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Li HI, Prabhu GRD, Buchowiecki K, Urban PL. High-Speed Schlieren Imaging of Vapor Formation in Electrospray Plume. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2024; 35:244-254. [PMID: 38227955 DOI: 10.1021/jasms.3c00345] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2024]
Abstract
Previous mechanistic descriptions of electrosprays mostly focused on the dynamics of Taylor cones, initial droplets, and progeny droplets. However, vapor formation during droplet desolvation in an electrospray plume has not been discussed to a great extent. Here, we implement a double-pass on-axis schlieren high-speed imaging system to observe generation and propagation of vapors in an offline electrospray source under different conditions. Switching between turbulent and laminar vapor flow was observed for all of the scanned conditions, which may be attributed to randomly occurring disturbances in the sample flow inside the electrospray emitter. Calculation of mean vapor flow velocity and analysis of vapor flow patterns were performed using in-house developed image processing programs. Experiments performed at different electrospray voltages (0-6 kV), solvent flow rates (100-600 μL min-1), and methanol concentrations (50-100%), indicate only a weak dependency between electrospray voltage and mean vapor velocity, implying that the vapor is mostly neutral; thus, the vapor is not accelerated by electric field. On the other hand, electrospraying solutions of analytes (with mass 151 Da or 12 kDa) did not remarkably increase the overall vapor flow velocity. The source of vapor's velocity is attributed to the inertia of the electrospray droplets. Although there are some differences between a modern electrospray ionization (ESI) setup and the setup used in our experiment (e.g., using a higher flow rate and larger emitter), we believe the findings of our study can be projected to a modern ESI setup.
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Affiliation(s)
- Hou-I Li
- Department of Chemistry, National Tsing Hua University, 101, Section 2, Kuang-Fu Rd., Hsinchu 300044, Taiwan
| | - Gurpur Rakesh D Prabhu
- Department of Chemistry, National Tsing Hua University, 101, Section 2, Kuang-Fu Rd., Hsinchu 300044, Taiwan
| | - Krzysztof Buchowiecki
- Department of Chemistry, National Tsing Hua University, 101, Section 2, Kuang-Fu Rd., Hsinchu 300044, Taiwan
| | - Pawel L Urban
- Department of Chemistry, National Tsing Hua University, 101, Section 2, Kuang-Fu Rd., Hsinchu 300044, Taiwan
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2
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Gong X, Shi S, Zhang D, Gamez G. Quantitative Analysis of Exhaled Breath Collected on Filter Substrates via Low-Temperature Plasma Desorption/Ionization Mass Spectrometry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2022; 33:1518-1529. [PMID: 35792104 DOI: 10.1021/jasms.2c00109] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Breath analysis has attracted increasing attention in recent years due to its great potential for disease diagnostics at early stages and for clinical drug monitoring. There are several recent examples of successful development of real-time, in vivo quantitative analysis of exhaled breath metabolites via mass spectrometry. On the other hand, current mass spectrometer accessibility limitations restrict point-of-care applications. Here now, an offline method is developed for quantitative analysis of exhaled breath collected on inexpensive filter substrates for direct desorption and ionization by using low-temperature plasma-mass spectrometry (LTP-MS). In particular, different operating conditions of the ionization source were systematically studied to optimize desorption/ionization by using glycerol, a low volatility compound. Applications with respect to propofol, γ-valprolactone, and nicotine analysis in exhaled breath are demonstrated in this study. The effects of several filter substrate properties, including filter material and pore size, on the analyte signal were characterized. Cellulose filter papers performed best with the present analytes. In addition, filters with smaller pores enabled a more efficient sample collection. Furthermore, sample-collection flow rate was determined to have a very significant effect, with slower flow rates yielding the best results. It was also found that filters loaded with sample can be successfully stored in glass vials with no observable sample loss even after 3 days. Limits of detection under optimized conditions are shown to be competitive or significantly better compared with relevant techniques and with additional benefits of cost-efficiency and sample storage capabilities.
