Parent Ion Peak Research Articles

The Analysis of Conducting Polymers by Electrospray Fourier Transform Mass Spectrometry. Part I: Ionene Polymers

The analysis of synthetic 6-2, 6-3 and 6-4 ionene polymers by electrospray ionization Fourier transform mass spectrometry (ESIFTMS) is reported here. This is the first in a series of papers on the analysis of conducting polymers utilizing soft ionization techniques, thus allowing for the analysis of intact molecular ions. The syntheses of these individual polymers result in a variety of compounds with different molecular structures which are related to the normal linear ionene polymer. While the mechanisms by which the 6-2 and the 6-3 ionene polymers are synthesized are very similar, the synthesis of 6-4 ionene proceeds differently. In addition, the presence of a gas-phase bromide ion salt-bridged to the backbone of the polymer chain is observed in the resulting mass spectra, as well as the possibility of intramolecular cyclization. The latter has been proposed previously. This cyclization process becomes more possible as the number of methylene groups in the linking chain increases. Finally, we observed that the presence of a bromide ion in the sample helped the interpretation of sustained off-resonance irradiation collisionally-activated dissociation (SORI-CAD). Based on the isotopic pattern provided by the halogens, a “built-in” label which can be traced from the fragment ions back to the parent ion peak is found to be useful in structural assignments.

Synthesis and Characterization of Rhenium(III) and Technetium(III) Organohydrazide Chelate Complexes. Reactions of 2-Hydrazinopyridine with Complexes of Rhenium and Technetium.

The organohydrazide chelate complexes M(III)(NNpy)(PPh(3))(2)Cl(2) (1, 3) (M = Re, Tc) have been synthesized using the organohydrazine 2-hydrazinopyridine. The chelated organohydrazide is a diazenido(1-) ligand that forms a five-membered ring with the metal center. An X-ray structural analysis of 1 indicates that there is a delocalized pi-system formed by the chelate ring. These octahedral, d(4) metal complexes have diamagnetic (1)H NMR spectra. Complex 1, C(41.50)H(34)Cl(2)N(3)O(0.5)P(2)Re, crystallizes in the triclinic space group P&onemacr; with a = 10.5549(7) Å, b = 12.2699(8) Å, c = 16.8206(12) Å, alpha = 105.9050(10) degrees, beta = 95.8930(10) degrees, gamma = 111.0100(10) degrees, V = 1906.1(2) Å(3), Z = 2, and R = 0.0650 based on 5268 unique reflections. The FABMS+ in (p-nitrobenzyl alcohol) of 3 reveals a parent ion peak at m/z 799.2. The complex [Re(HNNpy)(NNpy)(PMe(2)Ph)(2)Cl](+)[Cl](-) (2) contains a chelated, neutral organodiazene ligand and a linear, diazenido(1-) ligand. The X-ray structural analysis of 2, C(26)H(30)Cl(2)N(6)P(2)Re, indicates a delocalized pi-system formed by the chelate ring. The (1)H NMR spectrum of 2 is not paramagnetically shifted. Complex 2 crystallizes in the orthorhombic space group Pna2(1) with a = 17.383(4) Å, b = 13.967(3) Å, c = 12.002(2) Å, V = 2913.9(10) Å(3), Z = 4, and R = 0.0384 based on 3083 unique reflections.

Sensitive capillary gas chromatographic-mass spectrometric-selected-ion monitoring method for the determination of diclofenac concentrations in human plasma.

We have modified and validated a capillary GC-MS method reported by Kadowaki et al. [J. Chromatogr., 308 (1984) 329] for the determination of diclofenac in human plasma by using heptane rather than benzene as an extraction agent. In addition, acetone was added to the samples as a deproteination agent which increased the recovery of diclofenac. These revised processes allowed clean extraction and near-quantitative recovery of analyte (> 95%). Separation was achieved on an HP-1 column with helium as carrier gas. The parent ion peaks of diclofenac (m/z 277) and the internal standard, 4'-methoxydiclofenac (m/z 307), were monitored by a mass-selective detector using the selected-ion monitoring mode. The linear range for the routine assay was from 5 to 2000 ng/ml. The detection and lower quantifiable limits were 0.2 and 1 ng/ml, respectively, with no interference from plasma. The within-day and between-day coefficients of variation for high and medium concentrations were less than 5% and were less than 13% for low concentrations (10 ng/ml). This GC-MS assay method has been used for pharmacokinetic and drug interaction studies in humans.

