Comparative sulphur cation chemistry in a hydrocarbon flame with H2S, OCS, and SO2 additives

1986 ◽  
Vol 64 (12) ◽  
pp. 2412-2417 ◽  
Author(s):  
Nicholas S. Karellas ◽  
John M. Goodings
Keyword(s):  
Reaction Zone ◽  
Atmospheric Pressure ◽  
Mass Spectra ◽  
Chemical Ionization ◽  
Negative Ions ◽  
Mass Range ◽  
Total Ionization ◽  
Ion Recombination ◽  
Diffusion Mass ◽  
Oxygen Flame

A fuel-rich, conical, premixed, methane–oxygen flame at atmospheric pressure was doped separately with 0.2 mol% of H2S, OCS, and SO2 to probe the chemistry of sulphur at its source during combustion. These three additives represent a broad range of fuel-sulphur contaminants since they occur early, intermediate, and late in the sulphur oxidation sequence. A wide variety of sulphurous cations, formed by chemical ionization reactions, is observed for each additive by sampling the flame into a mass spectrometer. The total ionization profile measured along the flame axis is enhanced in the reaction zone when a sulphur additive is present; the mechanism involves the formation of sulphurous negative ions which reduces the rates of cation loss by electron–ion recombination and ambipolar diffusion. Mass spectra measured in the mass range 10–110 u at fixed points on the flame axis are very similar for all three additives, and are not helpful in the identification of the additive. However, the general presence of sulphur is evident from large signals measured near the reaction zone at five principal mass numbers; namely, 45 u (CHS+), 47 u (CH3S+), 58 u (C2H2S+), 59 u (C2H3S+), and 69 u (C3HS+) related to CS, thioformaldehyde, thioketene, and C3S.

Sulphur cation chemistry in a fuel-rich, CH4–O2 flame with OCS additive

1986 ◽  
Vol 64 (9) ◽  
pp. 1733-1742 ◽  
Author(s):  
Nicholas S. Karellas ◽  
John M. Goodings
Keyword(s):  
Reaction Zone ◽  
Atmospheric Pressure ◽  
Mass Spectra ◽  
Mass Range ◽  
Major Product ◽  
Premixed Flame ◽  
Ion Concentration ◽  
Concentration Profiles ◽  
Ion Chemistry ◽  
Ion Molecule Reactions

A fuel-rich, methane–oxygen, premixed flame at atmospheric pressure was doped with 0.2 mol% of OCS. More than 40 different sulphurous cations were observed in the mass range < 100 u by sampling the flame into a flame-ion mass spectrometer. Ion concentration profiles along the flame axis are presented, together with mass spectra at fixed points in the flame. In the reaction zone, primary sulphur ions CHxS+ (x = 1, 3, 5) undergo extensive ion–molecule reactions (association and condensation) with CH4/CH3, C2H2, and OCS to form a considerable variety of secondary sulphurous cations. Just downstream of the reaction zone, the ion chemistry is somewhat different; it appears to be dominated by reactions of primary sulphur ions including HxS+ (x = 0–3) with C2H2 present as an intermediate. A few ions (HxS+, OS+, S2+) persist throughout the burnt gas region in equilibrium with the natural flame ions CHO+ and H3O+. These sulphurous cation signals show the evolution of the sulphur chemistry, both ionic and neutral, through the flame reaction zone into the burnt gas downstream where H2S, not SO2, is the major product in fuel-rich combustion.