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Affiliation(s)
- Xiaoxia Gong
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409-1061, United States
| | - Songyue Shi
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409-1061, United States
| | - Dong Zhang
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409-1061, United States
| | - Gerardo Gamez
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409-1061, United States
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Latif M, Chen X, Gandhi VD, Larriba-Andaluz C, Gamez G. Field-Switching Repeller Flowing Atmospheric-Pressure Afterglow Drift Tube Ion Mobility Spectrometry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2022; 33:635-648. [PMID: 35235331 DOI: 10.1021/jasms.1c00309] [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] [Indexed: 06/14/2023]
Abstract
In this work, a field-switching (FS) technique is employed with a flowing atmospheric pressure afterglow (FAPA) source in drift tube ion mobility spectrometry (DTIMS). The premise is to incorporate a tip-repeller electrode as a substitute for the Bradbury-Nielsen gate (BNG) so as to overcome corresponding disadvantages of the BNG, including the gate depletion effect (GDE). The DTIMS spectra were optimized in terms of peak shape and full width by inserting an aperture at the DTIMS inlet that was used to control the neutral molecules' penetration into the separation region, thus preventing neutral-ion reactions inside. The FAPA and repeller's experimental operating conditions including drift and plasma gas flow rates, pulse injection times, repeller positioning and voltage, FAPA current, and effluent angle were optimized. Ion mobility spectra of selected compounds were captured, and the corresponding reduced mobility values were calculated and compared with the literature. The 6-fold improvements in limit of detection (LOD) compared with previous work were obtained for 2,6-DTBP and acetaminophen. The enhanced performance of the FS-FAPA-DTIMS was also investigated as a function of the GDE when compared with FAPA-DTIMS containing BNG.
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Affiliation(s)
- Mohsen Latif
- Department of Mechanical and Energy Engineering, Indiana University-Purdue University Indianapolis, Indianapolis, Indiana 46202, United States
- Mechanical Engineering, Purdue University, 610 Purdue Mall, West Lafayette, Indiana 47907, United States
| | - Xi Chen
- Department of Mechanical and Energy Engineering, Indiana University-Purdue University Indianapolis, Indianapolis, Indiana 46202, United States
- Mechanical Engineering, Purdue University, 610 Purdue Mall, West Lafayette, Indiana 47907, United States
| | - Viraj D Gandhi
- Department of Mechanical and Energy Engineering, Indiana University-Purdue University Indianapolis, Indianapolis, Indiana 46202, United States
- Mechanical Engineering, Purdue University, 610 Purdue Mall, West Lafayette, Indiana 47907, United States
| | - Carlos Larriba-Andaluz
- Department of Mechanical and Energy Engineering, Indiana University-Purdue University Indianapolis, Indianapolis, Indiana 46202, United States
| | - Gerardo Gamez
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409-1061, United States
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Oliva M, Zhang D, Prada-Tiedemann P, Gamez G. Laser assisted sampling vs direct desorption flowing atmospheric pressure afterglow mass spectrometry of complex polymer samples: Forensic implications for pressure sensitive tape chemical analysis. Talanta 2021; 231:122333. [PMID: 33965014 DOI: 10.1016/j.talanta.2021.122333] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Revised: 03/18/2021] [Accepted: 03/19/2021] [Indexed: 11/29/2022]
Abstract
Flowing atmospheric pressure afterglow (FAPA) mass spectrometry (MS) is an easy-to-use, cost-effective, and potentially portable technique that allows direct desorption/ionization from samples with little-to-no sample preparation for real-time chemical analysis. However, it has limitations regarding analytes with low desorption efficiency, such as polymers. Here, laser assisted sampling (LAS) is developed and coupled to FAPA MS to allow access to a wider range of chemical information from polymer samples. This is achieved through laser-induced pyrolysis conditions that provide a much higher degree of spatio-temporal control compared to typical pyrolysis techniques. LAS FAPA MS, together with direct desorption FAPA MS, is implemented on pressure sensitive adhesive (PSA) tape samples, which are often found at crime scenes and recovered as forensic evidence. Comparative PSA tape examination is typically performed to assess any differences in the comparison of unknown and known samples and provide an evidentiary association between suspects and crime scenes in forensic applications. PSA tape samples from several manufacturers of duct, masking, and electrical tape were analyzed from the adhesive and backing side. Direct desorption FAPA provides top-surface selectivity and the tape mass spectra are dominated by more peaks at lower m/z, many of which correspond to polymer additives. LAS gives access to sampling from all of the tape layers and the FAPA mass spectra is extended to higher m/z, while polymer fragmentation patterns are evident. Principal components analysis (PCA) was implemented to assess the ability of each technique to distinguish and categorize identified tape classes within the sampled population. The complementary nature of the resulting mass spectra from direct desorption vs LAS FAPA was evident from the PCA as different tape brands sub-sets were discriminated by each technique. The differentiation obtained by combining both methods is already competitive, or better, than conventional techniques, with the additional benefits of AMS.