Sunlight induced synthesis of tricarbonylhexahaptobuckminsterfullerenetungsten

[W(CO)3(η 6-C60)] has been synthesized by sunlight irradiation of a benzene solution of C60 and W(CO)6 or [W(CO)3(η 6-C6H6)] as a red-brown solid. This compound has been characterized by elemental analysis and by FAB mass spectroscopy (parent ion peak centred at 988 (30%)). Chemical reactivity and IR spectroscopy indicate a hexahapto mode of bonding in this complex according to the 18-electron rule. XPS and cyclic voltammetric data support the electron acceptor/donor properties of bonded C60 and the electron donor/acceptor properties of W(CO)3 moiety respectively in this compound.

A Novel Type of Protein Modification by Isoprenoid-derived Materials. DIPHYTANYLGLYCERYLATED PROTEINS IN HALOBACTERIA

Previous work from this laboratory has shown that a derivative of [3H]mevalonic acid is incorporated into a number of specific proteins in Halobacterium halobium and Halobacterium cutirubrum and that the major radioactive material released by treatment with methyl iodide was neither farnesyl nor geranylgeranyl compound, which have been generally accepted to be prenyl groups of a number of prenylated proteins found in eukaryotic cells, but an unknown compound (Sagami, H., Kikuchi, A., and Ogura, K. (1994) Biochem. Biophys. Res. Commun. 203, 972-978). In the current study, the unknown compound was prepared in a large amount from H. halobium cells and analyzed by reverse and normal phase high performance liquid chromatographies followed by mass spectrometry. The mass spectrum of this compound exhibited a parent ion peak (M+) at m/z 682, suggesting that it is a 1-methylthio-2,3-di-O-(3',7',11',15'-tetramethylhexadecyl)glycerol (diphytanylglyceryl methylthioether). Diphytanylglyceryl methyl thioether was chemically synthesized, and its mass fragmentation pattern was completely coincident with that of the mevalonic acid-derived material from H. halobium. These results indicate that Halobacteria contains specific proteins with a novel type of modification of a cysteine residue of the proteins with a diphytanylglyceryl group in thioether linkage.

A mechanism for the rearrangement of unsymmetrical tetradentate (N2O2) ligands bound to manganese(III): the isolation and crystal structure of a manganese(III) complex containing a ten-membered cis-chelated ring

The unsymmetrical Schiff-base ligand L1(where H2L1 is the condensation product of 8-amino-4-methyl-5-azaoct-3-en-2-one and 3-ethoxysalicylaldehyde) has been found to rearrange into the symmetrical ligand L2[H2L2=N,N′-bis(3-ethoxysalicylidene)propane-1,3-diamine] in the presence of manganese(III). The manganese(III) complexes of both the unsymmetrical and symmetrical ligands have been characterised by elemental analyses, infrared spectroscopy, magnetic susceptibility measurements and fast atom bombardment (FAB) mass spectrometry and have been assigned the stoichiometries [Mn(HL1)2][ClO4]·H2O and [MnL2][ClO4]·3H2O based on these data. The FAB mass spectrum of the former exhibits an interesting phenomenon, with two distinct metal co-ordination environments being observed. The ion of [Mn(HL1)2]+ at m/z 661 is observed, as would be expected from the experimental data; however, the parent ion peak at m/z 357 corresponds to the monomeric [ML1]+ ion with the amine nitrogen atom of the ligand deprotonated. The manganese(III) complex of the unsymmetrical ligand [Mn(HL1)2][ClO4] has been crystallographically characterised, no water of crystallisation being observed in the selected crystal. This monomeric complex consists of a pseudo-octahedral metal centre with an N2O4 donor environment. The non-co-ordination of the amine nitrogen atom, confirmed by the Mn ⋯ N(2) separation of 3.51 A, produces a ten-membered chelate ring about the manganese ion, believed to be the first example of such a system. The crystal structure has enabled a mechanism for the rearrangement of Schiff bases about manganese(III) to be proposed. It involves a series of reversible hydrolysis reactions which are stabilised by manganese(III) acting as a template.

