Reactions of selected molecular anions with oxygen

Knighton, W. B.; Bognar, John; Grimsrud, E. P.

doi:10.1002/jms.1190300406

Cited by 23 publications

(21 citation statements)

References 29 publications

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“…This equation has been derived from the statistical mechanical treatment of the equilibrium condition, M + e = M-, and the phenomenological rate constant for the forward reaction, k,,, which is often known from direct measurements. Although very few TED rate constants have been reported, those reported for the molecular anions of azulene (59) and perfluorobenzene (60) have been shown to be in good agreement with predictions derived from Eq. (3).…”

Section: E Thermal Electron Detachmentsupporting

confidence: 70%

“…1, this condition will exist if the EA is less than about 16 kcal/mol for very strongly responding compounds with k,, = 1 X cm3 s-', and if the E A is less than about 12 kcal/mol for moderately responding compounds with k,, = 1 X cm3 s-' at 150°C. The above consideration of TED explains why many classes of compounds that are known to have (60), which is known to capture electrons readily with k,, = 2 X lo-' cm3 s-l (35), but has an E A of only 12 kcal/mol (34). Also, numerous polycyclic aromatic hydrocarbons (PAH) having EA values of less than about 12 kcal mol-' behave in this manner, and their molecular anions are not sensitively detected by HPECMS with ion source temperatures of about 150°C or greater.…”

Section: E Thermal Electron Detachmentmentioning

confidence: 98%

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High‐pressure electron capture mass spectrometry

Knighton

Sears

Grimsrud

1995

Mass Spectrometry Reviews

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High‐pressure Electron Capture Mass Spectrometry (HPECMS) has demonstrated extraordinarily high chemical specificity and sensitivity in the analysis of numerous compounds of environmental and biomedical interest. In the application of this technique, however, difficulties in the form of unexpected EC mass spectra and unexplainable variations of sensitivity are often noted. In this review article, two distinct sets of processes that determine the nature of the ions produced in an HPEC ion source are reviewed and discussed. The first set of gas‐phase processes comprises the electron capture mechanism, leading to simple fragment and molecular anions. The second set of processes is imposed by physical realities of the typical HFEC ion source, These secondary processes can have large effects on the sensitivity of HPECMS to various types of EC‐active compounds and can lead to the production of unexpected ions in HPEC mass spectra. It will be shown that the successful use of HPECMS is greatly facilitated by an understanding of all of the above interactive factors. The scope of this review is limited to the processes that will be important only under the relatively pristine ion source conditions that are typically established for the trace analysis of EC‐active compounds introduced in very small quantities by capillary‐column gas chromatography. © 1996 John Wiley & Sons, Inc.

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Section: E Thermal Electron Detachmentsupporting

confidence: 70%

Section: E Thermal Electron Detachmentmentioning

confidence: 98%

High‐pressure electron capture mass spectrometry

Knighton

Sears

Grimsrud

1995

Mass Spectrometry Reviews

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“…It is no doubt that the reduction potential of chlorinated benzene increases with the chlorination level. The electron affinities of 1,2-DCB, PeCB, and HCB were estimated to be 0.09, 0.73, and 1.0 eV, respectively [16][17][18]. As the reduction potential of polychlorinated aromatic compound increases with the increase of chlorination, the oxidative destruction of chlorinated compound by V 2 O 5 /TiO 2 is unfavorable.…”

Section: Sv ¼ Flow Rate=volume Of Catalystmentioning

confidence: 99%

Catalytic Conversions of Polychlorinated Benzenes and Dioxins with Low-chlorine Using V2O5/TiO2

