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Trimpin S, Inutan ED, Pagnotti VS, Karki S, Marshall DD, Hoang K, Wang B, Lietz CB, Richards AL, Yenchick FS, Lee C, Lu IC, Fenner M, Madarshahian S, Saylor S, Chubatyi ND, Zimmerman T, Moreno-Pedraza A, Wang T, Adeniji-Adele A, Meher AK, Madagedara H, Owczarzak Z, Musavi A, Hendrickson TL, Peacock PM, Tomsho JW, Larsen BS, Prokai L, Shulaev V, Pophristic M, McEwen CN. Direct sub-atmospheric pressure ionization mass spectrometry: Evaporation/sublimation-driven ionization is amazing, fundamentally, and practically. JOURNAL OF MASS SPECTROMETRY : JMS 2024; 59:e5018. [PMID: 38736378 DOI: 10.1002/jms.5018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/18/2023] [Revised: 12/08/2023] [Accepted: 03/04/2024] [Indexed: 05/14/2024]
Abstract
This paper covers direct sub-atmospheric pressure ionization mass spectrometry (MS). The discovery, applications, and mechanistic aspects of novel ionization processes for use in MS that are not based on the high-energy input from voltage, laser, and/or high temperature but on sublimation/evaporation within a region linking a higher to lower pressure and modulated by heat and collisions, are discussed, including how this new reality has guided a series of discoveries, instrument developments, and commercialization. A research focus, inter alia, is on how best to understand, improve, and use these novel ionization processes, which convert volatile and nonvolatile compounds from solids (sublimation) or liquids (evaporation) into gas-phase ions for analysis by MS providing reproducible, accurate, sensitive, and prompt results. Our perception on how these unprecedented versus traditional ionization processes/methods relate to each other, how they can be made to coexist on the same mass spectrometer, and an outlook on new and expanded applications (e.g., clinical, portable, fast, safe, and autonomous) is presented, and is based on ST's Opening lecture presentation at the Nordic Mass spectrometry Conference, Geilo, Norway, January 2023. Focus will be on matrix-assisted ionization (MAI) and solvent-assisted ionization (SAI) MS covering the period from 2010 to 2023; a potential paradigm shift in the making.
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Affiliation(s)
- Sarah Trimpin
- Department of Chemistry, Wayne State University, Detroit, Michigan, USA
- MSTM, LLC, Newark, Delaware, USA
| | - Ellen D Inutan
- Department of Chemistry, Wayne State University, Detroit, Michigan, USA
- MSTM, LLC, Newark, Delaware, USA
- Mindanao State University-Iligan Institute of Technology, Iligan City, Philippines
| | - Vincent S Pagnotti
- Department of Chemistry & Biochemistry, Saint Joseph's University, Philadelphia, Pennsylvania, USA
| | - Santosh Karki
- Department of Chemistry, Wayne State University, Detroit, Michigan, USA
- MSTM, LLC, Newark, Delaware, USA
| | - Darrell D Marshall
- Department of Chemistry, Wayne State University, Detroit, Michigan, USA
- MSTM, LLC, Newark, Delaware, USA
| | - Khoa Hoang
- MSTM, LLC, Newark, Delaware, USA
- Department of Chemistry & Biochemistry, Saint Joseph's University, Philadelphia, Pennsylvania, USA
| | - Beixi Wang
- Department of Chemistry, Wayne State University, Detroit, Michigan, USA
| | | | - Alicia L Richards
- Department of Chemistry, Wayne State University, Detroit, Michigan, USA
| | - Frank S Yenchick
- Department of Chemistry, Wayne State University, Detroit, Michigan, USA
| | - Chuping Lee
- Department of Chemistry, Wayne State University, Detroit, Michigan, USA
| | - I-Chung Lu
- Department of Chemistry, Wayne State University, Detroit, Michigan, USA
- Department of Chemistry, National Chung Hsing University, Taichung, Taiwan
| | - Madeleine Fenner
- Department of Chemistry & Biochemistry, Saint Joseph's University, Philadelphia, Pennsylvania, USA