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Affiliation(s)
- Maureen Oliva
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX, 79409-1061, USA; Department of Environmental Toxicology, Institute for Forensic Science, Texas Tech University, Lubbock, TX, 79414, USA
| | - Dong Zhang
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX, 79409-1061, USA
| | - Paola Prada-Tiedemann
- Department of Environmental Toxicology, Institute for Forensic Science, Texas Tech University, Lubbock, TX, 79414, USA
| | - Gerardo Gamez
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX, 79409-1061, USA.
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Latif M, Zhang D, Gamez G. Flowing atmospheric-pressure afterglow drift tube ion mobility spectrometry. Anal Chim Acta 2021; 1163:338507. [PMID: 34024423 DOI: 10.1016/j.aca.2021.338507] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2021] [Revised: 03/29/2021] [Accepted: 04/06/2021] [Indexed: 10/21/2022]
Abstract
In this work, the flowing atmospheric-pressure afterglow (FAPA) ambient desorption/ionization source has been coupled with stand-alone Drift Tube Ion Mobility Spectrometry (DTIMS) for the first time. A tip repeller electrode, modified to allow higher bias potential still below the Townsend's breakdown, was implemented at the FAPA/DTIMS interface to overcome the opposing potentials and facilitate ion transmission. The effect of the lab-built DTIMS and FAPA's operating conditions (such as plasma voltage, current, gas flow rate, repeller's potential and positioning, FAPA orientation, etc.) on the signal of selected analytes was studied, for both gas-phase injection and desorption. The FAPA reactant ion peak (RIP) reduced mobility coefficient (K0) corresponds to protonated water clusters (H2O)nH+. The FAPA-DTIMS spectra of several selected compounds showed that their K0 agrees with literature values. Moreover, quantitative characterization of acetaminophen and 2,6-di-tert-butylpyridine (2,6-DTBP) based on desorption or gas-phase injection yield limits of detection (LODs) of 0.03 μg and 18 ppb, respectively.
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Affiliation(s)
- Mohsen Latif
- Department of Chemistry and Biochemistry, Texas Tech University, TX, 79409-1061, Lubbock, USA
| | - Dong Zhang
- Department of Chemistry and Biochemistry, Texas Tech University, TX, 79409-1061, Lubbock, USA
| | - Gerardo Gamez
- Department of Chemistry and Biochemistry, Texas Tech University, TX, 79409-1061, Lubbock, USA.
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Kuhlmann C, Shelley JT, Engelhard C. Plasma-Based Ambient Desorption/Ionization Mass Spectrometry for the Analysis of Liquid Crystals Employed in Display Devices. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2019; 30:2101-2113. [PMID: 31385257 DOI: 10.1007/s13361-019-02280-w] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2019] [Revised: 06/27/2019] [Accepted: 06/28/2019] [Indexed: 06/10/2023]
Abstract
Liquid-crystal displays (LCDs) are the most frequently used display technology worldwide these days. Due to the rather complex manufacturing process and purity requirements for the chemicals used, quality control and display failure analysis are important analytical tasks. Currently, the state-of-the-art techniques (e.g., high-performance liquid chromatography (HPLC), gas chromatography (GC) coupled to mass spectrometry (MS), time-of-flight secondary ion mass spectrometry (TOF-SIMS), or high-resolution microscopy) are costly and time-consuming. Hence, a new pathway to precisely analyze liquid-crystalline materials and LCDs in their native state is reported. A new approach for direct analysis via plasma-based ambient desorption/ionization mass spectrometry (ADI-MS) offers an inexpensive and faster alternative. In this study, direct analysis in real time (DART), the low-temperature plasma (LTP) probe, and flowing atmospheric-pressure afterglow (FAPA) ADI sources coupled to high-resolution mass spectrometry (HR-MS) are compared based on their capabilities and performance for liquid-crystal analysis. These sources enable direct analyte desorption from a sample surface at ambient conditions and ionize the vaporized analyte molecules in a subsequent step. Primarily, the ionization capabilities of the three ADI sources are compared for individual liquid-crystal standards, mixtures of liquid crystals (LCs), and complex liquid crystal/additive mixtures applied in commercially available LCDs. Furthermore, direct surface analysis from a glass substrate is also performed with ADI-MS to compare their applicability to this type of sample matrix.