Lee

Jurng

2007

Catal Lett

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Chlorinated benzene, especially 1,2-dichlorobenzene (1,2-DCB), has been widely used as one of surrogate compounds of dioxin to find the noble methods to control dioxin. However, the relationship between the catalytic activity of dioxin surrogate compound and dioxin has not been understood quite well. In this work, we used a vanadium based catalyst (V 2 O 5 /TiO 2 ) to compare catalytic activity of chlorinated benzenes and dibenzo-p-dioxins with low-chlorine content using the lab-scale system. We investigated the catalytic conversions of low-chlorinated dioxins, [2-monochlorodibenzo-p-dioxin (2-MCDD), 2,3-dichlorodibenzo-p-dioxin (2,3-DCDD)] and polychlorinated benzenes [1,2-DCB, 1,2,3,4-tetrachlorobenzene (1,2,3,4-TeCB), pentachlorobenzene (PeCB), hexachlorobenzene (HCB)] using a V 2 O 5 /TiO 2 catalyst to understand quantitative relationship between dioxin and benzene with the chlorination level. The catalytic decomposition of chlorinated aromatic compounds was following 1,2-DCB > 1,2,3,4-TeCB > 2-MCDD > PeCB ≥ 2,3-DCDD > HCB. It might be more reasonable that PeCB or HCB should be used as the dioxin surrogate compound rather than 1,2-DCB. Also, we investigated the effect of both O 2 content and space velocity (SV) on the catalytic decomposition of 1,2-DCB in the presence of V 2 O 5 /TiO 2 catalyst because these factors should be considered significantly in combustion facilities to control various pollutants. The decomposition of 1,2-DCB shows dependency on the SV while the effect of oxygen content on the catalytic decomposition is negligible in the range of 5-20%.

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“…3,5 Methyl sulfone-substituted polychlorinated biphenyl compounds are responsive to ECNI-(MeSO 2 -PCB) MS.9,10 The 3-and ( Fig. 1) -PCB ECNI mass spectra and the e †ect of congener structure on the ECNI-MS fragmentation of 24, 3-and 4-MeSO 2 -PCBs in an oxygen-free GC/ECNI-MS system were examined.…”

Section: Introductionmentioning

confidence: 99%

Electron Capture/Negative Ionization Mass Spectrometric Characteristics of Bioaccumulating Methyl Sulfone-Substituted Polychlorinated Biphenyls

Letcher

Norstrom²

1997

J. Mass Spectrom.

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Gas chromatography/electron‐capture negative ionization mass spectrometry (GC/ECNI‐MS) was used to separate and detect a mixture of 24, 3‐and 4‐methyl sulfone‐substituted polychlorinated biphenyls (MeSO2‐PCBs). The dominant fragment ions were [M‐CH3]‐ and [M‐Cl+H]‐, and to a lesser extent [M‐2Cl]‐, [M‐2Cl+2H]‐, [M‐CH3‐Cl+H]‐ and [M‐SO2CH3+H]‐). The structures of the 3‐and 4‐MeSO2‐PCBs varied in the degree (i.e. tetrachloro‐to heptachloro‐) and position of chlorine substitution. With the assistance of multivariate statistical analysis, the abundance of several isotopic clusters of fragment ions relative to that of the molecular ion (M‐) was found to vary as a function of MeSO2‐PCB structure. Compared with other congeners, the relative abundance of [M‐CH3]‐ was significantly lower for MeSO2‐PCBs containing the 4‐MeSO2‐2,5‐dichloro moiety, and the hexachloro‐and heptachloro‐MeSO2‐PCBs had higher relative abundances of [M‐Cl+H]‐. Subtle ECNI mass spectral fragmentation rules therefore exist for 3‐and 4‐MeSO2‐PCBs with respect to congener structure; however, both ion source temperature and pressure must be controlled. Increasing the ion source temperature from 100 to 260°C resulted in an large increase in the abundance of [M‐CH3]‐ relative to M‐ from <20% to >100%, for all the MeSO2‐PCBs studied. For the set of ten 3‐/4‐MeSO2‐PCB pairs, the [M‐CH3]‐ relative abundance ratio was independent of ion source temperature, and was ∽4.5 and ∽1.5 for congeners possessing 2,5‐dichloro and 2,5,6‐trichloro substitution on the MeSO2‐containing phenyl ring, respectively. The effect of an increase in ion source temperature, over the same temperature range, on the relative abundance of hydrogen inclusion‐type fragment ions was much less dramatic. [M‐CH3‐Cl+H]‐ and [M‐Cl+H]‐ abundance often increased, but never exceeded ∽40%. Decreasing the methane reagent gas pressure from 0.5 to 0.05 mbar did not significantly alter the ion source temperature effect on the relative abundance of the fragment ions. However, the ECNI response sensitivity decreased by an order of magnitude. © 1997 by John Wiley & Sons, Ltd.

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Reactions of selected molecular anions with oxygen

Cited by 23 publications

References 29 publications

High‐pressure electron capture mass spectrometry

High‐pressure electron capture mass spectrometry

Catalytic Conversions of Polychlorinated Benzenes and Dioxins with Low-chlorine Using V2O5/TiO2

Electron Capture/Negative Ionization Mass Spectrometric Characteristics of Bioaccumulating Methyl Sulfone-Substituted Polychlorinated Biphenyls

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