| | - Sara Madarshahian
- Department of Chemistry & Biochemistry, Saint Joseph's University, Philadelphia, Pennsylvania, USA
| | - Sarah Saylor
- Department of Chemistry & Biochemistry, Saint Joseph's University, Philadelphia, Pennsylvania, USA
| | - Nicolas D Chubatyi
- Department of Chemistry & Biochemistry, Saint Joseph's University, Philadelphia, Pennsylvania, USA
| | - Teresa Zimmerman
- Department of Chemistry, Wayne State University, Detroit, Michigan, USA
| | | | - Tongwen Wang
- Department of Chemistry & Biochemistry, Saint Joseph's University, Philadelphia, Pennsylvania, USA
| | - Adetoun Adeniji-Adele
- Department of Chemistry & Biochemistry, Saint Joseph's University, Philadelphia, Pennsylvania, USA
| | - Anil K Meher
- Department of Chemistry, Wayne State University, Detroit, Michigan, USA
- MSTM, LLC, Newark, Delaware, USA
| | - Hasini Madagedara
- Department of Chemistry, Wayne State University, Detroit, Michigan, USA
| | - Zachary Owczarzak
- Department of Chemistry, Wayne State University, Detroit, Michigan, USA
| | - Ahmed Musavi
- Department of Chemistry, Wayne State University, Detroit, Michigan, USA
| | | | | | - John W Tomsho
- Department of Chemistry & Biochemistry, Saint Joseph's University, Philadelphia, Pennsylvania, USA
| | | | - Laszlo Prokai
- Department of Pharmacology and Neuroscience, The University of North Texas Health Science Center at Forth Worth, Fort Worth, Texas, USA
| | - Vladimir Shulaev
- Department of Biological Sciences, The University of North Texas, Denton, Texas, USA
| | - Milan Pophristic
- MSTM, LLC, Newark, Delaware, USA
- Department of Chemistry & Biochemistry, Saint Joseph's University, Philadelphia, Pennsylvania, USA
| | - Charles N McEwen
- MSTM, LLC, Newark, Delaware, USA
- Department of Chemistry & Biochemistry, Saint Joseph's University, Philadelphia, Pennsylvania, USA
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Klöppner L, Harps LC, Parr MK. Sample Preparation Techniques for Growth-Promoting Agents in Various Mammalian Specimen Preceding MS-Analytics. Molecules 2024; 29:330. [PMID: 38257243 PMCID: PMC10818438 DOI: 10.3390/molecules29020330] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2023] [Revised: 12/24/2023] [Accepted: 01/01/2024] [Indexed: 01/24/2024] Open
Abstract
The misuse of growth-promoting drugs such as beta-2 agonists and steroids is a known problem in farming and sports competitions. Prior to the analysis of biological samples via liquid chromatography (LC)-mass spectrometry (MS) or gas chromatography (GC)-MS, sufficient sample preparation is required to reliably identify or determine the residues of drugs. In practice, broad screening methods are often used to save time and analyze as many compounds as possible. This review was conceptualized to analyze the literature from 2018 until October 2023 for sample preparation procedures applied to animal specimens before LC- or GC-MS analysis. The animals were either used in farming or sports. In the present review, solid phase extraction (SPE) was observed as the dominant sample clean-up technique for beta-2 agonists and steroids, followed by protein precipitation. For the extraction of beta-2 agonists, mixed-mode cation exchanger-based SPE phases were preferably applied, while for the steroids, various types of SPE materials were reported. Furthermore, dispersive SPE-based QuEChERs were utilized. Combinatory use of SPE and liquid-liquid extraction (LLE) was observed to cover further drug classes in addition to beta-2 agonists in broader screening methods.
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Affiliation(s)
| | | | - Maria Kristina Parr
- Institute of Pharmacy, Freie Universität Berlin, Königin-Luise-Straße 2+4, 14195 Berlin, Germany; (L.K.); (L.C.H.)
