Search results for " ionization"

Separation and determination of alkylglycosides by liquid chromatography with electrospray mass spectrometric detection

2007

The separation of alkylpolyglycosides by liquid chromatography with electrospray mass spectrometric detection, using either an alkylamide or a cyanopropyl column, and acetonitrile/water mixtures as mobile phases, was developed. Using the alkylamide column and isocratic elution, the alpha- and beta-epimers and ring isomers (pyranosides and furanosides) of the alkylmonoglycosides were resolved. The ring isomers were also resolved in a much shorter time using the cyanopropyl column with gradient elution. Using these columns, the isomers of the alkyldiglycosides and alkyltriglycosides were also partially resolved. The equilibration time was much shorter with the cyanopropyl column, which was se…

Surfactant self-assembling in the gas phase: bis(2-ethylhexyl)-sulfosuccinate divalent metal ion anionic aggregates

2012

RATIONALE Investigation of fundamental aspects driving surfactant self-assembling and of the capability of including guest molecules or ions in their micellar aggregates is an exciting research field for theoretical and technological reasons. In this light, assembling and chelating properties of sodium bis(2-ethylhexyl)sulfosuccinate (AOTNa) towards divalent metal ion chlorides have been investigated in the gas phase by electrospray ionization mass spectrometry in negative ion mode, tandem mass spectrometry and energy-resolved mass spectrometry. METHODS Water/methanol solutions of AOTNa and chloride salts of nickel, magnesium, calcium and manganese, with different AOTNa/metal salt ratios, w…

Positive and negative electrospray ionization-collision-induced dissociation of sulfur- containing zwitterionic liquids.

2011

The mass spectrometric properties of several (1,2-dimethyl-1 H-imidazol-3-ium-3-yl)-alkane-1-sulfonates (alkane=ethyl, propyl and butyl) are investigated in this study. These substances, named zwitterionic liquids (ZILs), were synthesized using classical transformations and analyzed in positive and negative electrospray ionization mode using collision-induced dissociation (0–50 eV). We have also performed regioselective deuterium labeling of the alkyl chain of 3-(1,2-dimethyl-1 H-imidazol-3-ium-3-yl)-propane-1-sulfonates. Thus, the mass spectra of isotopically-labeled compounds were used for the confirmation of fragmentation pathways of ZILs. Briefly, the data obtained in this study show t…

1978

The thermal degradation mechanism of three aromatic polymers containing double bridged phenylether units was investigated by direct pyrolysis in the ion source of a mass spectrometer. Thermal degradation reactions were followed directly by this method detecting the thermal and electron impact induced fragments. The results obtained have provided evidence that the double bridge between the aromatic rings is the preferred fragmentation site in these polymers. Furthermore in the double sulfur bridged polymer III, extrusion of S2 from the polymer backbone takes place above 400°C. The synthesis of polymers studied is reported in the text. Der Mechanismus des thermischen Abbaus von drei aromatisc…

The Synergetic Interplay of Weak Interactions in the Ion-Pair Recognition of Quaternary and Diquaternary Ammonium Salts by Halogenated Resorcinarenes

2013

The influence of halogens on the noncovalent interactions of different upper-rim-substituted hexylresorcinarenes with quaternary and diquaternary ammonium iodide salts was investigated in the gas phase by electrospray ionization Fourier-transform ion-cyclotron-resonance (ESI-FTICR) mass spectrometry and in solution by 1H NMR titration studies. The electronic nature of the substituents on the upper rim of the resorcinarene was directly reflected in the order of binding strengths of the hosts towards quaternary and diquaternary ammonium cations in the gas phase. In solution, the opposite trend was observed, with generally higher binding constants for the diquaternary over the quaternary salts…

Hydrogen-carbon, carbon-carbon double rearrangement induced by proximity effects. 1-formation of methoxybenzyl ions in the electron impact mass spect…

1991

The 75 eV electron impact mass spectra of 1,1-bis(dimethoxyphenyl)methanes bearing o-methoxy groups are dominated by intense peaks corresponding, at least formally, to benzyl ions [(CH3O)2C6H3CH2]+(b). They arise from ions [((CH3O)2C6H3)2CH]+(a), which are in turn formed from molecular ions by loss of an alkyl radical through benzylic cleavage. The analysis of compounds labelled with 2H or 13C at methoxy groups led to the determination of the mechanism. Hydrogen migration, as hydride, followed by electrophilic substitution by the methylene carbon of the phenyl methylene ether cation through a six-centred transition state is responsible for the formation of benzylic ions b.

Evaporation of tungsten oxides: A mass-spectrometric study of the vapour contents

1995

Abstract The evaporation of bulk oxides of WO2 and WO3 and oxidised tungsten surfaces (metallic tungsten heated in an oxygen atmosphere) have been studied by the means of mass-spectrometry. The principal constituents of the vapour are found to be molecules of WO2, WO3, W2O6 and W3O9. These results differ from earlier reports, where the presence of molecules smaller than W3O9 in the mass-spectrum was interpreted as an artifact due to electron impact dissociation of larger polymers.

Synthesis, characterization, cytotoxic activity and crystal structures of tri- and di-organotin(IV) complexes constructed from the β-{[(E)-1-(2-hydro…

2006

Abstract Reactions of potassium β-{[(E)-1-(2-hydroxyaryl)alkylidene]amino}propionates (L1HK-L3HK) and potassium β-{[(2Z)-(3-hydroxy-1-methyl-2- butenylidene)]amino}propionate (L4HK) with R3SnCl (R = Ph and nBu) and nBu2SnCl2 yielded complexes of composition Ph3SnL1H (1), Ph3SnL2H (2), Ph3SnL4H (3), nBu3SnL1H (4), and {[nBu2Sn(L2H)]2O}2 (5) and {[nBu2Sn(L3H)]2O}2 (6), respectively. These complexes have been characterized by 1H, 13C, 119Sn NMR, ESI-MS, IR and 119mSn Mossbauer spectroscopic techniques in combination with elemental analyses. The crystal structures of 1, 4, 5 and 6 were determined. In the solid state, compound 1 is a one-dimensional polymer built from SnPh3 moieties bridged by s…

Occurrence of glycine in the core oligosaccharides of Hafnia alvei lipopolysaccharides--identification of disubstituted glycoform.

2015

Endotoxins (lipopolysaccharides, LPS) are the main surface antigens and virulence factors of Gram-negative bacteria involved for example in the development of nosocomial infections and sepsis. They consist of three main regions: O-specific polysaccharide, core oligosaccharide, and lipid A. Bacteria modify LPS structure to escape the immune defence, but also to adapt to environmental conditions. LPS's structures are highly diversified in the O-specific polysaccharide region to evade bactericidal factors of immune system, but retain some common epitopes that are potential candidates for therapeutic strategies against bacterial infections. Common occurrence of glycine within the structure of L…

Electrospray ion mobility mass spectrometry of positively charged sodium bis[2-ethythexyl)sulfosuccinate aggregates.

2014

Collision cross-sections (CCS) of positively singly and multiply charged aggregates of the surfactant sodium bis(2-ethylhexyl)sulfosuccinate (AOTNa) in the gas phase have been measured by quadrupole ion mobility time-of-flight mass spectrometry. Calibration of the observed drift times to the CCS of the AOTNa non-covalent aggregates was achieved by collecting, under the same experimental conditions, the drift times of a range of singly and multiply charged polyalanine peptides whose CCS had been obtained by conventional ion mobility spectrometry. Together with an obvious increase of the aggregate cross-section with the aggregation number, it was found that the aggregate cross-section increa…