Mass spectral determination of long-chain quaternary amines in mixtures

The analytical utility of several ionization techniques, which are known for their abilities to produce molecular ions of non-volatile/thermally labile compounds, is compared for the determination of the composition of quaternary ammonium salt mixtures derived from beef tallow. The ionization techniques include direct-exposure chemical ionization, field desorption, and fast atom bombardment. While all three techniques produce molecular cations from the salts, fast atom bombardment produces these in greatest relative abundance. Both fast atom bombardment and direct-exposure chemical ionization can be used for characterization of the composition of chain lengths in the mixture. Fast atom bombardment also produces different fragmentation/decomposition ions (imminium ions) than direct-exposure chemical ionization (protonated tertiary amines).     

Negative-ion electrospray and fast atom bombardment mass spectrometry of esters of boron acids

It is shown that both electrospray and fast atom bombardment mass spectrometry provide excellent negative-ion mass spectra of the anionic esters of boric, boronic and borinic acids. For electrospray, contact of the esters with water causes some hydrolysis but, in most cases, spectra of the intact molecular anions are readily obtained. For fast atom bombardment, solvents that chelate with the boron esters must be avoided, Tetraethylene glycol diethyl ether, pentaethylene glycol dimethyl ether or hexaethylene glycol dimethyl ether are suitable solvents. Negative-ion electrospray mass spectra showed few, if any, fragment ions, whereas fast atom bombardment generally produced abundant M^? ions and several fragment ions of low abundance. It is shown that a simple reaction with dibenzene-borinic acid converts diols such as monoglycerides and monoalkyl glyceryl ethers into anionic borinate esters as a pre-ionization procedure for analysis by electrospray or fast atom bombardment mass spectrometry.     

Analysis of xanthates by negative-ion fast atom bombardment mass spectrometry

A new technique using negative-ion fast atom bombardment mass spectrometry for the analysis of xanthates and related compounds is described. Electron impact and positive-ion fast atom bombardment mass spectrometry produced no structurally related fragment ions or observable molecular ions at the expected m/z values. It was demonstrated that negative-ion fast atom bombardment ionization was the most suitable method of ionization for structure elucidation studies for the compounds described.     

Mass spectrometry of pancuronium bromide and related quaternary ammonium steroids using the moving belt LC/MS interface

Pancuronium and vecuronium are members of a series of quaternary ammonium steroids used as neuromuscular blocking agents in anesthesiology. In this study the mass spectrometric properties of these bromide salts are examined and spectral features which permit their differentiation are evaluated. The relative merits of chemical ionization and fast atom bombardment using the moving belt liquid chromatography/mass spectrometry interface have been investigated. Fragmentation pathways for both ionization methods were determined with deuterium labeling and linked-scan techniques. Cleaner spectra can be obtained via the matrix-free belt introduction system as compared to conventional fast atom bombardment.     

Evidence that gas-phase ion-molecule reactions are responsible for the behaviour of crown ethers under fast atom bombardment conditions

The fast atom bombardment mass spectrometry of some crown ethers shows the formation of both [M + H]⁺ and [M ? H]⁺ ions, paralleling behaviour already observed using electron impact ionization. The study of these oily samples with and without a glycerol matrix, trifluoroacetic acid or alkali metal salts, suggests that the ionization process does not occur in the condensed phase, but in the selvedge region by gas-phase ion-molecule reactions in accordance with the ‘gas-phase explosion model’. Positive-ion chemical ionization experiments support this proposal.     

Fragment ion formation of quaternary ammonium salts under fast atom bombardment and field desorption collisionally activated dissociation conditions

Comparing fast atom bombardment and field desorption collisionally activated dissociation mass spectra of tetrabutyl ammonium salts it becomes evident that under fast atom bombardment conditions, besides desorption of intact salt cations, the ionization of intact salt molecules must be assumed. Alkyl ions formed under fast atom bombardment and not under field desorption collisionally activated dissociation conditions are ionization products of tetraalkyl ammonium salt molecules. Radical cations are produced by both techniques.     

