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Strmeň T, Vrkoslav V, Bosáková Z, Cvačka J. Atmospheric pressure chemical ionization mass spectrometry at low flow rates: Importance of ion source housing. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2020; 34:e8722. [PMID: 31912928 DOI: 10.1002/rcm.8722] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2019] [Revised: 12/01/2019] [Accepted: 01/06/2020] [Indexed: 06/10/2023]
Abstract
RATIONALE Hyphenation of atmospheric pressure chemical ionization (APCI) mass spectrometry with capillary and micro high-performance liquid chromatography (HPLC) is attractive for many applications, but reliable ion sources dedicated to these conditions are still missing. There are a number of aspects to consider when designing such an ion source, including the susceptibility of the ionization processes to ambient conditions. Here we discuss the importance of ion source housing for APCI at low flow rates. METHODS Selected compounds dissolved in various solvents were used to study ionization reactions at 10 μL/min flow rate. APCI spectra were generated using the Ion Max-S source (Thermo Fisher Scientific) operated with or without the ion source housing. RESULTS The APCI spectra of most compounds measured in the open and enclosed ion sources were markedly different. The differences were explained by water and oxygen molecules that entered the plasma region of the open ion source. Water tended to suppress charge transfer processes while oxygen diminished electron capture reactions and prevented the formation of acetonitrile-related radical cations useful for localizing double bonds in lipids. The effects associated with the ion source housing were significantly less important for compounds that are easy to protonate or deprotonate. CONCLUSIONS The use of ion source housing prevented alternative ionization channels leading to unwanted or unexpected ions. Compared with the conventional flow rate mode (1 mL/min), the effects of ambient air components were significantly higher at 10 μL/min, emphasizing the need for ion source housing in APCI sources dedicated to low flow rates.
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Affiliation(s)
- Timotej Strmeň
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo nám. 2, CZ-166 10, Prague 6, Czech Republic
- Department of Analytical Chemistry, Faculty of Science, Charles University in Prague, Hlavova 2030/8, CZ-128 43, Prague 2, Czech Republic
| | - Vladimír Vrkoslav
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo nám. 2, CZ-166 10, Prague 6, Czech Republic
| | - Zuzana Bosáková
- Department of Analytical Chemistry, Faculty of Science, Charles University in Prague, Hlavova 2030/8, CZ-128 43, Prague 2, Czech Republic
| | - Josef Cvačka
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo nám. 2, CZ-166 10, Prague 6, Czech Republic
- Department of Analytical Chemistry, Faculty of Science, Charles University in Prague, Hlavova 2030/8, CZ-128 43, Prague 2, Czech Republic
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Vaikkinen A, Kauppila TJ, Kostiainen R. Charge Exchange Reaction in Dopant-Assisted Atmospheric Pressure Chemical Ionization and Atmospheric Pressure Photoionization. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2016; 27:1291-1300. [PMID: 27126470 DOI: 10.1007/s13361-016-1399-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2015] [Revised: 03/15/2016] [Accepted: 03/26/2016] [Indexed: 06/05/2023]
Abstract
The efficiencies of charge exchange reaction in dopant-assisted atmospheric pressure chemical ionization (DA-APCI) and dopant-assisted atmospheric pressure photoionization (DA-APPI) mass spectrometry (MS) were compared by flow injection analysis. Fourteen individual compounds and a commercial mixture of 16 polycyclic aromatic hydrocarbons were chosen as model analytes to cover a wide range of polarities, gas-phase ionization energies, and proton affinities. Chlorobenzene was used as the dopant, and methanol/water (80/20) as the solvent. In both techniques, analytes formed the same ions (radical cations, protonated molecules, and/or fragments). However, in DA-APCI, the relative efficiency of charge exchange versus proton transfer was lower than in DA-APPI. This is suggested to be because in DA-APCI both dopant and solvent clusters can be ionized, and the formed reagent ions can react with the analytes via competing charge exchange and proton transfer reactions. In DA-APPI, on the other hand, the main reagents are dopant-derived radical cations, which favor ionization of analytes via charge exchange. The efficiency of charge exchange in both DA-APPI and DA-APCI was shown to depend heavily on the solvent flow rate, with best efficiency seen at lowest flow rates studied (0.05 and 0.1 mL/min). Both DA-APCI and DA-APPI showed the radical cation of chlorobenzene at 0.05-0.1 mL/min flow rate, but at increasing flow rate, the abundance of chlorobenzene M(+.) decreased and reagent ion populations deriving from different gas-phase chemistry were recorded. The formation of these reagent ions explains the decreasing ionization efficiency and the differences in charge exchange between the techniques. Graphical Abstract ᅟ.
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Affiliation(s)
- Anu Vaikkinen
- Faculty of Pharmacy, University of Helsinki, P.O. Box 56 , (Viikinkaari 5 E), 00014, Helsinki, Finland
| | - Tiina J Kauppila
- Faculty of Pharmacy, University of Helsinki, P.O. Box 56 , (Viikinkaari 5 E), 00014, Helsinki, Finland
| | - Risto Kostiainen
- Faculty of Pharmacy, University of Helsinki, P.O. Box 56 , (Viikinkaari 5 E), 00014, Helsinki, Finland.
