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Derpmann V, Müller D, Haack A, Wissdorf W, Kersten H, Benter T. Charging Effects in Inlet Capillaries. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2022; 33:1678-1691. [PMID: 36001770 DOI: 10.1021/jasms.2c00130] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Glass or metal inlet capillaries are commonly used for flow restriction in atmospheric pressure ionization mass spectrometers. They exhibit a high ion transmission rate and stability at most operating conditions. However, transferring unipolar currents of ions through inlet capillaries can lead to sudden signal dropouts or drifts of the signal intensity, particularly when materials of different conductivity are in contact with the capillary duct. Molecular layers of water and other gases such as liquid chromatography solvents always form on the surfaces of inlet capillaries at atmospheric pressure ionization conditions. These surface layers play a major role in ion transmission and the occurrence of charging effects, as ions adsorb on the capillary walls as well, charging the walls to electric potentials of up to kilovolts and eventually leading to a hindrance of ion transport into or through the capillary duct. In this work, surface charging effects are reported in dependence on the capillary material, i.e., borosilicate glass, (reduced) lead silicate, quartz, and metal. Low electrical conductance materials show a more pronounced long-term signal drift (e.g., quartz), while higher electrical conductance materials lead to stable long-term behavior.
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Affiliation(s)
- Valerie Derpmann
- Physical and Theoretical Chemistry, University of Wuppertal, Gausstrasse 20, 42119 Wuppertal, Germany
| | - David Müller
- Physical and Theoretical Chemistry, University of Wuppertal, Gausstrasse 20, 42119 Wuppertal, Germany
| | - Alexander Haack
- Physical and Theoretical Chemistry, University of Wuppertal, Gausstrasse 20, 42119 Wuppertal, Germany
| | - Walter Wissdorf
- Physical and Theoretical Chemistry, University of Wuppertal, Gausstrasse 20, 42119 Wuppertal, Germany
| | - Hendrik Kersten
- Physical and Theoretical Chemistry, University of Wuppertal, Gausstrasse 20, 42119 Wuppertal, Germany
| | - Thorsten Benter
- Physical and Theoretical Chemistry, University of Wuppertal, Gausstrasse 20, 42119 Wuppertal, Germany
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Gilbert-López B, Lara-Ortega FJ, Robles-Molina J, Brandt S, Schütz A, Moreno-González D, García-Reyes JF, Molina-Díaz A, Franzke J. Detection of multiclass explosives and related compounds in soil and water by liquid chromatography-dielectric barrier discharge ionization-mass spectrometry. Anal Bioanal Chem 2019; 411:4785-4796. [DOI: 10.1007/s00216-019-01627-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2018] [Revised: 01/10/2019] [Accepted: 01/15/2019] [Indexed: 10/27/2022]
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Rapid identification and desorption mechanisms of nitrogen-based explosives by ambient micro-fabricated glow discharge plasma desorption/ionization (MFGDP) mass spectrometry. Talanta 2017; 167:75-85. [DOI: 10.1016/j.talanta.2017.02.011] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2017] [Accepted: 02/04/2017] [Indexed: 01/22/2023]
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Wißdorf W, Müller D, Brachthäuser Y, Langner M, Derpmann V, Klopotowski S, Polaczek C, Kersten H, Brockmann K, Benter T. Gas Flow Dynamics in Inlet Capillaries: Evidence for non Laminar Conditions. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2016; 27:1550-1563. [PMID: 27245455 DOI: 10.1007/s13361-016-1415-z] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2016] [Revised: 04/09/2016] [Accepted: 04/19/2016] [Indexed: 06/05/2023]
Abstract
In this work, the characteristics of gas flow in inlet capillaries are examined. Such inlet capillaries are widely used as a first flow restriction stage in commercial atmospheric pressure ionization mass spectrometers. Contrary to the common assumption, we consider the gas flow in typical glass inlet capillaries with 0.5 to 0.6 mm inner diameters and lengths about 20 cm as transitional or turbulent. The measured volume flow of the choked turbulent gas stream in such capillaries is 0.8 L·min(-1) to 1.6 L·min(-1) under typical operation conditions, which is in good agreement to theoretically calculated values. Likewise, the change of the volume flow in dependence of the pressure difference along the capillary agrees well with a theoretical model for turbulent conditions as well as with exemplary measurements of the static pressure inside the capillary channel. However, the results for the volume flow of heated glass and metal inlet capillaries are neither in agreement with turbulent nor with laminar models. The velocity profile of the neutral gas in a quartz capillary with an inner diameter similar to commercial inlet capillaries was experimentally determined with spatially resolved ion transfer time measurements. The determined gas velocity profiles do not contradict the turbulent character of the flow. Finally, inducing disturbances of the gas flow by placing obstacles in the capillary channel is found to not change the flow characteristics significantly. In combination the findings suggest that laminar conditions inside inlet capillaries are not a valid primary explanation for the observed high ion transparency of inlet capillaries under common operation conditions. Graphical Abstract ᅟ.