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Affiliation(s)
- Christopher Kuhlmann
- Department of Chemistry and Biology, University of Siegen, Adolf-Reichwein-Str. 2, 57076, Siegen, Germany
| | - Jacob T Shelley
- Department of Chemistry and Biochemistry, Kent State University, 1175 Risman Drive, Kent, OH, 44242, USA
- Department of Chemistry and Chemical Biology, Rensselaer Polytechnic Institute, 110 8th Street, Troy, NY, 12180, USA
| | - Carsten Engelhard
- Department of Chemistry and Biology, University of Siegen, Adolf-Reichwein-Str. 2, 57076, Siegen, Germany.
- Center for Micro- and Nanochemistry and Engineering, University of Siegen, Adolf-Reichwein-Str. 2, 57076, Siegen, Germany.
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Shelley JT, Badal SP, Engelhard C, Hayen H. Ambient desorption/ionization mass spectrometry: evolution from rapid qualitative screening to accurate quantification tool. Anal Bioanal Chem 2018; 410:4061-4076. [PMID: 29700557 DOI: 10.1007/s00216-018-1023-9] [Citation(s) in RCA: 48] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2017] [Revised: 03/02/2018] [Accepted: 03/13/2018] [Indexed: 11/24/2022]
Abstract
In this article, some recent trends and developments in ambient desorption/ionization mass spectrometry (ADI-MS) are reviewed, with a special focus on quantitative analyses with direct, open-air sampling. Accurate quantification with ADI-MS is still not routinely performed, but this aspect is considered of utmost importance for the advancement of the field. In fact, several research groups are devoted to the development of novel and optimized ADI-MS approaches. Some key trends include novel sample introduction strategies for improved reproducibility, tailored sample preparation protocols for removing the matrix and matrix effects, and multimode ionization sources. In addition, there is significant interest in quantitative mass spectrometry imaging. Graphical abstract Conceptual diagram of the ambient desorption/ionization mass spectrometry approach with different desorption/ionization probes.
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Affiliation(s)
- Jacob T Shelley
- Department of Chemistry and Chemical Biology, Rensselaer Polytechnic Institute, 110 8th Street, Troy, NY, 12180, USA.
| | - Sunil P Badal
- Department of Chemistry and Chemical Biology, Rensselaer Polytechnic Institute, 110 8th Street, Troy, NY, 12180, USA
| | - Carsten Engelhard
- Department of Chemistry and Biology, University of Siegen, Adolf-Reichwein-Straße 2, 57076, Siegen, Germany
| | - Heiko Hayen
- Institute of Inorganic and Analytical Chemistry, University of Münster, Corrensstr. 30, 48149, Münster, Germany.
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Storey AP, Zeiri OM, Ray SJ, Hieftje GM. Use of Interrupted Helium Flow in the Analysis of Vapor Samples with Flowing Atmospheric-Pressure Afterglow-Mass Spectrometry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2017; 28:263-269. [PMID: 27757823 DOI: 10.1007/s13361-016-1520-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2016] [Revised: 09/27/2016] [Accepted: 10/02/2016] [Indexed: 06/06/2023]
Abstract
The flowing atmospheric-pressure afterglow (FAPA) source was used for the mass-spectrometric analysis of vapor samples introduced between the source and mass spectrometer inlet. Through interrupted operation of the plasma-supporting helium flow, helium consumption is greatly reduced and dynamic gas behavior occurs that was characterized by schlieren imaging. Moreover, mass spectra acquired immediately after the onset of helium flow exhibit a signal spike before declining and ultimately reaching a steady level. This initial signal appears to be due to greater interaction of sample vapor with the afterglow of the source when helium flow resumes. In part, the initial spike in signal can be attributed to a pooling of analyte vapor in the absence of helium flow from the source. Time-resolved schlieren imaging of the helium flow during on and off cycles provided insight into gas-flow patterns between the FAPA source and the MS inlet that were correlated with mass-spectral data. Graphical Abstract ᅟ.
