Fast atom bombardment mass spectrometry of salts

The positive and negative fast atom bombrdment spectra of two groups of simple salts have been recorded. The structures of the major ionic species of eight chlorides and five, complex anion, sodium salts have been interpreted and tabulated.     

Fast atom bombardment mass spectrometry of pertechnetate

Negative Ion Fast Atom Bombardment Mass Spectrometry is conducted on potassium pertechnetate evaporated onto a copper probe. The mass spectra of pertechnetate /TcO ₄ ^– / reveal the presence of mononuclear and polynuclear technetium oxo species which form general series Tc_nO _n+1 ^– ,...Tc_nO_n+4 with n=1 to 5. The polynuclear species are believed to be formed via gas phase reactions.     

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.     

Fast atom bombardment and collision-induced dissociation of prostaglandins and thromboxanes: Some examples of charge remote fragmentation

The mass spectra of products found by collisional activation of selected prostaglandins and thromboxanes were studied by tandem mass spectrometry as barium carboxylate salts and as carboxylate anions. Collision-induced dissociation (CID) of these closed shell ions generated by fast atom bombardment mass spectrometry reveals a wealth of structural information for these hydroxy acids. Decomposition reactions were found to be dependent upon the eicosanoid ring structure and the type of ion being studied, either positive or negative ion. The bariated carboxylate salts undergo reactions by processes that are similar to those previously characterized as charge remote mechanisms in which neutral species are lost as in thermal and photolytic decompositions. The most abundant ion is formed by loss of water from each of the hydroxyl groups present on the prostaglandin or thromboxane structure. For these multifunctionalized eicosanoids, typical patterns of decomposition emerge as characteristic of the oxygen substituents present along the carbon chain of the eicosanoid structure. The structural information obtained from the barium salts along with those from the carboxylate anions is substantially different, yet the structural information from each process is complementary. The CIDs of positive ions (metalated salts) provide structural information concerning the substituents between the carboxyl group and C₁₂ of the eicosanoid structure, whereas the decompositions of the carboxylate anions (negative ion mode) provide data concerning structure alterations of the eicosanoid structure between C₁₅ and C₂₀     

Fast atom bombardment mass spectrometry of hydroxybenzoic acids

Summary Ten hydroxybenzoic acids were analysed by positive and negative-ion fast atom bombardment mass spectrometry. FAB-MS of all acids investigated gave intense (M+H)⁺ or (M-H)^– ion peaks. Isomers could be distinguished by the metastabile ion or collisional activation spectra of selected ions, except for m- and p-hydroxybenzoic acid. These compounds could be distinguished, however, by the charge stripping spectra of the (M-H)^– ions.

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FAB-Massenspektrometrie von Hydroxybenzoesäuren

Zusanunenfassung Zehn Hydroxybenzoesäuren wurden mit Hilfe der FAB-Massenspektrometrie (positive und negative Ionen) analysiert. Alle untersuchten Säuren ergaben intensive (M+H)⁺-oder (M–H)^–-Ionenpeaks. Isomere konnten mit Hilfe der Spektren metastabiler Ionen oder von Kollisions-Aktivierungsspektren ausgewahlter Ionen unterschieden werden, außer m- und p-Hydroxybenzoesäure, die durch Charge-stripping-Spektren der (M-H)^–-Ionen unterschieden wurden.

     

Fast atom bombardment mass spectrometry of coordination compounds

It is shown that fast atom bombardment mass spectrometry is well suited for the study of coordination compounds.     

Structural characterization of isoxazolidinyl nucleosides by fast atom bombardment tandem mass spectrometry.

4'-Aza-2',3'-dideoxyerythrofuranosyl derivatives of thymine (AdT, 1) and uracil (AdU, 2) are analogues of 2',3'-dideoxyribofuranosyl thymine (ddT, 3) and uracyl (ddU, 4). Compounds 1 and 2 are representative of a new class of antiviral agents where the sugar moiety is replaced by an isoxazolidine ring. The increasing importance of isoxazolidinyl nucleosides has encouraged the exploitation of simple mass spectrometric rules for unambiguously assigning their structure. The species 1, 2, 5 and 6 were therefore synthesized in order to evaluate the role of the basic centre of the modified sugar moiety in their gas-phase chemistry. The tandem mass spectra of these compounds are similar to those of the wild-type nucleosides and display fragment ions corresponding to [B + 2H](+),[M - BH](+) and [B + 27](+) species, where B is the nucleobase. The last species derives from a retrocycloaddition process which is less evident in 2'-deoxyribosides. This behaviour is consistent with protonation of the analytes at the pyrimidine rings. Model isoxazolidines, in which the nucleobase was replaced by a phenyl or a naphthyl moiety, displayed the expected behaviour of species with a localized charge on the N-O moiety of the isoxazolidine ring.     

