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Bouza M, Ahmed E, Rocío-Bautista P, Brandt S, Franzke J, Molina-Díaz A, García-Reyes JF, Donald WA. Ion Heating in Advanced Dielectric Barrier Discharge Ion Sources for Ambient Mass Spectrometry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2023; 34:1145-1152. [PMID: 37231669 PMCID: PMC10251516 DOI: 10.1021/jasms.3c00087] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Revised: 05/10/2023] [Accepted: 05/12/2023] [Indexed: 05/27/2023]
Abstract
Dielectric barrier discharges (DBD) are highly versatile plasma sources for forming ions at atmospheric pressure and near ambient temperatures for the rapid, direct, and sensitive analysis of molecules by mass spectrometry (MS). Ambient ion sources should ideally form intact ions, as in-source fragmentation can limit sensitivity, increase spectral complexity, and hinder interpretation. Here, we report the measurement of ion internal energy distributions for the four primary classes of DBD-based ion sources, specifically DBD ionization (DBDI), low-temperature plasma (LTP), flexible microtube plasma (FμTP), and active capillary plasma ionization (ACaPI), in addition to atmospheric pressure chemical ionization (APCI) using para-substituted benzylammonium thermometer ions. Surprisingly, the average extent of energy deposited by the use of ACaPI (90.6 kJ mol-1) was ∼40 kJ mol-1 lower than the other ion sources (DBDI, LTP, FμTP, and APCI; 130.2 to 134.1 kJ mol-1) in their conventional configurations, and slightly higher than electrospray ionization (80.8 kJ mol-1). The internal energy distributions did not depend strongly on the sample introduction conditions (i.e., the use of different solvents and sample vaporization temperatures) or the DBD plasma conditions (i.e., maximum applied voltage). By positioning the DBDI, LTP, and FμTP plasma jets on axis with the capillary entrance to the mass spectrometer, the extent of internal energy deposition could be reduced by up to 20 kJ mol-1, although at the expense of sensitivity. Overall, the use of an active capillary-based DBD can result in substantially less fragmentation of ions with labile bonds than alternate DBD sources and APCI with comparably high sensitivity.
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Affiliation(s)
- Marcos Bouza
- Analytical
Chemistry Research Group, Department of Physical and Analytical Chemistry, University of Jaén, Campus Las Lagunillas, 23071 Jaén, Spain
| | - Ezaz Ahmed
- School
of Chemistry, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Priscilla Rocío-Bautista
- Analytical
Chemistry Research Group, Department of Physical and Analytical Chemistry, University of Jaén, Campus Las Lagunillas, 23071 Jaén, Spain
| | - Sebastian Brandt
- ISAS—Leibniz
Institut für Analytische Wissenschaften, Bunsen-Kirchhoff-Str. 11, 44139 Dortmund, Germany
| | - Joachim Franzke
- ISAS—Leibniz
Institut für Analytische Wissenschaften, Bunsen-Kirchhoff-Str. 11, 44139 Dortmund, Germany
| | - Antonio Molina-Díaz
- Analytical
Chemistry Research Group, Department of Physical and Analytical Chemistry, University of Jaén, Campus Las Lagunillas, 23071 Jaén, Spain
| | - Juan F. García-Reyes
- Analytical
Chemistry Research Group, Department of Physical and Analytical Chemistry, University of Jaén, Campus Las Lagunillas, 23071 Jaén, Spain
| | - William A. Donald
- School
of Chemistry, University of New South Wales, Sydney, New South Wales 2052, Australia
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2
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Foest D, Knodel A, Ahrends R, Coman C, Franzke J, Brandt S. Flexible Microtube Plasma for the Consecutive-Ionization of Cholesterol in Nano-Electrospray Mass Spectrometry. Anal Chem 2023. [PMID: 37220280 DOI: 10.1021/acs.analchem.2c04052] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Electrospray ionization mass spectrometry (ESI-MS) is an established method for the identification of biomarkers. By nano-ESI (nESI), the polar molecular fraction of complex biological samples can be successfully ionized. In contrast, the less-polar free cholesterol, which serves as an important biomarker for several human diseases, is barely accessible by nESI. Although, complex scan functions of modern high-resolution MS devices are able to increase the signal-to-noise ratio, they are limited by the ionization efficiency of the nESI. One possible method to increase the ionization efficiency is the derivatization with acetyl chloride, however interferences with cholesteryl esters must be considered, so chromatographic separation or complex scan functions may be required. A novel approach to increase the yield of cholesterol ions of the nESI could be the application of a second consecutive-ionization process. This publication presents the flexible microtube plasma (FμTP) as a consecutive-ionization source, which allows the determination of cholesterol in nESI-MS analysis. Focusing on the analytical performance, the nESI-FμTP approach increases the cholesterol signal yield in a complex liver extract by a factor of 49. The repeatability and long-term stability could be successfully evaluated. A linear dynamic range of 1.7 orders of magnitude, a minimum detectability of 5.46 mg/L, and a high accuracy (deviation, -8.1%) demonstrates the nESI-FμTP-MS as an excellent approach for a derivatization-free determination of cholesterol.