Fast atom bombardment mass spectra of isobaric/isomeric phosphonium salts

The positive ion fast atom bombardment mass spectra of isobaric/isomeric aryl phosphonium salts typically contain abundant intact cations, which can be used to establish the cationic molecular weight, characteristic ions that can be used to delineate structural subgroups, and fragment ions corresponding to losses of small neutral molecules. Several of the fragmentation pathways were elucidated by parent ion and daughter ion tandem mass spectrometry experiments. Dependence of the fragmentation reactions on functional group substitution suggests that fast atom bombardment mass spectrometry is an excellent method for the differentiation of isobaric/isomeric phosphonium salts used in synthetic organic and industrial catalytic processes.     

Ionization by fast atom bombardment—A chemical lonization (matrix) process in the gas phase?1

It is proposed that ion formation from non-ionic substrates under fast atom bombardment occurs essentially by chemical ionization in the gas phase by a matrix plasma. Corroborating experiments regarding the matrix plasma are presented.     

The fast atom bombardment mass spectra of furyl and thienyl silanes and germanes in comparison with their electron impact mass spectra

The interaction of the π electron system of furyl and thienyl substituents with the silicon (or germanium) atom is less significant in fragmentation under fast atom bombardment than under electron impact. Under fast atom bombardment the primary fragmentation of the title compounds is determined by steric influence of the heteroaromatic substituents.     

The fast atom bombardment mass spectra of glucosinolates and glucosinolate mixtures

The behaviour of glucosinolates and desulphoglucosinolates under fast atom bombardment conditions has been investigated. Relatively little fragmentation was noted in the mass spectra of these compounds. The positive ion fast atom bombardment mass spectra of glucosinolates exhibited abundant cationized and protonated molecula ions, thus complementing the previously reported electron impact and chemical ionization mass spectra of these compounds. Desulphoglucosinolates yield only the protonated molecular ion. Under negative ion conditions the spectra of glucosinolates were dominated by the molecular anion and this has been used as a means of analysing a crude plant extract containing a complex mixture of glucosinolates.     

Comparative EI,CI and FAB Mass Spectrometry of Dialkyl and Monoalkyl 2-Chloroethylphosphonates

Abstract

Comparison is made between electron ionization (EI), methane, isobutane and ammonia chemical ionization (CI) and fast atom bombardment (FAB) mass spectrometry of phosphonates related to 2-chloroethylphosphonic acid     

Characteristic fragmentations of peptide derivatives containing proline in negative-ion fast atom bombardment mass spectrometry

Fragmentations of N-benzyloxycarbonyl-protected tripeptide ethyl esters containing proline were compared with those of the corresponding peptide derivatives not containing proline in negative-ion fast atom bombardment mass spectrometry. The fragment ion [M – 109]^? due to loss of the benzyloxy group followed by dehydrogenation from the peptide molecule was the base peak in the negative-ion mass spectra for the peptides not containing proline, whilst it was a very weak fragment ion or not observed at all in those for the peptides containing proline. These results suggest that the fragmentations of the peptide derivatives in negative-ion fast atom bombardment mass spectrometry depend on the conformational difference of the peptide derivatives owing to the existence of proline in the derivative.     

Applicability of high-performance liquid chromatography--continuous-flow fast atom bombardment mass spectrometry for simultaneous quantitation of multiple neurochemicals.

A method is described for the analysis of multiple neurochemically important compounds. The technique involves high-performance liquid chromatographic separation in combination with ultraviolet and continuous-flow fast atom bombardment mass spectrometric detection. High-performance liquid chromatographic elution behaviour and relative detection responsiveness as correlated with chemical structure are also presented.     

质谱技术在糖类结构分析中的应用

综述了电子轰击、化学电离、快原子轰击、电喷雾离子化、基质辅助激光解吸、串联质谱等质谱技术在糖类结构分析中的应用。引用文献共53篇。     

Synthesis and properties of new fluorenonocrownophanes having a stilbene fragment and their reaction with paraquat

New crownophanes containing 2,7-dioxyfluorenone and 4,4??-dioxystilbene fragments linked through di-, three, tetra-, and pentaethylene glycol linkers were synthesized. The formation of pseudorotaxanetype host-guest complexes in reactions of these crownophanes with 1,1??-dimethyl-4,4??-bipyridinium dication was detected by fast atom bombardment mass spectrometry, ¹H NMR, and electron spectroscopy.     

