Ion-Molecule Equilibria, How and Why

Kebarle, P.

doi:10.1016/1044-0305(92)85012-9

Cited by 29 publications

(15 citation statements)

References 43 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In most cases, the ion compositions can be at- In addition to the ion-molecule complexes, seemingly "odd" ions may result from ion-molecule reactions [36,[41][42][43]]. Only one "odd" ion, m r z 56 with the acetonitrile-water system, has significant intensity in our background spectra.…”

Section: Reagent Ionsmentioning

confidence: 99%

Ion formation of N-Methyl carbamate pesticides in thermospray mass spectrometry: The effects of additives to the liquid chromatographic eluent and of the vaporizer temperature

Honing

Barceló

Baar

et al. 1994

J. Am. Soc. Mass Spectrom.

View full text Add to dashboard Cite

The effects of three additives-ammonium acetate, ammonium formate, and nicotinic acid-to the liquid chromatographic (LC) eluent and of the vaporizer temperature on the ion formation of N-methyl carbamate pesticides in thermospray (TSP) mass spectrometry was investigated by using filament- or discharge-assisted ionization. Nineteen carbamates and 12 of their known environmental degradation products were used as model compounds. The additives cause a strong reduction in the abundance of the characteristic fragment ions [M + H - CH3NCO](+) and [M - H - CH3NCO](-) for some of the carbamates. The addition of nicotinic acid reduces the quasimolecular ion intensity and, in most cases, produces nicotinic acid adduct ions. The addition of ammonium acetate or ammonium formate increases the intensity of the quasimolecular ion and in most cases produces a base peak for the ammonium adduct ion. The combination of a suppression of fragmentation and an enhancement of quasimolecular ion formation produces an overall gain in sensitivity. As to more specific effects, the addition of the ammonium salts reduces the intensity of M(-•) with the chlorinated carbamate barban and suppresses the formation of "odd" adduct ions in the TSP mass spectra of most other carbamates. Monitoring the intensity of the fragment and the quasimolecular ion signal as a function of the probe stem temperature, and the related probe tip temperature, proved to be an easy method to study the thermal degradation of the carbamates. This monitoring procedure showed that methiocarb and its sulfone already suffer from thermal degradation at a stem temperature of 90°C and that these compounds will therefore present problems in quantitation with LC/TSP mass spectrometry.

show abstract

Section: Reagent Ionsmentioning

confidence: 99%

Ion formation of N-Methyl carbamate pesticides in thermospray mass spectrometry: The effects of additives to the liquid chromatographic eluent and of the vaporizer temperature

Honing

Barceló

Baar

et al. 1994

J. Am. Soc. Mass Spectrom.

View full text Add to dashboard Cite

show abstract

“…One can obtain intense molecular ions for many compounds via chemical ionization 3–5 . Though this method is sensitive, it is quite selective for different classes of compounds, and, therefore, the selection of reagent ions is required.…”

Section: Introductionmentioning

confidence: 99%

Ionization of organic molecules with metal ions formed in the laser plasma

et al. 2021

View full text Add to dashboard Cite

A laser plasma ion source was used to ionize volatile organic compounds in a gas sample. The plasma was generated on a metal target in the intermediate vacuum region of ~0.3 Torr using a pulsed Nd:YAG laser with a wavelength of 1 μm. The resulting ions mass spectra were acquired using orthogonal time‐of‐flight mass spectrometer (O‐TOF MS). When using a copper target, the ions formed are simple complexes (CuM+) of copper ions with organic molecules. The possibility of online identification of trace amounts of alkanes in nitrogen and air, with a detection limit of ~10 ppb, was demonstrated. The ionization efficiency of volatile organic compounds through the formation of clusters with metal ions is 10−4 in terms of the quasimolecular complex ions. The rate constants of ion‐molecular reactions of copper ions with octane and water molecules in nitrogen and air are estimated.

show abstract

“…Cycle 2, which corresponds to the oxidation of methane to formaldehyde (Eq. (79)), dominates at 210 K, while cycle 2 becomes competitive at 240 K and then dominates at temperatures of 250 to formaldehyde was predicted via DFT calculations. Each formaldehyde is formed at a different end of the gold dimer, and they are formed in the following related steps: oxygen absorbs at a gold site to form a peroxo intermediate, (CH 4 )Au-Au (O-O)(CH 4 ) + , which then abstracts a hydrogen atom to yield an organogoldhydroperoxide intermediate, (CH 4 )Au-Au(O-OH)(CH 3 ) + , which then loses water to form a oxo-gold-carbene, (CH 4 )Au-Au(O)(CH 2 ) + , that can then rearrange to the O bound formaldehyde complex, (CH 4 )Au-Au(OCH 2 ) + .…”

Section: Catalysis By Gold Cluster Ionsmentioning

confidence: 90%

“…There is a rich history on the use of mass spectrometry-based methods to measure the binding energies of substrates to metal ions and metal cluster ions using gas-phase ion-molecule reactions [31,[250][251][252][253][254][255][256][257]. Much of the earlier literature dealt with the thermochemistry associated with bare metal atomic cations [253].…”

Section: Thermochemistrymentioning

confidence: 99%

Gas Phase Formation, Structure and Reactivity of Gold Cluster Ions

Zavras

Khairallah

O’Hair

2014

Structure and Bonding

View full text Add to dashboard Cite

With the advent of electrospray ionisation (ESI) and matrix-assisted laser desorption ionisation (MALDI), mass spectrometry (MS) is now routinely used to establish the molecular formulae of gold nanoclusters (AuNCs). ESI-MS has been used to monitor the solution phase growth of AuNCs when gold salts are reduced in the presence of phosphine or thiolate ligands. Beyond this analytical role, over the past 2 decades MS-based methods have been employed to examine the fundamental properties and reactivities of AuNC ions. For example, ion mobility and spectroscopic measurements may be used to assign structures; thermochemical data provides important information on ligand binding energies; unimolecular chemistry can be explored; and ion-molecule reactions with various substrates can be used to probe catalysis by AuNC ions. MS can also be used to monitor and direct the synthesis of AuNC bulk material either by guiding solution phase synthesis conditions or by soft landing a beam of mass-selected (i.e. monodisperse) AuNC ions onto a surface. This review showcases all areas in which mass spectrometry has played a role in AuNC science.

show abstract

Ion-Molecule Equilibria, How and Why

Cited by 29 publications

References 43 publications

Ion formation of N-Methyl carbamate pesticides in thermospray mass spectrometry: The effects of additives to the liquid chromatographic eluent and of the vaporizer temperature

Ion formation of N-Methyl carbamate pesticides in thermospray mass spectrometry: The effects of additives to the liquid chromatographic eluent and of the vaporizer temperature

Ionization of organic molecules with metal ions formed in the laser plasma

Gas Phase Formation, Structure and Reactivity of Gold Cluster Ions

Contact Info

Product

Resources

About