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Affiliation(s)
- Andrew P Storey
- Department of Chemistry, Indiana University, Bloomington, IN, 47405, USA
| | - Offer M Zeiri
- Department of Chemistry, Indiana University, Bloomington, IN, 47405, USA
- Nuclear Research Center Negev, Beer-Sheva, Israel
| | - Steven J Ray
- Department of Chemistry, Indiana University, Bloomington, IN, 47405, USA
- Department of Chemistry, University at Buffalo, The State University of New York, Buffalo, NY, 14260, USA
| | - Gary M Hieftje
- Department of Chemistry, Indiana University, Bloomington, IN, 47405, USA.
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Winter GT, Wilhide JA, LaCourse WR. Visualization of Ambient Mass Spectrometry with the Use of Schlieren Photography. J Vis Exp 2016. [PMID: 27404400 DOI: 10.3791/54195] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
This manuscript outlines how to visualize mass spectrometry ambient ionization sources using schlieren photography. In order to properly optimize the mass spectrometer, it is necessary to characterize and understand the physical principles of the source. Most commercial ambient ionization sources utilize jets of nitrogen, helium, or atmospheric air to facilitate the ionization of the analyte. As a consequence, schlieren photography can be used to visualize the gas streams by exploiting the differences in refractive index between the streams and ambient air for visualization in real time. The basic setup requires a camera, mirror, flashlight, and razor blade. When properly configured, a real time image of the source is observed by watching its reflection. This allows for insight into the mechanism of action in the source, and pathways to its optimization can be elucidated. Light is shed on an otherwise invisible situation.
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Affiliation(s)
- Gregory T Winter
- Department of Chemistry and Biochemistry, University of Maryland, Baltimore County
| | - Joshua A Wilhide
- Department of Chemistry and Biochemistry, University of Maryland, Baltimore County
| | - William R LaCourse
- Department of Chemistry and Biochemistry, University of Maryland, Baltimore County;
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Keelor JD, Farnsworth PB, L Weber A, Abbott-Lyon H, Fernández FM. Multimodal Vacuum-Assisted Plasma Ion (VaPI) Source with Transmission Mode and Laser Ablation Sampling Capabilities. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2016; 27:897-907. [PMID: 26883531 DOI: 10.1007/s13361-016-1354-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/18/2015] [Revised: 01/22/2016] [Accepted: 01/25/2016] [Indexed: 06/05/2023]
Abstract
We have developed a multimodal ion source design that can be configured on the fly for various analysis modes, designed for more efficient and reproducible sampling at the mass spectrometer atmospheric pressure (AP) interface in a number of different applications. This vacuum-assisted plasma ionization (VaPI) source features interchangeable transmission mode and laser ablation sampling geometries. Operating in both AC and DC power regimes with similar results, the ion source was optimized for parameters including helium flow rate and gas temperature using transmission mode to analyze volatile standards and drug tablets. Using laser ablation, matrix effects were studied, and the source was used to monitor the products of model prebiotic synthetic reactions.
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Affiliation(s)
- Joel D Keelor
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA, 30332, USA
| | - Paul B Farnsworth
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT, 84602, USA
| | | | - Heather Abbott-Lyon
- Department of Chemistry and Biochemistry, Kennesaw State University, Kennesaw, GA, 30144, USA
| | - Facundo M Fernández
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA, 30332, USA.
