Ammonia Chemical Ionization Mass Spectra Research Articles

Gas chromatographic-mass spectrometric investigation of dextromoramide (palfium) metabolism in the horse

Dextromoramide (Palfium) was given by intravenous injection to a Thoroughbred horse at a dosage of 20 mg and urine was collected 2, 4, 6 and 8 h after drug administration. Enzymatic hydrolysis of the urine followed by solvent extraction gave a residue which was back-extracted into 0.1 M sulphuric acid. After basification to pH 9 and solvent extraction, the resulting residue was submitted to gas chromatographic—mass spectrometric analysis. Both electron-impact and ammonia chemical-ionization mass spectra were recorded and, based on the observed fragmentation patterns, the principal metabolites in horse urine were shown to be 2,2-diphenyl-3-methyl-4-morpholinobutyramide (compound 2) and the product of hydroxylation of one phenyl ring in dextromoramide (compound 3), respectively. The electron-impact mass spectra of compounds 2 and 3, and of their derivatisation products from on column methylation in the gas chromatograph, are reported.

Sites of protonation in phenothiazines: Methane and ammonia chemical ionization mass spectra

AbstractPositive ion methane and ammonia chemical ionization mass spectra for ten phenothiazine derivatives are reported. The fragmentations observed in the chemical ionization mass spectra are rationalized in terms of the location of the added proton. High‐resolution measurements are used to confirm empirical formulae of the ions in the mass spectra. Changes in the mass spectra with a change in the chemical ionization reagent gas from methane to ammonia are described. A comparison with positive ion secondary ion mass spectra of the same compounds show that the amount of fragmentation is higher in the secondary ion mass spectra, but the same types of ions are observed in spectra produced by both ionization methods.

Electron impact and chemical ionization mass spectra of some tetra‐acetylated anomeric glycosides

AbstractElectron impact and chemical ionization (CH4, iso‐C4H10 and NH3) mass spectra of some tetra‐acetylated anomeric glycosides have been examined with a view to the characterization of anomeric pairs. Minor differences observed in the relative intensities of common ions in the anomeric pairs in the electron impact mass spectra are found to be enhanced in the methane and isobutane chemical ionization mass spectra. In the absence of thermal decomposition, the β‐anomers show greater ion abundances of common glycosyl ions than the α‐anomers. Ammonia chemical ionization mass spectra show complementary behaviour indicating strong adduct ions and practically no fragmentation.

Electron impact and chemical ionization mass spectra of nitro‐substituted polyfunctional isomers

AbstractThe electron impact and methane and ammonia chemical ionization mass spectra of some selected nitro‐substituted isomeric benzalacetophenones, benzyl ketones and aromatic epoxides have been examined. The isomeric pairs show significant differences in the electron impact and chemical ionization spectra. The EI spectra show cleavage α to the carbonyl as the major fragmentation mode. Under CI conditions subtle differences in the fragmentation modes of isomeric pairs are more enhanced, and elimination reactions are more favoured in the o‐nitro‐substituted compounds than in the para isomers.

Ammonia chemical ionization mass spectra of esters and amides of oxyacids of phosphorus

AbstractChemical ionization mass spectrometry using ammonia as the reagent gas has been carried out with esters and amides of a variety of oxyacids of phosphorus (phosphates, phosphonates, phosphites and phosphoramidates). In all cases, the protonated molecular ion is a major species in the spectrum and the percentage of the total ion current carried by these protonated molecular ions is always considerably greater than that carried by the molecular ions in the corresponding electron impact mass spectra. In the chemical ionization mass spectra only limited fragmentation of the protonated molecular ion occurs from which useful information on the structure of phosphorus derivatives may be inferred.

Some aspects of chemical ionization mass spectrometry using ammonia, diethylamine and various other reactant gases.

Substitution reactions between ammonia and several simple aromatic compounds containing good leaving groups have been studied with the use of d 3-ammonia as an aid to the analysis of the ammonia chemical ionization mass spectra. The use of several chemical ionization reactant gases introduced via the septum inlet of the VG 70-70 mass spectrometer is described, particularly the use of diethylamine for the molecular weight determination of trityl compounds.

Ammonium adduct ion in ammonia chemical ionization mass spectrometry. Formation of adduct ion.

The mechanism of formation of ammonium adduct ion, [M+NH4]+, observed in ammonia chemical ionization mass spectra, was examined by using a selected set of compounds. It was found that the adduct ion is formed preferentially when the proton affinity of the substrate molecule is close to that of ammonia.