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Affiliation(s)
- Walter Wißdorf
- Bergische Universitat Wuppertal, Gaußstraße 20, 42119, Wuppertal, Germany.
| | - David Müller
- Bergische Universitat Wuppertal, Gaußstraße 20, 42119, Wuppertal, Germany
| | | | - Markus Langner
- Bergische Universitat Wuppertal, Gaußstraße 20, 42119, Wuppertal, Germany
| | - Valerie Derpmann
- Bergische Universitat Wuppertal, Gaußstraße 20, 42119, Wuppertal, Germany
| | | | - Christine Polaczek
- Bergische Universitat Wuppertal, Gaußstraße 20, 42119, Wuppertal, Germany
| | - Hendrik Kersten
- Bergische Universitat Wuppertal, Gaußstraße 20, 42119, Wuppertal, Germany
| | - Klaus Brockmann
- Bergische Universitat Wuppertal, Gaußstraße 20, 42119, Wuppertal, Germany
| | - Thorsten Benter
- Bergische Universitat Wuppertal, Gaußstraße 20, 42119, Wuppertal, Germany
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Jjunju FPM, Maher S, Li A, Syed SU, Smith B, Heeren RMA, Taylor S, Cooks RG. Hand-held portable desorption atmospheric pressure chemical ionization ion source for in situ analysis of nitroaromatic explosives. Anal Chem 2015; 87:10047-55. [PMID: 26329926 DOI: 10.1021/acs.analchem.5b02684] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
A novel, lightweight (0.6 kg), solvent- and gas-cylinder-free, hand-held ion source based on desorption atmospheric pressure chemical ionization has been developed and deployed for the analysis of nitroaromatic explosives on surfaces in open air, offering portability for in-field analysis. A small, inexpensive, rechargeable lithium polymer battery was used to power the custom-designed circuitry within the device, which generates up to ±5 kV dc voltage to ignite a corona discharge plasma in air for up to 12 h of continuous operation, and allowing positive- and negative-ion mass spectrometry. The generated plasma is pneumatically transported to the surface to be interrogated by ambient air at a rate of 1-3.5 L/min, compressed using a small on-board diaphragm pump. The plasma source allows liquid or solid samples to be examined almost instantaneously without any sample preparation in the open environment. The advantages of low carrier gas and low power consumption (<6 W), as well as zero solvent usage, have aided in developing the field-ready, hand-held device for trigger-based, "near-real-time" sampling/ionization. Individual nitroaromatic explosives (such as 2,4,6-trinitrotoluene) can be easily detected in amounts as low as 5.8 pg with a linear dynamic range of at least 10 (10-100 pg), a relative standard deviation of ca. 7%, and an R(2) value of 0.9986. Direct detection of several nitroaromatic compounds in a complex mixture without prior sample preparation is demonstrated, and their identities are confirmed by tandem mass spectrometry fragmentation patterns.
