Poyanghu Road, Tianjin 301617, China
- Haihe Laboratory of Modern Chinese Medicine, Tianjin University of Traditional Chinese Medicine, 10 Poyanghu Road, Tianjin 301617, China
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Hitzemann M, Schaefer C, Kirk AT, Nitschke A, Lippmann M, Zimmermann S. Easy to assemble dielectric barrier discharge plasma ionization source based on printed circuit boards. Anal Chim Acta 2023; 1239:340649. [PMID: 36628746 DOI: 10.1016/j.aca.2022.340649] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2022] [Revised: 11/14/2022] [Accepted: 11/20/2022] [Indexed: 11/29/2022]
Abstract
Here, we present a new and an easy to assemble dielectric barrier discharge plasma ionization source based on printed circuit boards with two parallel isolated electrodes for generating a plasma inside an inert fused silica capillary. For demonstration, this plasma source is coupled to an ion mobility spectrometer. With two different sample gas feeds the analytes can either pass through the plasma or bypass the plasma before entering the reaction region of the ion mobility spectrometer, allowing for different ionization pathways, e.g. electron impact ionization, ionization by excited species, e.g. helium metastables, or chemical ionization via reactant ions generated inside or downstream of the plasma. The plasma source, in particular, the electrode geometry and the capillary diameter were designed with the help of electric field simulations. A rectangular electrode with a height of at least twice the outer diameter of the capillary turned out to be ideal, in both the simulation and the experiment. Furthermore, a simple control electronics has been developed, which can be easily applied to other plasma sources. With the plasma source presented here, detection limits in the mid pptv range have been reached.
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Affiliation(s)
- Moritz Hitzemann
- Leibniz University Hannover, Institute of Electrical Engineering and Measurement Technology, Appelstr. 9A, 30167, Hannover, Germany.
| | - Christoph Schaefer
- Leibniz University Hannover, Institute of Electrical Engineering and Measurement Technology, Appelstr. 9A, 30167, Hannover, Germany
| | - Ansgar T Kirk
- Leibniz University Hannover, Institute of Electrical Engineering and Measurement Technology, Appelstr. 9A, 30167, Hannover, Germany
| | - Alexander Nitschke
- Leibniz University Hannover, Institute of Electrical Engineering and Measurement Technology, Appelstr. 9A, 30167, Hannover, Germany
| | - Martin Lippmann
- Leibniz University Hannover, Institute of Electrical Engineering and Measurement Technology, Appelstr. 9A, 30167, Hannover, Germany
| | - Stefan Zimmermann
- Leibniz University Hannover, Institute of Electrical Engineering and Measurement Technology, Appelstr. 9A, 30167, Hannover, Germany
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Kirk AT, Kueddelsmann MJ, Zimmermann S. Ultrasensitive Ion Source for Drift Tube Ion Mobility Spectrometers Combining Optimized Sample Gas Flow with Both Chemical Ionization and Direct Ionization. Anal Chem 2022; 94:9960-9969. [PMID: 35793469 DOI: 10.1021/acs.analchem.2c00955] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Efficient ionization of analyte molecules is a crucial step for the outstanding sensitivity of ion mobility spectrometers (IMS) used for trace gas detection. Here, we present a new ion source that combines the previously published extended field switching ion shutter with two switchable ionization sources and an optimized sample gas flow that leads to a focused laminar stream through the reaction region of the ion source. The X-ray ionization source allows for chemical gas phase ionization of analyte molecules, while the UV ionization source allows for direct ionization of analyte molecules. The optimized sample gas flow not only allows for quickly washing out analyte molecules from the reaction region but also has improved sensitivity by a factor of about 5 for protonated monomers, 20 for proton-bound dimers, and over 100 for the proton-bound trimer of 1-octanol. The resulting limits of detection using chemical X-ray ionization are in the subpptv-range for protonated monomers and in the low pptv-range for proton-bound dimers, while the limits of detection using direct UV ionization are in the subppbv-range. Especially, a direct comparison between chemical and direct ionization of ketones using this ultrasensitive ion source reveals a stepwise conversion from directly ionized monomers to proton-bound dimers via protonated monomers during direct UV ionization.
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Affiliation(s)
- Ansgar T Kirk
- Leibniz University Hannover, Institute of Electrical Engineering and Measurement Technology, Department of Sensors and Measurement Technology, 30167 Hannover, Germany
| | - Maximilian J Kueddelsmann
- Leibniz University Hannover, Institute of Electrical Engineering and Measurement Technology, Department of Sensors and Measurement Technology, 30167 Hannover, Germany
| | - Stefan Zimmermann
- Leibniz University Hannover, Institute of Electrical Engineering and Measurement Technology, Department of Sensors and Measurement Technology, 30167 Hannover, Germany
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Li L, Gu H, Lv Y, Zhang Y, He X, Li P. Ultra-Fast Polarity Switching, Non-Radioactive Drift Tube for the Miniaturization of Drift-Time Ion Mobility Spectrometer. SENSORS (BASEL, SWITZERLAND) 2022; 22:s22134866. [PMID: 35808362 PMCID: PMC9269308 DOI: 10.3390/s22134866] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2022] [Revised: 06/23/2022] [Accepted: 06/27/2022] [Indexed: 06/10/2023]
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.