Ion chemistry of second-row transition metals in hydrocarbon flames: cations and anions of Y, Zr, Nb, and Mo

1995 ◽  
Vol 73 (12) ◽  
pp. 2263-2271 ◽  
Author(s):  
Christine C.Y. Chow ◽  
John M. Goodings
Keyword(s):  
Transition Metals ◽  
Gas Phase ◽  
Atmospheric Pressure ◽  
Chemical Ionization ◽  
Negative Ions ◽  
Ion Concentration ◽  
Oxidation States ◽  
Metallic Ions ◽  
Ion Chemistry ◽  
Hydrocarbon Flames

A pair of laminar, premixed, CH4–O2 flames above 2000 K at atmospheric pressure, one fuel-rich (FR) and the other fuel-lean (FL), were doped with ~10−6 mol fraction of the second-row transition metals Y, Zr, Nb, and Mo. Since these hydrocarbon flames contain natural ionization, metallic ions were produced in the flames by the chemical ionization (CI) of metallic neutral species, primarily by H3O+ and OH− as CI sources. Both positive and negative ions of the metals were observed as profiles of ion concentration versus distance along the flame axis by sampling the flames through a nozzle into a mass spectrometer. For yttrium, the observed ions include the YO+•nH2O (n = 0–3) series, and Y(OH)4−. With zirconium, they include the ZrO(OH)+•nH2O (n = 0–2) series, and ZrO(OH)3−. Those observed with niobium were the cations Nb(OH)3+ and Nb(OH)4+, and the single anion NbO2(OH)2−. For molybdenum, they include the cations MoO(OH)2+ and MoO(OH)3+, and the anions MoO3− and MoO3(OH)−. Not every ion was observed in each flame; the FL flame tended to favour the ions in higher oxidation states. Also, flame ions in higher oxidation states were emphasized for these second-row transition metals compared with their first-row counterparts. Some ions written as members of hydrate series may have structures different from those of simple hydrates; e.g., YO+•H2O = Y(OH)2+ and ZrO(OH)+•H2O = Zr(OH)3+, etc. The ion chemistry for the production of these ions by CI in flames is discussed in detail. Keywords: transition metals, ions, flame, gas phase, negative ions.

Gas-Liquid Chromatographic-Mass Spectrometric Confirmation of Endosulfan and Endosulfan Sulfate in Apples and Carrots

1981 ◽  
Vol 64 (5) ◽  
pp. 1208-1210
Author(s):  
Perry S Wilkes
Keyword(s):  
Mass Spectra ◽  
Chemical Ionization ◽  
Mass Range ◽  
Mass Spectrometric ◽  
Chromatographic Retention ◽  
Gas Liquid Chromatography ◽  
Endosulfan Sulfate ◽  
Gasliquid Chromatography ◽  
Liquid Chromatographic ◽  
Chromatographic Mass

Abstract A gas-liquid chromatography-mass spectrometric (GLC-MS) procedure is described for the confirmation of endosulfan I, endosulfan II, and endosulfan sulfate in apples and carrots. After extraction, cleanup, and determination by electron capture gasliquid chromatography using current AOAC methodology, residues are confirmed by GLC-MS. The chemical ionization (CI) mode is used with methane as a reagent gas. Each residue is confirmed by a scan of only 4 regions of its mass spectrum rather than the full mass range. The 4 mass regions for the 2 endosulfan isomers are 274-280, 340-346, 368-374, and 404-412 atomic mass units (amu). For endosulfan sulfate, the mass regions are 286-294, 322-330, 384-392, and 420-428 amu. Four ions and their chlorine isotopic distributions are detected for each compound by this scanning technique. This method was developed by using carrots and apples to which had been added 0.1 ppm (50% of the current legal tolerance on carrots) of each of the 3 pesticides. The gas chromatographic retention times and the mass spectra of the 4 mass regions specified for the 3 pesticides were compared to those of reference standards injected under identical GLC-MS conditions and were used as the basis for confirming identity of the 3 compounds.

scholarly journals An Organic Chemist’s Guide to Electrospray Mass Spectrometric Structure Elucidation

Molecules ◽  
2019 ◽  
Vol 24 (3) ◽  
pp. 611 ◽  
Author(s):  
Arnold Steckel ◽  
Gitta Schlosser
Keyword(s):  
Atmospheric Pressure ◽  
Structure Elucidation ◽  
Mass Spectra ◽  
Chemical Ionization ◽  
Atmospheric Pressure Chemical Ionization ◽  
Collision Induced Dissociation ◽  
Tandem Mass ◽  
Tandem Mass Spectra ◽  
Pressure Chemical Ionization ◽  
Pressure Chemical

Tandem mass spectrometry is an important tool for structure elucidation of natural and synthetic organic products. Fragmentation of odd electron ions (OE+) generated by electron ionization (EI) was extensively studied in the last few decades, however there are only a few systematic reviews available concerning the fragmentation of even-electron ions (EE+/EE−) produced by the currently most common ionization techniques, electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI). This review summarizes the most important features of tandem mass spectra generated by collision-induced dissociation fragmentation and presents didactic examples for the unexperienced users.