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Affiliation(s)
- Fred P M Jjunju
- Department of Electrical Engineering and Electronics, University of Liverpool , Liverpool L69 3GJ, U.K.,Q-Technologies Ltd. , 100 Childwall Road, Liverpool L15 6UX, U.K
| | - Simon Maher
- Department of Electrical Engineering and Electronics, University of Liverpool , Liverpool L69 3GJ, U.K
| | - Anyin Li
- Chemistry Department, Purdue University , West Lafayette, Indiana 47907, United States
| | - Sarfaraz U Syed
- M4I, the Maastricht Multi Modal Molecular Imaging Institute, University of Maastricht , Universiteitssingel 50, 6229 ER Maastricht, The Netherlands
| | - Barry Smith
- Department of Electrical Engineering and Electronics, University of Liverpool , Liverpool L69 3GJ, U.K.,Q-Technologies Ltd. , 100 Childwall Road, Liverpool L15 6UX, U.K
| | - Ron M A Heeren
- M4I, the Maastricht Multi Modal Molecular Imaging Institute, University of Maastricht , Universiteitssingel 50, 6229 ER Maastricht, The Netherlands
| | - Stephen Taylor
- Department of Electrical Engineering and Electronics, University of Liverpool , Liverpool L69 3GJ, U.K.,Q-Technologies Ltd. , 100 Childwall Road, Liverpool L15 6UX, U.K
| | - R Graham Cooks
- Chemistry Department, Purdue University , West Lafayette, Indiana 47907, United States
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Klee S, Thinius M, Brockmann KJ, Benter T. Capillary atmospheric pressure chemical ionization using liquid point electrodes. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2014; 28:1591-1600. [PMID: 24895256 DOI: 10.1002/rcm.6944] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2014] [Revised: 04/16/2014] [Accepted: 04/17/2014] [Indexed: 06/03/2023]
Abstract
RATIONALE Atmospheric pressure chemical ionization (APCI) sources operated with point to plane DC discharges ('Coronas') frequently suffer from point electrode degradation and potentially lead to oxidation and/or fragmentation of the generated analyte ions. It is postulated that these adverse effects are caused by the interaction of these ions with the discharge chemistry as well as en route to the mass analyzer region. METHODS The corona discharge metal point electrode is replaced by the conically shaped liquid effluent evolving from a fused-silica capillary, which is analogous but not identical to the Taylor cone formation in electrospray ionization. The liquid consisting of either pure water or water containing 0.1 %V formic acid is fed via a nano-flow delivery stage at typical flow rates between 1-800 μL/h. The liquid flow is continuously replenishing the surface of the point electrode. The source is directly coupled to the inlet capillary of appropriate mass spectrometers, e.g., the Bruker Daltonics and Agilent varieties. RESULTS The actively pumped liquid flow is supplying a constant amount of the reagent gas (H2O) to the corona region in the 20 ppmV to 30 %V range, leading to controlled, very stable operation of the source. The typical light emission observed for corona discharges is in very close proximity to the aqueous surface. Analyte protonation is the dominating ionization pathway. The degree of primary analyte fragmentation is extremely low. CONCLUSIONS We have developed a novel atmospheric pressure chemical ionization source designed for the hyphenation of nano-flow liquid chromatography and gas chromatography with atmospheric pressure ionization mass spectrometry. The proposed reaction mechanism including the electrochemistry occurring in the source along with formation of protonated analyte molecules via collision-induced dissociation (CID) is in full accord with the experimental results. The system exhibits an extremely stable performance over prolonged operation times, sole generation of protonated molecules, and low degree of analyte ion fragmentation.
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Affiliation(s)
- Sonja Klee
- Institute for Pure and Applied Mass Spectrometry, Physical and Theoretical Chemistry, University of Wuppertal, Gauß Str. 20, 42119, Wuppertal, Germany
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