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Affiliation(s)
- Daniel Foest
- Miniaturisation, Leibniz-Institut für Analytische Wissenschaften─ISAS─e.V., Bunsen-Kirchhoff-Str. 11, 44139 Dortmund, Germany
| | - Alexander Knodel
- Miniaturisation, Leibniz-Institut für Analytische Wissenschaften─ISAS─e.V., Bunsen-Kirchhoff-Str. 11, 44139 Dortmund, Germany
| | - Robert Ahrends
- Department of Analytical Chemistry, University of Vienna, Währingstr. 38, A-1090 Vienna, Austria
| | - Cristina Coman
- Department of Analytical Chemistry, University of Vienna, Währingstr. 38, A-1090 Vienna, Austria
| | - Joachim Franzke
- Miniaturisation, Leibniz-Institut für Analytische Wissenschaften─ISAS─e.V., Bunsen-Kirchhoff-Str. 11, 44139 Dortmund, Germany
| | - Sebastian Brandt
- Miniaturisation, Leibniz-Institut für Analytische Wissenschaften─ISAS─e.V., Bunsen-Kirchhoff-Str. 11, 44139 Dortmund, Germany
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3
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Samokhvalov A, McCombs S. In Situ Time-Dependent Attenuated Total Reflection Fourier Transform Infrared (ATR FT-IR) Spectroscopy of a Powdered Specimen in a Controlled Atmosphere: Monitoring Sorption and Desorption of Water Vapor. APPLIED SPECTROSCOPY 2023; 77:308-319. [PMID: 36526443 DOI: 10.1177/00037028221148492] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Attenuated total reflection Fourier transform infrared (ATR FT-IR) spectroscopy is a powerful instrumental method of chemical analysis of solids and liquids. The majority of published studies by in situ ATR FT-IR spectroscopy describe analysis of homogeneous samples, such as liquid solutions under circulation, or films on the ATR crystal that react with the gas of interest. The in situ ATR FT-IR spectroscopic studies of specimens in physical shape of crystals or powder that react with a gas or vapor are rare. This work describes a modification of in situ time-dependent ATR FT-IR spectroscopy to allow monitoring heterogeneous reaction "solid-gas" of powder in controlled atmosphere and in the time domain. Also, we describe a new facile gas flow chamber attachment to ATR FT-IR spectrometer which allows creating controlled atmosphere surrounding the specimen on the ATR crystal. Additionally, the capabilities of the described in situ time-dependent ATR FT-IR spectroscopy experiment in controlled atmosphere are enhanced by the sensor for in situ time-dependent monitoring the relative humidity (RH) of air surrounding the specimen. The operation of the setup for in situ time-dependent ATR FT-IR spectroscopy in controlled atmosphere is demonstrated by monitoring reaction of gradual desorption of water vapor from color-indicating molecular sieves under controlled low air humidity. Further, the described spectroscopic method and apparatus is applied to monitor the reverse process, namely sorption of water vapor by color-indicating molecular sieves under controlled elevated air humidity. Water molecules are found to reversibly interact with two distinct sorption sites in the sorbent: the Si-O backbone and the color-indicating Co(II) centers. The reported variant of in situ time-dependent ATR FT-IR spectroscopy in controlled atmosphere is powerful, yet facile and straightforward. It is promising for mechanistic, in situ studies of sorption, desorption, chemosensing, heterogeneous catalysis and photocatalysis, and analysis of chemical kinetics of various "solid-gas" reactions.