Photoionization mass spectrometric study of CH3OF

The vacuum ultraviolet photoionization mass spectrum of CH3OF displays a prominent parent ion peak, whose adiabatic onset is 11.340±0.008 eV, although much lower energy fragmentation processes (CH2O++HF, 8.0 eV; CH2OH++F, 9.3 eV) are possible. These lower energy processes have very low intensity. Two higher energy processes, to CH+3+OF and CH2O++H+F, are observed. Their thresholds are used to determine ΔH0f0 (CH3OF)≥−23.0±0.7 kcal/mol, or D0 (CH3O–F)≤47.4±1.2 kcal/mol. CH2OF+ is a significant fragment, whose appearance energy leads to ΔH0f0 (CH2OF+)≊215.1±0.8 kcal/mol.

New mass spectrometric data to aid etching and growth studies of GaAs using As and Ga trichlorides

We have made new measurements of the mass spectra of AsCl 3 and GaCl 3 as an aid to researchers investigating the interaction of chlorine with GaAs surfaces. We have found the dominant feature in the spectrum of both materials to be the dichloride ion. Also, the parent ion peak is larger for AsCl 3 while GaCl 3 shows more cracking to GaCl + and Ga +, and significant amounts of the Ga 2Cl + 5 ion.

Mechanism of formation of the putative advanced glycosylation end product and protein cross-link 2-(2-furoyl)-4(5)-(2-furanyl)-1H-imidazole.

2-(2-Furoyl)-4(5)-(2-furanyl)-1H-imidazole (FFI) is a fluorescent molecule which was originally discovered in chloroform extract of ammoniacal solution of acid-hydrolyzed glycated proteins and proposed to represent a protein cross-link. The absence of a lysyl residue side chain and other observations promoted a detailed study of its mechanism of formation. Glycated alpha-t-Butoxycarbonyllysine was incubated for 29 days and periodically assayed for FFI and FFI-like fluorescence. Whereas fluorescence increased over time, FFI recovery was unexpectedly highest on day 0 and lowest on day 29, suggesting that FFI was directly derived from Amadori products. FFI was also recovered from hydrolysates of glycated neopentylamine, furosine, and browned poly-L-lysine but was virtually undetectable in similar solutions basified with NaOH, triethylamine, or pyridine instead of ammonia. Gas chromatography-mass spectrometry analysis of FFI from similar hydrolysates basified in the presence of 15N-enriched NH4Cl revealed for all precursors a parent ion peak at 230 instead of 228 m/e units, suggesting that the two imidazole nitrogen atoms had been incorporated from free ammonia into FFI. Spontaneous FFI synthesis occurred when furosine was reacted with aqueous ammonia at room temperature. These results do not support the proposition that FFI is an advanced glycosylation end product or a protein cross-link. They suggest that FFI is formed from ammonia and furosine which are by-products of acid-hydrolyzed glycated proteins.

Application of Two-Step Laser Mass Spectrometry to Cosmogeochemistry: Direct Analysis of Meteorites

Polycyclic aromatic hydrocarbons in C1, C2, and C3 carbonaceous chondrites and in some ordinary chondrites have been directly analyzed by two-step laser desorption/ laser multiphoton ionization mass spectrometry, a selective and sensitive method requiring only milligram samples. At the ionization wavelength of 266 nanometers, parent ion peaks of polycyclic aromatic hydrocarbons dominate the mass spectra. Quantitative analysis is possible; as an example, the concentration of phenanthrene in the Murchison meteorite was determined to be 5.0 parts per million.

Determination of phenylthiohydantoin-amino acids by two-step laser desorption/multiphoton ionization.

The 20 primary phenyithlohydantoln (PTH)-amino acids can be detected and quantltated by time-of-flight (TOF) mass spectrometry using a two-step laser methodology. First a CO, laser pulse desorbs the PTH-amlno acid or a mlxture thereof prepared as a thin film on the Inside wall of a rotating glass cup. The latter Is part of the first electrode of the TOF apparatus. The desorptlon process Is demonstrated to be essentlaity complete In the laser spot area. After a dah the delay, a second UV laser pulse (266 nm) causes 1 + 1 resonance-enhanced multiphoton ionization (REMPI) of the neutral cloud of desorbed molecules. The mass spectra obtained are domlnated by the parent Ion peak In almost all cases. Knowledge of the velocity dlstrlbutlon permlts flux measurement. The ion slgnai is linear in PTH-amino acid concentration in the range of picomoles io nanomoles. This Is the fhst demonstration of quantltative analysls of molecules by laser desorptlon/multlphoton Ionization.