Comparison of Gas Chromatographic/Mass Spectrometric and Liquid Chromatographic/Mass Spectrometric Methods for Confirmation of Coumaphos and Its Oxygen Analog in Eggs and Milk

1983 ◽  
Vol 66 (6) ◽  
pp. 1358-1364
Author(s):  
Kevin D White ◽  
Zhao Min ◽  
William C Brumley ◽  
Richard T Krause ◽  
James A Sphon
Keyword(s):  
Mass Spectra ◽  
Chemical Ionization ◽  
Negative Ions ◽  
Mass Spectrometric ◽  
Ionization Mass ◽  
Organophosphate Insecticide ◽  
Ion Detection ◽  
Oxygen Analog ◽  
Liquid Chromatographic ◽  
Chromatographic Mass

Abstract A comparison of a liquid chromatographic (LC)/mass spectrometric (MS) procedure for confirming coumaphos, an organophosphate insecticide, and its oxygen analog in milk and eggs with a capillary gas chromatographic (GO/MS method is presented. For the confirmation of coumaphos and its oxygen analog, multiple ion detection of both positive and negative ions from the chemical ionization mass spectra was used. Samples of milk and eggs fortified with the 2 compounds at the 0.1,0.01, and 0.005 ppm levels were analyzed. The major finding is the relatively greater efficiency of the LC/MS interface compared with the GC/MS capillary injector.

Silicon cation and anion chemistry in a fuel-rich, methane–oxygen flame

1992 ◽  
Vol 70 (4) ◽  
pp. 1069-1081 ◽  
Author(s):  
J. Hugh Horton ◽  
John M. Goodings
Keyword(s):  
Nucleophilic Substitution ◽  
Atmospheric Pressure ◽  
Chemical Ionization ◽  
Orthosilicic Acid ◽  
Ion Chemistry ◽  
Silicon Ions ◽  
Normal Carbon ◽  
Silicon Chemistry ◽  
Three Body ◽  
Oxygen Flame

Silicon cations and anions in a fuel-rich, premixed, methane–oxygen flame at atmospheric pressure doped with 0.01 mol% of trimethylsilane were observed by sampling the flame through a nozzle into a mass spectrometer. Twelve cations were observed which can be grouped into five series: SiOH+.nH2O (n = 0–2); SiOCH3+.nH2O (n = 0–2); Si(OH)3+.nH2O (n = 0–2); cations by nucleophilic substitution (e.g., Si(OH)(CH3)2(H2O)+); and carbonaceous aromatic cations (c-HSiCH=CH+ and c-HSiCH=CCH3+). Similarly, five anions were observed as members of two series: HxSiO3− (x = 0, 1) and HxSiO4− (x = 1–3). The chemical ionization reactions for the formation of these ions are discussed in detail, including proton transfer and also methyl cation transfer, three-body addition, nucleophilic substitution (SN2) of both the ions themselves and also their neutral silicon precursors, and H-atom abstraction reactions. The neutral silicon chemistry in the flame is dominated by SiO, but evidence was obtained from both the cation and the anion chemistry for the presence of HSiO(OH), silanoic acid; SiO(OH)2, metasilicic acid; and Si(OH)4, orthosilicic acid. The silicon ion chemistry differs markedly from the normal carbon ion chemistry that occurs naturally in the undoped methane–oxygen flame; the silicon ions show a strong tendency towards Si—O bond formation. Consideration is given to the probable structures of the various silicon cations and anions observed.

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