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Trimpin S, Inutan E, Coffinberger H, Hoang K, Yenchick F, Wager-Miller J, Pophristic M, Mackie K, McEwen CN. Instrumentation development, improvement, simplification, and miniaturization: The multifunctional plate source for use in mass spectrometry. EUROPEAN JOURNAL OF MASS SPECTROMETRY (CHICHESTER, ENGLAND) 2023; 29:276-291. [PMID: 37999746 DOI: 10.1177/14690667231211486] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2023]
Abstract
In remembrance of Prof. Dr Przybylski, we are presenting a vision towards his beloved mass spectrometry (MS) and its far-reaching promises outside of the academic laboratory. Sub-atmospheric pressure (AP) ionization MS is well positioned to make a step-change in direct ionization, a concept that allows sublimation/evaporation ionization and mass analyses of volatile and nonvolatile molecules from clean or dirty samples, directly, accurately, sensitively, and in a straightforward manner that has the potential to expand the field of MS into unchartered application areas. Contrary to ambient ionization MS, ionization commences in the sub-AP region of the mass spectrometer, important for practical and safety reasons, and offers inter alia, simplicity, speed, sensitivity, and robustness directly from real-world samples without cleanup. The plate source concept, presented here, provides an easy to use, rapid, and direct sample introduction from AP into the sub-AP of a mass spectrometer. Utilizing sub-AP ionization MS based on the plate source concept, small to large molecules from various environments that would be deemed too dirty for some direct MS methods are demonstrated. The new source concept can be expanded to include multiple ionization methods using the same plate source "front end" without the need to vent the mass spectrometer between the different methods, thus allowing ionization of more compounds on the same mass spectrometer for which any one ionization method may be insufficient. Examples such as fentanyl, gamma-hydroxybutyric acid, clozapine, 1-propionyllysergic acid, hydrocodone angiotensin I and II, myoglobin, and carbonic anhydrase are included.
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Affiliation(s)
- Sarah Trimpin
- Wayne State University, Detroit, MI, USA
- Research and Development, MSTM, LLC, Philadelphia, PA, USA
| | - Ellen Inutan
- Department of Chemistry, Mindanao State University-Illigan Institute of Technology, Illigan City, Philippines
| | - Hope Coffinberger
- Research and Development, MSTM, LLC, Philadelphia, PA, USA
- Department of Chemistry & Biochemistry, Saint Joseph's University, Philadelphia, PA, USA
| | - Khoa Hoang
- Research and Development, MSTM, LLC, Philadelphia, PA, USA
- Department of Chemistry & Biochemistry, Saint Joseph's University, Philadelphia, PA, USA
| | | | - James Wager-Miller
- Psychological and Brain Sciences Campus, Indiana University, Bloomington, IN, USA
| | - Milan Pophristic
- Research and Development, MSTM, LLC, Philadelphia, PA, USA
- Department of Chemistry & Biochemistry, Saint Joseph's University, Philadelphia, PA, USA
| | - Ken Mackie
- Psychological and Brain Sciences Campus, Indiana University, Bloomington, IN, USA
| | - Charles N McEwen
- Research and Development, MSTM, LLC, Philadelphia, PA, USA
- Department of Chemistry & Biochemistry, Saint Joseph's University, Philadelphia, PA, USA
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Euler L, Wagener F, Thomas A, Thevis M. Determination and enantioselective separation of zilpaterol in human urine after mimicking consumption of contaminated meat using high-performance liquid chromatography with tandem mass spectrometry techniques. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2022; 36:e9357. [PMID: 35851724 DOI: 10.1002/rcm.9357] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Revised: 07/15/2022] [Accepted: 07/16/2022] [Indexed: 06/15/2023]
Abstract
RATIONALE The synthetic β-adrenoreceptor agonist zilpaterol is legitimately used as an animal feed supplement in selected countries due to its known effects on lipolysis and protein biosynthesis. These pharmacological characteristics of zilpaterol have contributed to its classification as doping agent in sport by the World Anti-Doping Agency. However, the use as a feed supplement can lead to residues of the drug in edible tissues and, possibly, also in the urine of consumers. METHODS To provide urinary elimination profiles of microdosed zilpaterol and to determine whether the ingestion of zilpaterol below or at the acceptable daily intake level of 0.04 μg/kg bodyweight can result in an adverse analytical finding (AAF) in doping controls, healthy volunteers were administered single