Structural characterization of mono- and bisphosphonium salts by fast atom bombardment mass spectrometry and tandem mass spectrometry

Positive-ion fast atom bombardment (FAB) mass spectra are reported for a representative series of mono- and bisphosphonium halides derived from triphenylphosphine. The mass spectra of the monoalkyltriphenylphosphonium salts typically contain abundant intact cations that can be used to establish the cationic relative molecular mass and diagnostic fragment ions that allow the characterization of structural subgroups. Depending on the functional group substitution on the alkyl group, additional fragment ions are observed which are formed by loss of small neutral molecules from the intact cation and that can be used for the differentiation of isomeric phosphonium salts. Molecular dication are typically observed in the FAB mass spectra of the bisphosphonium salts when they are analysed in 3-nitrobenzyl alcohol. In addition, production of singly charged ions by clustering with a counter ion, decomposition involving removal of one of the charge centres and one-electron reduction are generally observed. Structurally diagnostic fragments are also obtained. The fragmentation pathways of the ions derived from the phosphonium salts were elucidated by precursor ion and product ion tandem mass spectrometric experiments. For the phosphonium salts containing a long-chain hydrocarbon alkyl group, high-energy collision-induced decomposition of the intact cation is needed to obtain unambiguous structural information.     

Fast atom bombardment in mass spectrometry: Method and applications

The review article is devoted to the mass spectrometry method of ionization of material by fast atom bombardment (FAB). The FAB method extends the possibilities of mass spectrometry by making it possible to obtain the mass spectra of nonvolatile, thermally unstable, and high-polarity compounds, which contain information on the molecular weight and the structure of the compounds studied. The mechanism of ion formation, the apparatus design, and also the main results of FAB mass spectrometric study of different classes of compounds are examined. This method is specially helpful in analysis of natural compounds.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 23, No. 1, pp. 62–78, January, 1987.     

Fast atom bombardment combined with mass spectrometry for characterization of polycyclic aromatic hydrocarbons

A new approach using fast atom bombardment combined with mass spectrometry to characterize polycyclic aromatic hydrocarbons (PAHs) in the range of 128-252 u molecular weight is described. Sulfolane was employed as a liquid matrix for these π-conjugated hydrocarbons. Bombardment of sulfolane solution of certain PAHs with an atom beam produces both radical cation (M^+.) and protonated molecule [(M + H)⁺], with no evidence of fragmentation. Collisional activation of the fast atom bombardment-desorbed M^+. ions, however, results in several structure-specific fragment ions. Structural differences in a few isomeric hydrocarbons can be detected using the [(M + H)⁺]/[M^+.] abundance ratio and in the pyrene-fluoranthene pair by the B/E linked-field-collision-activated dissociation data. The [(M + H)⁺]/[M^+.] was found to be compound-specific and correlated well with certain properties (resonance energy, proton affinity, and ionizing energy) of PAHs.     

Fast atom bombardment mass spectrometry of two isomeric tripeptides

Fast atom bombardment of solids is presented as the basis of a new ion source for mass spectrometry. This novel technique is particularly useful for obtaining mass spectra from involatile and thermally labile materials. The ion source produces both positive and negative ions with equal facility, and examples of both are presented for two underivatized tripeptides. The normal second field free region metastables are observed in a double focusing mass spectrometer and comprehensive metastable pathways have been traced using Barber-Elliott (V-scan) techniques.     

Novel fragmentation of N-diisopropyloxyphosphoryl dipeptides and tripeptides by fast atom bombardment mass spectrometry

Positive ion fast atom bombardment mass spectrometry of N-diisopropyloxyphosphoryl dipeptides and tripeptides showed a novel cleavage pattern in that only the N-phosphoryl fragment ions gave intense peaks while the C-terminal series of ions was suppressed. The base peak was the N-phosphoryl imino ion responding to the N-terminal residue. These advantages are superior to those of other types of N-protecting groups.     

Fast atom bombardment mass spectrometry of seryl- and O-phosphoseryl-containing peptides

FAB-MS was found to be a mild technique for the rapid identification of O—phosphoseryl residues in peptides and the characterization of O—phosphoseryl—containing peptides.     

Fast atom bombardment mass spectrometry of some alkoxv- and chloro-silanes

The positive and negative FAB mass spectra of a series of alkoxy- and chloro-silanes X_m(CH₃)₃-_mSi(CH₂)_nR [m = 1 or 3, n = 3, 10 or 17, X = Cl or OMe or OEt, R = Me, NH₂, glycidoxy, COOMe, NHCO(CH₂)₇COOMe or NHCO(CH₂)₁₀CH₂OAc] were recorded in NBA and NPOE matrices. The chlorosilanes underwent rapid hydrolysis into silanols which condense to form siloxanes, the process being complete in NBA and partial in NPOE, yielding siloxane-based fragment ions in the positive spectra and silyloxyanions in the negative spectra. The alkoxysilanes were more resistant to hydrolysis, affording abundant [MH – HX]⁺ ions (X = OMe or OEt) in their positive FAB spectra and moderate to high intensity [M – H]^? ions in the negative mode, the latter undergoing characteristic sequential loss of C₂H₄, EtOH and C₂H₄. Significant variations were observed in the positive spectra of all the silanes with change of matrix.     

Fast atom bombardment mass spectrometry of protein and carbohydrate biopolymers

Within the past decade significant advances in the field of biological mass spectrometry have resulted in unique approaches to the structural analysis of biopolymers. This article pinpoints key instrumental developments and outlines strategies based upon high field fast atom bombardment mass spectrometry which are allowing hitherto elusive biopolymer structural data to be obtained.