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Affiliation(s)
| | - Stanley McCombs
- Department of Physics & Engineering Physics, 1491Morgan State University, Baltimore, MD, USA
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4
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Bouza M, García-Martínez J, Gilbert-López B, Brandt S, García-Reyes JF, Molina-Díaz A, Franzke J. Dielectric Barrier Discharge Ionization Mechanisms: Polycyclic Aromatic Hydrocarbons as a Case of Study. Anal Chem 2023; 95:854-861. [PMID: 36538370 PMCID: PMC9850405 DOI: 10.1021/acs.analchem.2c03279] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2022] [Accepted: 12/13/2022] [Indexed: 12/24/2022]
Abstract
Dielectric barrier discharge ionization (DBDI) is a versatile tool for small-molecule mass spectrometry applications, helping cover from polar to low polar molecules. However, the plasma gas-phase interactions are highly complex and have been scarcely investigated. The ionization mechanisms of plasmas have long been assumed to be somewhat similar to atmospheric pressure chemical ionization (APCI). Here, we evaluated the ionization mechanisms of a two-ring DBDI ion source, using different discharge gases to analyze vaporized liquid samples. Polycyclic aromatic hydrocarbons (PAHs) were used as model analytes to assess the mechanisms' dominance: protonation, [M + H]+, or radical ion species formation, [M]·+. In the present work, two different ionization trends were observed for APCI and DBDI during the PAH analysis; the compounds with proton affinities (PA) over 856 kJ/mol were detected as [M + H]+ when APCI was used as ionization source. Meanwhile, independently of the PA, DBDI showed the prevalence of charge exchange reactions. The addition of dopants in the gas-phase region shifted the ionization mechanisms toward charge exchange reactions, facilitating the formation of [M]·+ ion species, showing anisole a significant boost of the PAH radical ion species signals, over nine times for Ar-Prop-DBDI analysis. The presence of high-energy metastable atoms (e.g., HeM) with high ionization potentials (IE = 19.80 eV) did not show boosted PAH abundances or extensive molecule fragmentation. Moreover, other species in the plasma jet region with closer and more appropriate IE, such as N2 B3Πg excited molecules, are likely responsible for PAH Penning ionization.
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Affiliation(s)
- Marcos Bouza
- Analytical
Chemistry Research Group, Department of Physical and Analytical Chemistry, University of Jaén, Campus Las Lagunillas, 23071Jaén, Spain
| | - Julio García-Martínez
- Analytical
Chemistry Research Group, Department of Physical and Analytical Chemistry, University of Jaén, Campus Las Lagunillas, 23071Jaén, Spain
| | - Bienvenida Gilbert-López
- Analytical
Chemistry Research Group, Department of Physical and Analytical Chemistry, University of Jaén, Campus Las Lagunillas, 23071Jaén, Spain
| | - Sebastian Brandt
- ISAS—Leibniz
Institut für Analytische Wissenschaften, Bunsen-Kirchhoff-Str. 11, 44139Dortmund, Germany
| | - Juan F. García-Reyes
- Analytical
Chemistry Research Group, Department of Physical and Analytical Chemistry, University of Jaén, Campus Las Lagunillas, 23071Jaén, Spain
| | - Antonio Molina-Díaz
- Analytical
Chemistry Research Group, Department of Physical and Analytical Chemistry, University of Jaén, Campus Las Lagunillas, 23071Jaén, Spain
| | - Joachim Franzke
- ISAS—Leibniz
Institut für Analytische Wissenschaften, Bunsen-Kirchhoff-Str. 11, 44139Dortmund, Germany
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5
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Yue H, He F, Zhao Z, Duan Y. Plasma-based ambient mass spectrometry: Recent progress and applications. MASS SPECTROMETRY REVIEWS 2023; 42:95-130. [PMID: 34128567 DOI: 10.1002/mas.21712] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2021] [Revised: 05/28/2020] [Accepted: 06/02/2020] [Indexed: 06/12/2023]
Abstract
Ambient mass spectrometry (AMS) has grown as a group of advanced analytical techniques that allow for the direct sampling and ionization of the analytes in different statuses from their native environment without or with minimum sample pretreatments. As a significant category of AMS, plasma-based AMS has gained a lot of attention due to its features that allow rapid, real-time, high-throughput, in vivo, and in situ analysis in various fields, including bioanalysis, pharmaceuticals, forensics, food safety, and mass spectrometry imaging. Tens of new methods have been developed since the introduction of the first plasma-based AMS technique direct analysis in real-time. This review first provides a comprehensive overview of the established plasma-based AMS techniques from their ion source configurations, mechanisms, and developments. Then, the progress of the representative applications in various scientific fields in the past 4 years (January 2017 to January 2021) has been summarized. Finally, we discuss the current challenges and propose the future directions of plasma-based AMS from our perspective.