or multiple oral doses of 0.5 μg or 3 μg zilpaterol to mimic ingestion of contaminated cattle meat. Urine samples were collected and analyzed using a validated high-performance liquid chromatography-electrospray ionization-tandem mass spectrometry (HPLC-ESI-MS/MS) method and a newly developed chiral high-performance liquid chromatography-atmospheric pressure chemical ionization-tandem mass spectrometry (HPLC-APCI-MS/MS) method. RESULTS Urinary peak concentrations of zilpaterol were observed for all volunteers 1.5-12.5 h after ingestion, and maximum levels >5 ng/mL, which would constitute an AAF in doping controls, were found after the intake of 3 μg of zilpaterol on five consecutive days in one out of five study participants. Noteworthy, the enantiomeric ratio of excreted zilpaterol remained constant over time. CONCLUSION This study provides first insights into the urinary excretion of microdosed zilpaterol. Furthermore, a method was successfully developed and applied for the separation of the zilpaterol enantiomers with mass spectrometric detection.
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Affiliation(s)
- Luisa Euler
- Institute of Biochemistry/Center for Preventive Doping Research, German Sport University Cologne, Cologne, Germany
| | - Felicitas Wagener
- Institute of Biochemistry/Center for Preventive Doping Research, German Sport University Cologne, Cologne, Germany
| | - Andreas Thomas
- Institute of Biochemistry/Center for Preventive Doping Research, German Sport University Cologne, Cologne, Germany
| | - Mario Thevis
- Institute of Biochemistry/Center for Preventive Doping Research, German Sport University Cologne, Cologne, Germany
- European Monitoring Center for Emerging Doping Agents (EuMoCEDA), Cologne, Germany
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Winders TM, Serum EM, Smith DJ, Neville BW, Mia GK, Amat S, Dahlen CR, Swanson KC. Influence of hempseed cake inclusion on growth performance, carcass characteristics, feeding behavior and blood parameters in finishing heifers. J Anim Sci 2022; 100:6577173. [PMID: 35511706 PMCID: PMC9169985 DOI: 10.1093/jas/skac159] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2022] [Accepted: 04/28/2022] [Indexed: 11/13/2022] Open
Abstract
As the hemp industry continues to develop in the US, there is interest in feeding byproducts of industrial hemp production to livestock. A completely randomized design experiment using crossbred finishing heifers [initial body weight (BW) ± SE = 494 ± 10 kg] was conducted to determine the effects of feeding hempseed cake in a corn-based finishing diet (10% forage) formulated to meet or exceed ruminally degradable and metabolizable protein requirements on growth performance, carcass characteristics, feeding behavior, and plasma parameters. Dietary treatments were inclusion of 20% [dry matter (DM) basis] of: dried corn distillers grains plus solubles (DDGS, n = 16), or hempseed cake (HEMP, n = 15). Cattle were housed in two pens, had ad-libitum access to feed and water, and individual intakes and feeding behavior were monitored using the Insentec feeding system. Cattle were fed treatment diets for 111 days, and every 14 days BW were measured, and blood samples collected. Blood plasma was analyzed for glucose, urea nitrogen, and individual amino acids and results analyzed using repeated measures analysis in SAS. Final BW, average daily gain, gain:feed, and hot carcass weight decreased (P ≤ 0.05) by 2.3%, 7.7%, 7.7%, and 2.6% respectively in heifers fed the HEMP diet than in heifers fed the DDGS diet. Net energy for maintenance and gain (Mcal/kg of feed, DM basis), estimated based on heifer intake and performance, were greater (P = 0.02) for the DDGS diet than the HEMP diet. All other performance and carcass characteristics were not different (P ≥ 0.20) between treatments. Heifers fed the HEMP diet had greater (P < 0.05) plasma urea nitrogen concentration in samples from each collection day compared to heifers fed the DDGS diet, although there was a treatment by day interaction (P < 0.01) because of variability in the magnitude of treatment differences over time. Plasma glucose concentration was not influenced (P = 0.17) by dietary treatment. Plasma concentrations of total amino acids, non-essential amino acids, and essential amino acids were not different between treatments (P ≥ 0.09), although there were several interactions between treatment and day (P ≤ 0.04) for individual amino acids. These data suggest that hempseed cake has a lower NEm and NEg relative to dried corn distillers grains plus solubles when adequate metabolizable protein is supplied, while still providing adequate nutrition to support acceptable performance of finishing cattle.