The quantitative analysis of indole glucosinolates by gas chromatography — the importance of the derivatisation conditions

AbstractThe effect of derivatisation conditions on the quantitative analysis of indole glucosinolates as the desulphated trimethylsilyl derivatives using gas chromatography is examined. Structures for the trimethylsilyl derivatives of glucobrassicin and neoglucobrassicin are suggested from an analysis of their ammonia chemical ionisation mass spectra. Caution is urged in the analysis of these compounds without prior optimisation of the conditions of derivatisation.

Dimeric epoxy fatty acid methyl esters: formation, chromatography and mass spectrometry

The formation of dimers is reported from the thermal treatment of a series of epoxy fatty acid methyl esters. These compounds were isolated from the reaction mixture by steric exclusion chromatography and were subsequently characterised by their high resolution electron impact and ammonia chemical ionisation mass spectra. The spectra were consistent in each case with the presence of a mixture of four possible positional isomers each containing an ether bridge linking a pair of fatty acid methyl esters across the carbon chains, with a keto group on a carbon adjacent to the bridge on one of the esters.

Ammonia gas: an improved reagent for chemical ionization mass spectrometry of bile acid methyl ester acetates

The ammonia chemical ionization mass spectra of 28 methyl ester acetate derivatives of bile acids and related compounds have been determined by gas-liquid chromatography-mass spectrometry. Advantages of ammonia ionization over the previously studied isobutane ionization include a 130-270% enhancement in the sensitivity of base peak monitoring, and direct determination of molecular weight from the base peak (M + NH4+) in the mass spectrum of any of the derivatives. Minor ions in the ammonia spectra also allow selective detection of 3-keto compounds and can indicate unsaturation or double bond conjugation in the molecule. The significance of these studies for the detection and quantitation of bile acids is discussed.

Analysis of fatty acid methyl esters by high-resolution gas chromatography-chemical ionisation mass spectrometry

The potential of support-coated open tubular gas chromatography combined with chemical ionisation mass spectrometry using NH 3, CH 4 and He as reactant gases in the analysis of fatty acid methylesters (FAME) has been investigated. Differentiation between unsaturated FAME and cyclopropane FAME could be made on the basis of retention time and by comparison of the chromatograms obtained using methane and ammonia chemical ionisation. The ammonia chemical ionisation mass spectra of FAME, with the exception of 3-hydroxy-FAME, contained only the [M + NH 4] + adduction. The helium chemical ionisation mass spectra of branched chain FAME were qualitatively similar to reported electron impact mass spectra and enabled the point of branching to be determined.

Cardenolide analogues: 10--characterization of cardiac glycosides by chemical ionization mass spectrometry.

The potential of chemical ionization mass spectrometry for the characterization of naturally occurring and semi-synthetic cardiac glycosides has been investigated. Methane, isobutane and ammonia were used as reactant gases. With the exception of ouabain, the ammonia chemical ionization mass spectra of the cardiac glycosides examined in this work contained abundant [M + NH4]+ions and abundant fragment ions formed by cleavage of glycoside bonds. Ammonia chemical ionization mass spectrometry was found to provide a rapid and sensitive method for the characterization of the products of glycosidation reactions. In contrast, the methane and isobutane chemical ionization mass spectra of the cardiac glycosides, with the exception of ouabain, did not contain protonated molecular ions and did not contain abundant fragment ions above m/z 400.

Ammonia chemical ionization of some free amino acids and underivatized peptides

Ammonia chemical ionization mass spectra of rapidly heated free amino acids and peptides provide an opportunity for a study of the competition between gas-phase solvation and association reactions of these biochemically interesting species. Compounds investigated include methionine, phenylalanine, tryptophan, and peptides; AlaAla, PheAla, AlaAlaAla, AlaPheGly, GlyAlaPhe, tetraAla and PCAHisProNH 2 (thyrotropin releasing hormone). Extensive formation of solvated-protonated species were observed and associated protonated peptides up to (4 M + 1) + in some cases. The observation of association reactions with rapidly heated samples presents problems in the analytical use of this technique. Investigation of the kinetic order of reactions leading to association of protonated species reveals a significantly more effective energy transfer process in collisions of protonated peptides with parent neutral molecules than with neutral solvent gas.

Synthesis and characterization of glucuronides of Cannabinol, cannabidiol, delta9-tetrahydrocannabinol and delta8-tetrahydrocannabinol.

Partially purified glucuronyltransferase immobilized on beaded sepharose has been used to synthesize the glucuronide conjugates of cannabinol, cannabidol, delta9-tetrahydrocannabinol and delta8-tetrahydrocannabinol. Trimethylsilylated methyl esters and per(trimethylsilyl) derivatives of these conjugates have been characterized by their gas chromatographic retention times and their electron impact and ammonia chemical ionization mass spectra.