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Affiliation(s)
- Hanlu Yue
- College of Life Sciences, Sichuan University, Chengdu, China
| | - Feiyao He
- College of Life Sciences, Sichuan University, Chengdu, China
| | - Zhongjun Zhao
- School of Chemical Engineering, Sichuan University, Chengdu, China
| | - Yixiang Duan
- College of Life Sciences, Sichuan University, Chengdu, China
- School of Manufacturing Science and Engineering, Sichuan University, Chengdu, China
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6
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Guo X, Pu J, Dai J, Zhao Z, Duan Y. Elucidation of formation mechanism responsible for charge-transfer reagent ions in microwave induced plasma desorption ionization (MIPDI) source. Talanta 2022; 250:123656. [DOI: 10.1016/j.talanta.2022.123656] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Revised: 05/30/2022] [Accepted: 06/03/2022] [Indexed: 11/29/2022]
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Ionization of semi-fluorinated n-alkanes in controlled atmosphere using flexible micro-tube plasma (FμTP) ionization source with square- and sine-wave voltage. Talanta 2022; 249:123662. [PMID: 35691129 DOI: 10.1016/j.talanta.2022.123662] [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: 02/07/2022] [Revised: 05/10/2022] [Accepted: 06/04/2022] [Indexed: 11/21/2022]
Abstract
Non-thermal plasma-based ionization sources have been widely used and shown excellent soft ionization performance in mass spectrometry. Despite their extensive application, the ionization mechanisms of these sources are of great interest for further exploring their full potential. A controlled atmosphere can provide a clean and controllable ionization environment and is beneficial for studying the ionization mechanism. The plasma source itself also has a significant impact on the ionization mechanism of the analyte, and the voltage waveform is one of the key parameters for controlling the plasma source. In this paper, a miniature flexible micro-tube plasma (FμTP) ionization source was sustained using both square and sine-wave voltage. The ionization processes of typical semi-fluorinated n-alkanes (SFAs) were investigated in the controlled atmosphere filled with 80% N2 and 20% O2. The main mass peaks using both square and sine-wave voltages are found to be [M-mH]+ and [M-mH+nO]+ (m = 1, 3; n = 0, 1, 2). However, for the square-wave voltage, the [M-H+O]+ species are the most abundant while [M-H]+ species are dominant for the sine-wave voltage, showing that the plasma generated with sine-wave voltage is somewhat "softer" than the one with square-wave voltage for SFAs. With the assistance of optical spectroscopy, the plasma developments in one discharge cycle for both voltage waveforms were obtained. Only one discharge can be found in each half cycle for square-wave voltage while several for the sine-wave voltage. These would be responsible for the different ionization behaviors in these two cases. This work provides more insight into the ionization mechanism of SFAs and more understanding of plasma-based soft ionization. In addition, the analytical performance was evaluated to be comparable when using these two voltage generators with a big difference in cost, which will benefit the instrumental development.