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Affiliation(s)
- Thomas M Winders
- Department of Animal Sciences, North Dakota State University, Fargo, ND 58108-6050, USA
| | | | | | - Bryan W Neville
- Carrington Research Extension Center, Carrington, ND 58421-0219, USA
| | - Golam K Mia
- Department of Animal Sciences, North Dakota State University, Fargo, ND 58108-6050, USA
| | - Samat Amat
- Department of Microbiological Sciences, North Dakota State University, Fargo, ND 58108-6050, USA
| | - Carl R Dahlen
- Department of Animal Sciences, North Dakota State University, Fargo, ND 58108-6050, USA
| | - Kendall C Swanson
- Department of Animal Sciences, North Dakota State University, Fargo, ND 58108-6050, USA
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Dolores-Hernández M, Morales-Hipólito EA, Villaseñor A, López-Arellano R. Determination of zilpaterol in a residue depletion study using LC-MS/MS in cattle plasma, muscle, liver and kidney. Food Chem 2022; 382:132287. [PMID: 35139465 DOI: 10.1016/j.foodchem.2022.132287] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2021] [Revised: 12/30/2021] [Accepted: 01/26/2022] [Indexed: 11/04/2022]
Abstract
Zilpaterol is a β-agonist compound which promotes fat loss and muscle gain in cattle, providing economic benefits. However, zilpaterol residues in the animal might introduce a significant risk to humans after consumption. In the present manuscript, a highly specific, sensitive method using Selected Reaction Monitoring (SRM) in positive electrospray ionization (ESI +) mode by liquid chromatography coupled to triple quadrupole mass spectrometry (LC-MS/MS) for plasma, muscle, liver and kidney is presented. For method development, composition of the aqueous mobile phase, precipitation agent, and solid phase extraction (SPE) conditions were optimized. The method was fully validated showing a good linearity and recovery average greater than or equal to 97 % for all matrices. The method was applied to residue depletion studies in cattle after withdrawal of zilpaterol supplementation at 3, 4, 5 and 6 days showing that tissues can be consumed by humans after 4th day of zilpaterol withdrawal.
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Affiliation(s)
- Mariana Dolores-Hernández
- Laboratory of Pharmaceutical Development Tests, Multidisciplinary Research Unit (UIM), Faculty of Higher Education Cuautitlán, National Autonomous University of Mexico, Carr. Cuautitlán-Teoloyucan Km 2.5, San Sebastián Xhala, 54714 Cuautitlán Izcalli, Mexico
| | - Elvia A Morales-Hipólito
- Laboratory of Pharmaceutical Development Tests, Multidisciplinary Research Unit (UIM), Faculty of Higher Education Cuautitlán, National Autonomous University of Mexico, Carr. Cuautitlán-Teoloyucan Km 2.5, San Sebastián Xhala, 54714 Cuautitlán Izcalli, Mexico
| | - Alma Villaseñor
- IMMA, Instituto de Medicina Molecular Aplicada, Facultad de Medicina, San Pablo CEU Universities, Madrid, España
| | - Raquel López-Arellano
- Laboratory of Pharmaceutical Development Tests, Multidisciplinary Research Unit (UIM), Faculty of Higher Education Cuautitlán, National Autonomous University of Mexico, Carr. Cuautitlán-Teoloyucan Km 2.5, San Sebastián Xhala, 54714 Cuautitlán Izcalli, Mexico.