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Kim YH, Kim S. Improved abundance sensitivity of molecular ions in positive-ion APCI MS analysis of petroleum in toluene. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2010; 21:386-392. [PMID: 19962908 DOI: 10.1016/j.jasms.2009.11.001] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2009] [Revised: 10/30/2009] [Accepted: 11/02/2009] [Indexed: 05/28/2023]
Abstract
Positive-ion atmospheric pressure chemical ionization (APCI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) analyses of petroleum sample were performed with higher sensitivity by switching the solvent composition from toluene and methanol or acetonitrile to a one-component system consisting only of toluene. In solvent blends, molecular ions were more abundant than were protonated ions with increasing percentages of toluene. In 100% toluene, the double-bond equivalence (DBE) distributions of molecular ions obtained by APCI MS for each compound class were very similar to those obtained in dopant assisted atmospheric pressure photo ionization (APPI) MS analyses. Therefore, it was concluded that charge-transfer reaction, which is important in toluene-doped APPI processes, also plays a major role in positive-ion APCI. In the DBE distributions of S(1), S(2), and SO heteroatom classes, a larger enhancement in the relative abundance of molecular ions at fairly specific DBE values was observed as the solvent was progressively switched to toluene. This enhanced abundance of molecular ions was likely dependent on molecular structure.
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Affiliation(s)
- Young Hwan Kim
- Korea Basic Science Institute, Mass Spectrometry Team, Ochang, Republic of Korea
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Hommerson P, Khan AM, de Jong GJ, Somsen GW. Capillary electrophoresis-atmospheric pressure chemical ionization-mass spectrometry using an orthogonal interface: set-up and system parameters. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2009; 20:1311-1318. [PMID: 19349196 DOI: 10.1016/j.jasms.2009.03.005] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2009] [Revised: 03/04/2009] [Accepted: 03/05/2009] [Indexed: 05/27/2023]
Abstract
The feasibility of atmospheric pressure chemical ionization (APCI) as an alternative ionization technique for capillary electrophoresis-mass spectrometry (CE-MS) was investigated using a grounded sheath-flow CE-MS sprayer and an orthogonal APCI source. Infusion experiments indicated that highest analyte signals were achieved when the sprayer tip was in close vicinity of the vaporizer entrance. The APCI-MS set-up enabled detection of basic, neutral, and acidic compounds, whereas apolar and ionic compounds could not be detected. In the positive ion mode, analytes could be detected in the entire transfer voltage range (0-5 kV), whereas highest signal intensities were observed when the corona discharge current was between 1000 and 2000 nA. In the negative ion mode, the transfer voltage typically was 500 V and the optimum corona discharge current was 6000 nA. Analyte signals were raised with increasing nebulizing gas pressure, but the pressure was limited to 25 psi to avoid siphoning and current drops. Signal intensities appeared to be optimal and constant over a wide range of sheath liquid flow rate (5-25 microL/min) and vaporizer temperature (200-350 degrees C). APCI-MS signals were unaffected by the composition of the background electrolyte (BGE), even when it contained sodium phosphate and sodium dodecyl sulfate (SDS). Consequently, BGE composition, sheath-liquid flow rate, and vaporizer temperature can be optimized with respect to the CE separation without affecting the APCI-MS response. The analysis of a mixture of basic compounds and a steroid using volatile and nonvolatile BGEs further demonstrates the feasibility of CE-APCI-MS. Detection limits (S/N = 3) were 1.6-10 microM injected concentrations.
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Affiliation(s)
- Paul Hommerson
- Department of Biomedical Analysis, Utrecht University, Utrecht, The Netherlands.
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Effect of eluent on the ionization process in liquid chromatography–mass spectrometry. J Chromatogr A 2009; 1216:685-99. [DOI: 10.1016/j.chroma.2008.08.095] [Citation(s) in RCA: 302] [Impact Index Per Article: 20.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2008] [Revised: 08/01/2008] [Accepted: 08/28/2008] [Indexed: 11/22/2022]
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Moriwaki H, Miyakoda H. Analysis of p,p'-dichlorodiphenyltrichloroethane (p,p'-DDT) by liquid chromatography/atmospheric pressure photoionization-mass spectrometry. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2007; 21:1090-2. [PMID: 17310503 DOI: 10.1002/rcm.2936] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
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Guella G, Ascenzi D, Franceschi P, Tosi P. The intriguing case of organic impurities contained in synthetic methanol: a mass spectrometry based investigation. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2007; 21:3337-44. [PMID: 17879386 DOI: 10.1002/rcm.3222] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
The role of organic impurities in the methanol-to-olefin (MTO) industrial process catalyzed by zeolites is the subject of ongoing debate. We have found that methanol (HPLC and RPE grade) purchased from different chemical companies may contain organic impurities, whose ionization is the dominant process in the positive ion atmospheric pressure chemical ionization (APCI) spectrum of commercial CH(3)OH. Such impurities produce ions with elemental formulae C(n)H(2n+1)O(+) (n = 4, 5, 6); likewise, ionization of tetradeuterated methanol (CD(3)OD) leads to the corresponding fully deuterated series C(n)D(2n+1)O(+) (n = 4, 5, 6), an outcome which represents a clear evidence of their widespread diffusion. We suggest that their formation might be inherent to the chemical process whereby methanol is synthesized on an industrial scale. Mass spectrometry (MS) experiments, gas chromatography/mass spectrometry (GC/MS) analysis and nuclear magnetic resonance (NMR) measurements allowed us to establish that commercial methanol contains dimethyl acetals of simple alkyl ketones, such as propanone, butanone and pentanone. Ab initio calculations (DFT/B3LYP) proved useful to understanding the ionization mechanisms of such impurities.