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Häbe TT, Morlock GE. Improved desorption/ionization and ion transmission in surface scanning by direct analysis in real time mass spectrometry. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2016; 30:321-332. [PMID: 26689161 DOI: 10.1002/rcm.7434] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2015] [Revised: 10/19/2015] [Accepted: 10/20/2015] [Indexed: 06/05/2023]
Abstract
RATIONALE Modifications to the Direct Analysis in Real Time mass spectrometry (DART-MS) interface, its source cap and transfer tube were necessary to obtain highest efficiency in desorption and ionization from the sampling surface and in ion transmission into the MS system. These issues are crucial for the trace analysis of any surface and the hyphenation of high-performance thin-layer chromatography (HPTLC) with DART-MS. METHODS The ion source mounting was modified to enable short source caps to be utilized in combination with a short transfer tube. The grid voltage contact section was readjusted to increase the intensity of the metastable gas stream towards the substrate. Eighteen different cap and two transfer tube geometries (including gas-stream focusing), along with the influence of their distance from the mass spectrometer glass capillary, were investigated for best signal intensity. RESULTS Using shortened source caps with staged inner bore, a transfer tube with gas-stream focusing and an optimized mounting geometry for DART-MS scanning along five identical deposited bands (600 ng each) of butyl 4-hydroxybenzoate, an average signal precision of 3.6% was obtained and the signal intensity was increased by a factor of 34. The width of the gas impact area did not exceed 1.5 mm and the smallest FWHM was determined to be 0.9 mm. CONCLUSIONS The desorption strength, ionization efficacy and ion transmission were improved significantly giving increased detectability using this further modified DART-MS interface with reduced cap length and optimum transfer tube geometry. The resolution was comparable with state-of-the-art densitometry. With this setup, reliable HPTLC surface scanning is possible, even for substance amounts in the low-nanogram range.
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Affiliation(s)
- Tim T Häbe
- Interdisciplinary Research Center (IFZ) and Institute of Nutritional Science, Chair of Food Science, Justus Liebig University Giessen, Heinrich-Buff-Ring 26-32, 35392, Giessen, Germany
| | - Gertrud E Morlock
- Interdisciplinary Research Center (IFZ) and Institute of Nutritional Science, Chair of Food Science, Justus Liebig University Giessen, Heinrich-Buff-Ring 26-32, 35392, Giessen, Germany
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Winter GT, Wilhide JA, LaCourse WR. Characterization of a Direct Sample Analysis (DSA) Ambient Ionization Source. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2015; 26:1502-1507. [PMID: 26091890 DOI: 10.1007/s13361-015-1175-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2014] [Revised: 04/21/2015] [Accepted: 04/25/2015] [Indexed: 06/04/2023]
Abstract
Water cluster ion intensity and distribution is affected by source conditions in direct sample analysis (DSA) ionization. Parameters investigated in this paper include source nozzle diameter, gas flow rate, and source positions relative to the mass spectrometer inlet. Schlieren photography was used to image the gas flow profile exiting the nozzle. Smaller nozzle diameters and higher flow rates produced clusters of the type [H + (H(2)O)(n)](+) with greater n and higher intensity than larger nozzles and lower gas flow rates. At high gas flow rates, the gas flow profile widened compared with the original nozzle diameter. At lower flow rates, the amount of expansion was reduced, which suggests that lowering the flow rate may allow for improvements in sampling spatial resolution.
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Affiliation(s)
- Gregory T Winter
- University of Maryland, Baltimore County, Baltimore, MD, 21250, USA
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13
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Chernetsova ES, Morlock GE. Aspects of surface scanning by direct analysis in real time mass spectrometry employing plasma glow visualization. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2015; 29:1242-1252. [PMID: 26395608 DOI: 10.1002/rcm.7221] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2015] [Revised: 04/29/2015] [Accepted: 04/30/2015] [Indexed: 06/05/2023]
Abstract
RATIONALE Visual monitoring of the Direct Analysis in Real Time (DART) gas impact region during sampling was demonstrated via its metastable plasma glow. It is known that adding neon into helium for DART leads to plasma glow, but this effect has not been used in practice and discussed in the literature so far. METHODS A single quadrupole mass spectrometer with a DART SVPA ion source was used for recording of DART mass spectra from different surfaces, using galangin and p-coumaric acid as model analytes. In specific cases, the composition of the mass spectra was clarified using an Orbitrap mass spectrometer. RESULTS Plasma glow visualization made it possible to track the metastable gas distributions during surface scanning. The influence on the composition of the mass spectra was studied for different carrier gases, i.e. pure helium versus a helium-neon mixture, and for the vacuum pumping rate. The spatial resolution was substantially improved via a DART cap with a narrowed internal diameter, but impaired by a decreased sensitivity. Comparably low signal intensities were obtained for analytes on porous layers due to analyte penetration and metastable gas scattering. CONCLUSIONS Visualization through the plasma glow enables the optimal selection of the coordinates for DART-MS analysis and thus it will support scanning and imaging MS on surfaces, including porous planar chromatographic separation materials.