A rapid mass spectrometric strategy suitable for the investigation of glycan alterations in knockout mice

A method for the rapid screening of mouse tissues using fast atom bombardment mass spectrometry in combination with linkage analysis and specific enzymatic and chemical digests is described. This strategy has been successfully employed in the analysis of a wide range of murine organs and data from brain, kidney and lung tissue are presented.     

Fast atom bombardment mass spectrometry of polyglycols

Fast atom bombardment mass spectrometry (FAB-MS) has rapidly become established, after its introduction two years ago, as a method of choice for mass spectral analysis of higher molecular weight polar organic chemicals. In industrial analysis, the technique has been found to be a very effective method for analyzing numerous classes of polar polymeric chemicals, including rubber and plastic additives, organometallics, and polar polymers. Normally applied in conjunction with field desorption (FD-MS), FAB-MS is used to determine chemical structures for both pure compounds and oligomeric mixtures. Fast atom bombardment results for poly(ethylene glycol) and poly(propylene glycol) show that, while oligomer quasimolecular ion distributions give a rough indication of relative oligomer abundances, the data are not quantitative in comparison with that previously described for FD-MS (or electrohydrodynamic ionization, EH-MS) analysis. More specifically, lower mass oligomer intensities tend to be too high in FAB-MS due to fragmentation reactions.     

Differentiation of diastereomeric chlorin derivatives by fast atom bombardment mass spectrometry

The stereochemistry of six pairs of diastereomeric chlorin derivatives was investigated by electron impact (EI), fast atom bombardment (FAB) and direct chemical ionization DCI mass spectrometry. It was demonstrated that FAB and EI mass spectrometry are convenient and rapid methods for distinguishing between diastereomeric chlorin derivatives due to their different fragmentation patterns.     

Evaluation of thin layer chromatography—Fast atom bombardment mass spectrometry: Application to the determination of midazolam intoxication by use of 3-glycidoxypropyl-treated thin layer chromatographic plates

Summary The effectiveness of 3-glycidoxypropyl-treated thin layer chromatographic plates in the determination of midazolam intoxication has been studied by thin layer chromatography/fast atom bombardment mass spectrometry. Silica plates treated with 3-glycidoxypropyldimethylethoxysilane were used for the measurement of their physical composition and for chemical analysis. From elemental carbon analysis data, the maximum number of bonded 3-glycidoxypropyl surface groups per gram was calculated to be 0.417×10²¹. Midazolam in human serum from patients suffering from intoxication could be separated on a 3-glycidoxypropyl-treated thin layer chromatographic plate with chloroform as eluent. After applying the technique of diffused spot condensation on the 3-glycidoxypropyl-treated thin layer chromatographic plate, the established thin layer chromatography/fast atom bombardment mass spectrometry method was used for the identification of midazolam intoxication, and improved the detection limit for midazolam in the serum of an intoxication patient by 30 times.     

Contribution of mass spectrometric techniques to the structure elucidation of antibiotic GE2270A,a novel inhibitor of bacterial protein synthesis

GE2270A is a novel antibiotic active against Gram-positive bacteria and anaerobes. Its structure originates from a peptidic backbone, the amino acids of which have been modified to produce a macrocycle and a side-chain. It contains a heterocyclic chrornophonc system, a number of thiazoleamino acids and three unmodified natural amino acids. The structure [relative molecular mass (RMM) 1289] was determined using various spectroscopic techniques, of which fast atom bombardment mess spectrometry, gas chromatography/mass spectrometry, desorption chemical ionization mass spectrometry and fast atom bombardment tandem mass spectrometry played an important role. The mass spectrometric approach was applied to the intact molecule and to the various hydrolysis products, including the chromophoric part (RMM 634).