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8
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Foest D, Knodel A, Brandt S, Franzke J. Coupling paper spray ionization with the flexible microtube plasma for the determination of low polar biomarkers in mass spectrometry. Anal Chim Acta 2022; 1201:339619. [DOI: 10.1016/j.aca.2022.339619] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2021] [Revised: 01/21/2022] [Accepted: 02/14/2022] [Indexed: 11/15/2022]
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9
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Brecht D, Uteschil F, Schmitz OJ. Development of an inverse low-temperature plasma ionization source for liquid chromatography/mass spectrometry. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2021; 35:e9071. [PMID: 33625792 DOI: 10.1002/rcm.9071] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2020] [Revised: 02/17/2021] [Accepted: 02/19/2021] [Indexed: 06/12/2023]
Abstract
RATIONALE An argon inverse low-temperature plasma (iLTP) ionization source for liquid chromatography/tandem mass spectrometry was developed. The iLTP is constructed from simple chromatographic supply materials and is implemented into an atmospheric pressure chemical ionization (APCI) source replacing the APCI discharge needle electrode. The newly developed ion source was coupled to an ultra-high-performance liquid chromatography (UHPLC) system. METHODS The argon iLTP was characterized by optical emission spectroscopy. The soft ionization of selected standards was also demonstrated by direct infusion experiments. In addition to the use of argon as the discharge gas, helium, synthetic air, and oxygen were used, which were tested for their performance using testosterone and vitamin D3 . RESULTS Spectroscopic measurements of the argon plasma were conducted, demonstrating the main emission band of argon metastables with corresponding energies of 11.53 eV and 11.72 eV. Infusion experiments indicate a gentle ionization by iLTP, e.g. caffeine, testosterone, reserpine, vitamin D3 , and 25-hydroxyvitamin D3 , which resulted in the corresponding protonated molecules. The splitless coupling with UHPLC (possible flow rates >1000 μL min-1 ) shows promising results in interday repeatability (n = 10) for the substances with a relative standard deviation of less than 5% and limits of detection for caffeine, testosterone, reserpine, vitamin D3 , and 25-hydroxyvitamin D3 of 10 ng L-1 , 50 ng L-1 , 500 ng L-1 , 5 μg L-1 , and 5 μg L-1 , respectively. CONCLUSIONS The argon iLTP ion source presented in this work shows promising approaches in the field of ionization of small organic molecules. The mechanism related to the discharge gas argon has not been elucidated so far and further investigations are needed. The iLTP ion source shows a very good performance with UHPLC coupling, even at increased flow rates. It could be shown that an argon iLTP can compete with the helium dielectric barrier discharge (DBD) preferred in the literature, making it a more economical choice.
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Affiliation(s)
- Dominik Brecht
- Department of Applied Analytical Chemistry, University of Duisburg-Essen, Universitaetsstrasse 5, Essen, 45141, Germany
| | - Florian Uteschil
- Department of Applied Analytical Chemistry, University of Duisburg-Essen, Universitaetsstrasse 5, Essen, 45141, Germany
| | - Oliver J Schmitz
- Department of Applied Analytical Chemistry, University of Duisburg-Essen, Universitaetsstrasse 5, Essen, 45141, Germany
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10
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Vogel P, Lazarou C, Gazeli O, Brandt S, Franzke J, Moreno-González D. Study of Controlled Atmosphere Flexible Microtube Plasma Soft Ionization Mass Spectrometry for Detection of Volatile Organic Compounds as Potential Biomarkers in Saliva for Cancer. Anal Chem 2020; 92:9722-9729. [PMID: 32579344 DOI: 10.1021/acs.analchem.0c01063] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
A new soft ionization device for mass spectrometry is presented using the flexible microtube plasma under controlled atmospheric conditions. The controlled atmosphere flexible microtube plasma consists of the plasma source itself connected to a gas chromatograph and a mass spectrometer using a borosilicate glass cross piece. Controlled atmosphere, for example, nitrogen and/or an oxygen mixture, is introduced to the system to create a clean ionization environment. Reproducibility issues are discussed, and solutions are presented manipulating the gas flow in the cross piece. A proof of concept is shown using a ketone mixture introduced to the mass spectrometer to optimize atmospheric conditions. Furthermore, application of the presented device for the sensitive and nonfragmenting ionization of volatile organic biomarkers relevant for cancer is carried out. Sample treatment for human saliva is described, and relevant candidate biomarkers are measured in the saliva matrix, showing a very good ionization efficiency and neglectable matrix effects with limits of detection below 80 ppt.