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Affiliation(s)
| | | | | | | | | | - Peng Li
- Correspondence: ; Tel.: +86-136-562-498-81
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7
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te Brinke E, Arrizabalaga-Larrañaga A, Blokland MH. Insights of ion mobility spectrometry and its application on food safety and authenticity: A review. Anal Chim Acta 2022; 1222:340039. [DOI: 10.1016/j.aca.2022.340039] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2022] [Revised: 06/01/2022] [Accepted: 06/03/2022] [Indexed: 11/01/2022]
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Kabir KMM, Ahmed E, Donald WA. An atmospheric pressure ion funnel with a slit entrance for enhancing signal and resolution in high resolution differential ion mobility mass spectrometry. Analyst 2022; 147:870-879. [PMID: 35136893 DOI: 10.1039/d1an01942b] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Differential ion mobility (DMS) is a versatile ion separation method that is often integrated with mass spectrometry (MS). In DMS, extremely high electric fields are used such that ion mobility depends non-linearly on electric field and thus, ion separations can be more orthogonal to MS than lower field ion mobility-based methods. DMS can have sufficiently high resolution to be used for enantiomer analysis of small molecules and to separate protein ions with peak widths comparable to those obtained for peptides. However, the performance of high resolution DMS-MS can be limited owing to the substantial loss of ions (>10-fold) that can occur upon their transfer from atmospheric pressure (where DMS separation typically occurs) to vacuum through a narrow conductance limited inlet (e.g. capillary) to the MS. Here, results from simulated ion trajectory simulations suggest that in high resolution DMS most ions can be lost by 'crashing' onto the narrow capillary inlet after exiting the DMS separation channel. To enhance DMS sensitivity and resolving power, an integrated DMS-MS interface concept is reported that consists of a slit electrode and a 12-electrode atmospheric pressure ion funnel (APIF). By using an APIF with slit entrance, the simulated ion transmission efficiencies increase by up to 257% for singly charged ions ([DMMP + H]+, [tryptophan + H]+, and [(2-dodecanone)2 + H]+) and by 209% for [ubiquitin + 12H]12+, without compromising resolving power. The use of APIF improves the ion focussing from the DMS exit to the MS capillary to improve sensitivity, and the slit ensures that ion dispersion in the analytically relevant direction perpendicular to the DMS electrodes is restricted to enhance resolution. By narrowing the slit of the DMS-Slit-APIF interface, the DMS resolving power can be increased further by at least 20%. Overall, these results indicate that the integrated DMS-Slit-APIF interface is promising for improving the sensitivity and resolution for many different types of DMS-MS experiments.
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Affiliation(s)
- K M Mohibul Kabir
- School of Chemistry, University of New South Wales, Sydney, NSW 2052, Australia.
| | - Ezaz Ahmed
- School of Chemistry, University of New South Wales, Sydney, NSW 2052, Australia.
| | - William A Donald
- School of Chemistry, University of New South Wales, Sydney, NSW 2052, Australia.
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Hitzemann M, Kirk AT, Lippmann M, Bohnhorst A, Zimmermann S. Miniaturized Drift Tube Ion Mobility Spectrometer with Ultra-Fast Polarity Switching. Anal Chem 2022; 94:777-786. [DOI: 10.1021/acs.analchem.1c03268] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Moritz Hitzemann
- Department of Sensors and Measurement Technology, Institute of Electrical Engineering and Measurement Technology, Leibniz Universität Hannover, 30167 Hannover, Germany
| | - Ansgar T. Kirk
- Department of Sensors and Measurement Technology, Institute of Electrical Engineering and Measurement Technology, Leibniz Universität Hannover, 30167 Hannover, Germany
| | - Martin Lippmann
- Department of Sensors and Measurement Technology, Institute of Electrical Engineering and Measurement Technology, Leibniz Universität Hannover, 30167 Hannover, Germany
| | - Alexander Bohnhorst
- Department of Sensors and Measurement Technology, Institute of Electrical Engineering and Measurement Technology, Leibniz Universität Hannover, 30167 Hannover, Germany
| | - Stefan Zimmermann
- Department of Sensors and Measurement Technology, Institute of Electrical Engineering and Measurement Technology, Leibniz Universität Hannover, 30167 Hannover, Germany
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