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Affiliation(s)
- Elena S Chernetsova
- Institute of Nutritional Science, Chair of Food Science, Justus Liebig University Giessen, Interdisciplinary Research Center (IFZ), Heinrich-Buff-Ring 26-32, 35392, Giessen, Germany
- Institute of Food Chemistry, University of Hohenheim, Garbenstrasse 28, 70599, Stuttgart, Germany
| | - Gertrud E Morlock
- Institute of Nutritional Science, Chair of Food Science, Justus Liebig University Giessen, Interdisciplinary Research Center (IFZ), Heinrich-Buff-Ring 26-32, 35392, Giessen, Germany
- Institute of Food Chemistry, University of Hohenheim, Garbenstrasse 28, 70599, Stuttgart, Germany
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Curtis M, Keelor JD, Jones CM, Pittman JJ, Jones PR, Sparkman OD, Fernández FM. Schlieren visualization of fluid dynamics effects in direct analysis in real time mass spectrometry. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2015; 29:431-439. [PMID: 26349465 DOI: 10.1002/rcm.7119] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2014] [Revised: 12/05/2014] [Accepted: 12/06/2014] [Indexed: 06/05/2023]
Abstract
RATIONALE The success of ambient analysis using plasma-based ion sources depends heavily on fluid dynamics and mass transport efficiency in the sample region. To help characterize the influence of these determining factors, visualization of the gas flow profile for a Direct Analysis in Real Time (DART) ion source at the mass spectrometer atmospheric pressure (AP) interface was performed using the Schlieren technique. METHODS The DART helium flow pattern was imaged in model systems incorporating different interface designs, i.e. skimmer or capillary inlet, and for sampling strategies using several types of traditional DART sample probes including a glass capillary, swab, and drug tablet. Notably, Schlieren experiments were conducted on instruments equipped with the gas-ion separator tube (GIST) adapter and Vapur® pump, and on setups featuring the transmission mode (TM) DART module used in standard practice. RESULTS DART sources were seen to expel a collimated, highly laminar helium stream across interface distances up to ~8 cm. The helium stream was robust to the influence of gas temperature (50-500 °C) and flow rate (≤3.5 L min(-1) ), but considerable DART gas deflection or full disruption was observed in each sampling scenario. The severity of the flow disturbance depended on probe size and placement, the GIST/Vapur® settings, or counter-current gas movements present at the interface. CONCLUSIONS The real-time Schlieren visualizations introduced in this work provide new insight on the fluid dynamics within the DART-MS sample gap while also helping to identify those experimental parameters requiring optimization for improved transmission.
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Affiliation(s)
- Matthew Curtis
- Department of Chemistry, Pacific Mass Spectrometry Facility, University of the Pacific, Stockton, CA, 95211, USA
| | - Joel D Keelor
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA, 30332, USA
| | - Christina M Jones
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA, 30332, USA
| | - Jennifer J Pittman
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA, 30332, USA
| | - Patrick R Jones
- Department of Chemistry, Pacific Mass Spectrometry Facility, University of the Pacific, Stockton, CA, 95211, USA
| | - O David Sparkman
- Department of Chemistry, Pacific Mass Spectrometry Facility, University of the Pacific, Stockton, CA, 95211, USA
| | - Facundo M Fernández
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA, 30332, USA
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Pfeuffer KP, Caldwell J, Shelley JT, Ray SJ, Hieftje GM. Detection of counterfeit electronic components through ambient mass spectrometry and chemometrics. Analyst 2014; 139:4505-11. [DOI: 10.1039/c4an01071j] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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