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Affiliation(s)
- Pascal Vogel
- ISAS-Leibniz-Institut für Analytische Wissenschaften, Bunsen Kirchhoff Strasse 11, Dortmund 44139, Germany
| | - Constantinos Lazarou
- FOSS Research Centre for Sustainable Energy, PV Technology, University of Cyprus, 75 Kallipoleos Street, Nicosia 1678, Cyprus
| | - Odhisea Gazeli
- FOSS Research Centre for Sustainable Energy, PV Technology, University of Cyprus, 75 Kallipoleos Street, Nicosia 1678, Cyprus
| | - Sebastian Brandt
- ISAS-Leibniz-Institut für Analytische Wissenschaften, Bunsen Kirchhoff Strasse 11, Dortmund 44139, Germany
| | - Joachim Franzke
- ISAS-Leibniz-Institut für Analytische Wissenschaften, Bunsen Kirchhoff Strasse 11, Dortmund 44139, Germany
| | - David Moreno-González
- ISAS-Leibniz-Institut für Analytische Wissenschaften, Bunsen Kirchhoff Strasse 11, Dortmund 44139, Germany
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11
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Zheng K, Lesniewski JE, Dolan MJ, Li W, Metallo TT, Jorabchi K. Elemental Fluorine Detection by Dielectric Barrier Discharge Coupled to Nanoelectrospray Ionization Mass Spectrometry for Nontargeted Analysis of Fluorinated Compounds. Anal Chem 2020; 92:10129-10137. [PMID: 32578420 DOI: 10.1021/acs.analchem.0c02141] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The growing use of fluorochemicals has elevated the need for nontargeted detection of unknown fluorinated compounds and transformation products. Elemental mass spectrometry (MS) coupled to chromatography offers a facile approach for such analyses by using fluorine as an elemental tag. However, efficient ionization of fluorine has been an ongoing challenge. Here, we demonstrate a novel atmospheric-pressure elemental ionization method where fluorinated compounds separated by gas chromatography (GC) are converted to Na2F+ for nontargeted detection. The compounds are first introduced into a helium dielectric barrier discharge (DBD) for breakdown. The plasma products are subsequently ionized by interaction with a nanoelectrospray ionization (nano-ESI) plume of sodium-containing aqueous electrolytes. Our studies point to HF as the main plasma product contributing to Na2F+ formation. Moreover, the results reveal that Na2F+ is largely formed by the ion-neutral reaction between HF and Na2A(NaA)n+, gas-phase reagent ions produced by nano-ESI where A represents the anion of the electrolyte. Near-uniform fluorine response factors are obtained for a wide range of compounds, highlighting good efficiency of HF formation by DBD regardless of the chemical structure of the compounds. Detection limits of 3.5-19.4 pg of fluorine on-column are obtained using the reported GC-DBD-nano-ESI-MS. As an example of nontargeted screening, extractions from oil-and-water-repellent fabrics are analyzed via monitoring Na2F+, resulting in detection of a fluorinated compound on a clothing item. Notably, facile switching of the ion source to atmospheric-pressure chemical ionization with the exact same chromatographic method allows identification of the detected compound at the flagged retention time.
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Affiliation(s)
- Kunyu Zheng
- Department of Chemistry, Georgetown University, Washington, DC 20057, United States
| | - Joseph E Lesniewski
- Department of Chemistry, Georgetown University, Washington, DC 20057, United States
| | - Michael J Dolan
- Department of Chemistry, Georgetown University, Washington, DC 20057, United States
| | - Wanqing Li
- Department of Chemistry, Georgetown University, Washington, DC 20057, United States
| | - Tyler T Metallo
- Department of Chemistry, Georgetown University, Washington, DC 20057, United States
| | - Kaveh Jorabchi
- Department of Chemistry, Georgetown University, Washington, DC 20057, United States
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12
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Pu J, Dai J, He F, Zhu S, Zhao Z, Duan Y. Interpretation of Ionization Mechanism Responsible for Reagent Ion and Analyte Formation in Microwave-Induced Plasma Desorption Ionization Mass Spectrometry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2020; 31:752-762. [PMID: 32003981 DOI: 10.1021/jasms.0c00027] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Ambient desorption/ionization (ADI) sources coupled to mass spectrometer have gained increasing interest in the field of analytical chemistry for its fast and direct analysis of samples. Among many ADI sources, plasma-based ADI sources are an important branch. Despite its extensive use in mass spectrometry analysis, the ionization mechanism of these sources still remain uncertain. The study on ionization mechanism is of great significance to optimize the design of ion sources and to improve ionization efficiency. In this study, targeted research on a better understanding of afterglow distance effects on ionization process was conducted. Based on the quantified signal expression of reagent ions in mass spectrum, the concept that optimal atmospheric analysis distance of plasma ADI source is defined for the first time. From the perspective of mutual restriction effect between atmospheric components, the formation progress of reagent ions was visually revealed in detail, which involved the initial step of forming precursor reagent ions, the clusters reaction for increasing production of reagent ions, and the matrix effect results in reagent ion depletion. The formation mechanism of reagent ions further clarified the explicit reason for abundant reagent ions generated at an optimal distance. Most importantly, the analyte analysis results verified the significant impact of appropriate distance on ionization efficiency in afterglow region. It was confirmed that the quantity and type of reagent ions intimately influenced the status of analyte ions in mass spectrum.
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Affiliation(s)
| | - Jianxiong Dai
- College of Chemistry and Material Science, Northwest University, Xi'an 710069, P.R. China
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