Fission fragment ionization mass spectrometry: Metastable decompositions

Distorted peak shapes observed in 252Cf fission fragment ionization mass spectrometry using time-of-flight mass spectrometers are shown to result from delayed dissociations of initial ions. Decompositions occurring in the ion acceleration region produce tails on parent or fragment ion peaks, and decompositions occurring with the conversion of internal to kinetic energy in the field-free ion drift region produce broadenings of the parent ion peaks. In this work the various processes have been investigated by the application of appropriate retarding potentials. Examples of the various decomposition processes are given. The magnitudes of the internal energies converted are given for several processes. The application of suitable retarding potentials can be used to suppress decomposition products and enhance resolution and to determine the identities of the decomposition processes.

Mass Spectrometric Study of the Primary Processes in Photochemical Reactions. II. Mass Spectra of Methyl and Ethyl Radicals

Abstract The mass spectra of methyl and ethyl radicals have been determined by the photolyses of methyl and ethyl iodide using a high intensity light beam and a collision-free photochemical reactor incorporated in the ion-source of a mass spectrometer. The parent ion peak was the most intense in the mass spectra of methyl and of ethyl radicals. Fair agreement was found between the present work and the result obtained by previous workers for pyrolytically produced methyl radicals.

A mass spectrometric study of some monocyclic polycarbonyl compounds

The mass spectra of squaric acid, croconic acid, rhodizonic acid, and of their oxidation products octahydroxycyclobutane, leuconic acid, triquinoyl, and also of the related compound tetra-hydroxy- p-benzoquinone have been studied. Characteristic features of the fragmentation of all these molecules are the elimination of carbon monoxide and ring contraction. The spectra of the acids show appropriate parent ion peaks, their oxidation products do not show parent ion peaks either of the fully hydrated or the fully dehydrated molecules.

Observation of the Products of Ionic Collision Processes and Ion Decomposition in a Linear, Pulsed Time-of-Flight Mass Spectrometer

A retarding potential technique has been investigated which permits study of secondary processes occurring after ion acceleration in a time-of-flight mass spectrometer. By application of a retarding field near the end of the flight path, peaks due to neutral species and fragment ions formed after acceleration are separated from their parent ion peaks and displayed in the same panoramic mass spectrum. Charge exchange, collision-induced dissociation, and spontaneous (metastable) ion decomposition are easily observed. The identities of initial ions and fragment ions involved in secondary processes can be determined unambiguously without complications of peak overlap.

Dimer acid structures. The dehydro‐dimer from methyl stearate and di‐tertiary‐butyl peroxide

AbstractPrevious work by Sutton, and by Harrison, McCaleb and Wheeler has shown that methyl stearate is converted to dimers plus higher polymers by the action of di‐t‐butyl peroxide. The latter suggested that in the dimer, there was considerable linkage at carbon 2, the carbon ॅ‐ to the COOCH3 group, since the dimer ester was incompletely saponified by the usual procedures.Further proof of ॅ‐linkage is now presented. A fraction which is predominantly ॅ‐,ॅ艂‐linked dimer was isolated as the nonpolymeric cyclic anhydride (ॅ‐,ॅ艂‐dicetyl succinic anhydride) by molecular distillation from the linear polymeric non‐ॅ‐linked polyanhydride. The isolated cyclic anhydride appeared identical with a synthetic ॅ‐,ॅ艂‐dicetyl succinic anhydride, whose synthesis is described.The original dimer ester, the ॅ‐,ॅ艂‐cyclic anhydride fraction, and the dimethyl ester derived from it, were examined by mass spectrometry. The expected mol wt were confirmed by the parent ion peaks. Fragmentation patterns indicated appreciable ॅ‐linkage in the original dimer ester, and almost exclusive ॅ‐linkage in the ester from the isolated cyclic anhydride. Aside from preference for the ॅ‐position, joining appears to be randomly distributed.