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Affiliation(s)
- Graziano Guella
- Department of Physics, Università degli Studi di Trento, Via Sommarive 14, I-38050 Povo, Trento, Italy.
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Ascenzi D, Franceschi P, Guella G, Tosi P. Phenol Production in Benzene/Air Plasmas at Atmospheric Pressure. Role of Radical and Ionic Routes. J Phys Chem A 2006; 110:7841-7. [PMID: 16789771 DOI: 10.1021/jp062406p] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Benzene can be efficiently converted into phenol when it is treated by either corona or dielectric barrier discharge (DBD) plasmas operating at atmospheric pressure in air or mixtures of N(2) and O(2). Phenol produced by corona discharge in an atmospheric pressure chemical ionization source (APCI) has been detected as the corresponding radical cation C(6)H(5)OH(+*) at m/z 94 by an ion trap mass spectrometer. On the other hand, phenol has been observed also as neutral product by gas chromatography-mass spectrometry analysis (GC-MS) after treatment in a DBD plasma. Experiments aimed at shading light on the elementary processes responsible for benzene oxidation were carried out (i) by changing the composition of the gas in the corona discharge source; (ii) by using isotopically labeled reagents; and (iii) by investigating some relevant ion-molecule reactions (i.e. C(6)H(6)(+*) + O(2), C(6)H(5)(+) + O(2)) via selected guided ion beam measurements and with the help of ab initio calculations. The results of our approach show that ionic mechanisms do not play a significant role in phenol production, which can be better explained by radical reactions resulting in oxygen addition to the benzene ring followed by 1,2 H transfer.
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Affiliation(s)
- Daniela Ascenzi
- Dipartimento di Fisica, Universita di Trento, Povo (TN), Italy.
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Cotte-Rodríguez I, Justes DR, Nanita SC, Noll RJ, Mulligan CC, Sanders NL, Cooks RG. Analysis of gaseous toxic industrial compounds and chemical warfare agent simulants by atmospheric pressure ionization mass spectrometry. Analyst 2006; 131:579-89. [PMID: 16568176 DOI: 10.1039/b513605a] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The suitability of atmospheric pressure chemical ionization mass spectrometry as sensing instrumentation for the real-time monitoring of low levels of toxic compounds is assessed, especially with respect to public safety applications. Gaseous samples of nine toxic industrial compounds, NH3, H2S, Cl2, CS2, SO2, C2H4O, HBr, C6H6 and AsH3, and two chemical warfare agent simulants, dimethyl methylphosphonate (DMMP) and methyl salicylate (MeS), were studied. API-MS proves highly suited to this application, with speedy analysis times (<30 seconds), high sensitivity, high selectivity towards analytes, good precision, dynamic range and accuracy. Tandem MS methods were implemented in selected cases for improved selectivity, sensitivity, and limits of detection. Limits of detection in the parts-per-billion and parts-per-trillion range were achieved for this set of analytes. In all cases detection limits were well below the compounds' permissible exposure limits (PELs), even in the presence of added complex mixtures of alkanes. Linear responses, up to several orders of magnitude, were obtained over the concentration ranges studied (sub-ppb to ppm), with relative standard deviations less than 3%, regardless of the presence of alkane interferents. Receiver operating characteristic (ROC) curves are presented to show the performance trade-off between sensitivity, probability of correct detection, and false positive rate. A dynamic sample preparation system for the production of gas phase analyte concentrations ranging from 100 pptr to 100 ppm and capable of admixing gaseous matrix compounds and control of relative humidity and temperature is also described.
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Guella G, Franceschi P, Tosi P. Structure and stability of oligomeric clusters produced in the ionization of acetonitrile. Chem Phys Lett 2005. [DOI: 10.1016/j.cplett.2005.09.012] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Current literature in mass spectrometry. JOURNAL OF MASS SPECTROMETRY : JMS 2005; 40:1110-21. [PMID: 16106339 DOI: 10.1002/jms.809] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
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