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Shelver WL, Chakrabarty S, Young JM, Byrd CJ, Smith DJ. Evaluation of rapid and standard tandem mass spectrometric methods to analyse veterinary drugs and their metabolites in antemortem bodily fluids from food animals. Food Addit Contam Part A Chem Anal Control Expo Risk Assess 2021; 39:462-474. [PMID: 34939883 DOI: 10.1080/19440049.2021.2006801] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Antemortem bodily fluids can serve as an indicator of veterinary medicine exposure prior to food animal slaughter. A multi-residue, rapid screen electrospray ionisation mass spectrometric (RS-ESI-MS) method was developed to analyse 10 veterinary drugs or metabolites (clenbuterol, erythromycin, flunixin, 5-hydroxyflunixin, meloxicam, ractopamine, ractopamine-glucuronide, salbutamol, tylosin, and zilpaterol) in hog oral fluid and bovine urine. Simple acetonitrile extraction with salting-out was employed to remove the analytes from matrices in less than 30 minutes. Instrumental analysis time was < 1 min/injection. Regression coefficients of matrix-matched calibration curves ranged 0.9743-0.9999 across all compounds with limits of detection ranging from 0.46-108 ng mL-1 for cattle urine and 0.19-64.4 ng mL-1 for hog oral fluid across all analytes. Except for ractopamine-glucuronide, analyte recoveries ranged from 92.7-106% for oral fluid and urine fortified at 30, 100, and 300 ng mL-1, with inter-day variations of < 25%. Ractopamine-glucuronide recovery was 93.3% for oral fluid fortified at 300 ng mL-1. The RS-ESI-MS method accurately identified ractopamine and/or ractopamine-glucuronide in incurred cattle urine with results correlating well with traditional LC-MS/MS and HPLC fluorescence methods. As far as we are aware, this is the first report of the direct quantification of ractopamine-glucuronide from biological matrices without lengthy hydrolysis and cleanup steps.
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Affiliation(s)
- Weilin L Shelver
- Edward T. Schafer Agricultural Research Center, Biosciences Research Laboratory, USDA-Agricultural Research Service, Fargo, ND, USA
| | | | - Jennifer M Young
- Department of Animal Sciences, North Dakota State University, Fargo, ND, USA
| | - Christopher J Byrd
- Department of Animal Sciences, North Dakota State University, Fargo, ND, USA
| | - David J Smith
- Edward T. Schafer Agricultural Research Center, Biosciences Research Laboratory, USDA-Agricultural Research Service, Fargo, ND, USA
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Han Z, Chen LC. Electrospray Ionization Inside the Ion Inlet Tube: Multijet Mode Operation. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2021; 32:1821-1828. [PMID: 34167294 DOI: 10.1021/jasms.1c00157] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
We investigated the electrospray ionization inside the narrow channel of the ion inlet tube. An insulating emitter capillary made of fused silica with a 0.2 mm outer diameter was inserted into the ion inlet tubes with a 0.5 and 0.6 mm inner diameter to aspirate all the charged droplets. A custom-made ion inlet tube with two side holes near its entrance is used to observe the spraying condition. The spray current is measured and monitored during the MS acquisition using isolation amplifiers. Because the emitter is cylindrically surrounded in close proximity by the metallic inner wall, it is difficult to obtain a stable and symmetric Taylor cone with its apex at the center of the emitter. Instead, a stable operation under a flow rate of 1-4 μL/min is found to be in the form of a multicone-jet mode with two or more Taylor cones anchoring around the rim of the emitter. The emitted charged droplet jets are dragged from hitting the wall by the fast-flowing air inside the inlet tube. Comparison with the typical cone-jet and multijet mode operated several millimeters outside the inlet capillary shows signal enhancements for protein standards.
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Affiliation(s)
- Zhongbao Han
- Faculty of Engineering, University of Yamanashi, 4-3-11, Takeda, Kofu, Yamanashi 400-8511, Japan
| | - Lee Chuin Chen
- Faculty of Engineering, University of Yamanashi, 4-3-11, Takeda, Kofu, Yamanashi 400-8511, Japan
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