Composition of hydrofullerene mixtures produced by C(60) reaction with hydrogen gas revealed by high-resolution mass spectrometry

Complex solid hydrofulleride mixtures were synthesized by prolonged hydrogenation of C(60) at 120 bar hydrogen pressure, 673 K temperature, and different reaction periods. The high degree of hydrogenation was confirmed by infrared spectroscopy and X-ray diffraction. The identity of hydrogenation products was determined by high-resolution field desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry. Despite partial gas-phase fragmentation of hydrofullerene ions during mass analysis, the data suggest that the synthesized mixtures consist of mostly C(58-60)H(x) hydrofullerenes. Increasing the duration of hydrogenation results in synthesis of C(59)H(x) and C(58)H(x) as major products. Possible hydrofullerene fragmentation pathways during both material synthesis and mass spectrometric analysis are discussed. Gas-phase fragmentation in the mass spectrometer arises from hydrofullerene ions C(60)H(x)(+) with x > 40 and C(59)H(44)(+) with drastically decreased molecular stability relative to the known C(60)H(36).     

Evaluation of Quantitative Sulfur Speciation in Gas Oils by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry: Validation by Comprehensive Two-Dimensional Gas Chromatography

Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) has been applied for the quantitative speciation of sulfur containing compounds in gas oil (GO). For this purpose, ionization and mass spectrometric parameters have been studied and optimized with a set of standard compounds and GO samples. Comprehensive two-dimensional gas chromatography (GCxGC) was used as the reference method. To allow a quantitative comparison between FT-ICR MS and GCxGC results for GO samples, FT-ICR MS parameters were optimized and data obtained by both techniques were standardized. Response factors were established for two ionization modes: atmospheric pressure photo ionization (APPI) and electrospray after selective derivatization of sulfur compounds (MeESI). To test the validity of the developed MS methods, a third GO was analyzed and response factors were applied. Comparison with GCxGC results showed good agreement for sulfur families (deviation within 5% and 15% for MeESI and APPI data, respectively). Abundances of individual isomer groups match within 40% in most cases. These results principally demonstrate the suitability of FT-ICR MS for a quantitative analysis of sulfur compounds (by DBE and carbon number distribution pattern) in petroleum middle distillates. This approach has the potential to be extended to higher- and non-boiling petroleum fractions where quantitative speciation is presently not available.     

Organic environments on Saturn’s moon,Titan: Simulating chemical reactions and analyzing products by FT-ICR and ion-trap mass spectrometry

Laboratory simulations have been carried out to model chemical reactions that possibly take place in the stratosphere of Saturn's moon, Titan. The aerosol products of these reactions (tholin samples) have been systematically analyzed by mass spectrometry using electrospray ionization (ESI) and laser desorption (LD). A wide variety of ions with a general formula C(x)H(y)N(z) detected by ultrahigh resolution and accurate mass measurements in a Fourier transform/ion cyclotron resonance (FT-ICR) cell reflect the complexity of these polymeric products, both in chemical compositions and isomeric distributions. As a common feature, however, tandem mass spectral (MS/MS) data and H/D exchange products in the solution phase support the presence of amino and nitrile functionalities in these (highly unsaturated) "tholin" compounds. The present work demonstrates that ESI-MS coupled with FT-ICR is a suitable and "intact" method to analyze tholin components formed under anaerobic conditions; only species with C(x)H(y)N(z) are detected for freshly prepared and harvested samples. However, when intentionally exposed to water, oxygen-containing compounds are unambiguously detected.     

Atmospheric Pressure Photo Ionization Hydrogen/Deuterium Exchange Mass Spectrometry—a Method to Differentiate Isomers by Mass Spectrometry

In this report, a method for in-source hydrogen/deuterium (H/D) exchange at atmospheric pressure is reported. The method was named atmospheric pressure photo ionization hydrogen/deuterium exchange mass spectrometry (APPI HDX MS). H/D exchange was performed by mixing samples dissolved in toluene with CH₃OD solvent and analyzing the mixture using atmospheric pressure photo ionization mass spectrometry (APPI-MS). The APPI HDX spectra obtained with contact times between the analyte solution and methanol-OD (CH₃OD) of?<?0.5 s or 1 h showed the same pattern of H/D exchange. Therefore, it was concluded that APPI HDX occurred in the source but not in the solution. The proposed method does not require a specific type of mass spectrometer and can be performed at atmospheric pressure. H/D exchange can be performed in any laboratory with a mass spectrometer and a commercial APPI source. Using this method, multiple H/D exchanges of aromatic hydrogen and/or H/D exchange of active hydrogen were observed. These results demonstrated that H/D exchange can be used to distinguish between isomers containing primary, secondary, and tertiary amines, as well as pyridine and pyrrole functional groups.

Speciation of nitrogen containing aromatics by atmospheric pressure photoionization or electrospray ionization fourier transform ion cyclotron resonance mass spectrometry

We determine the elemental compositions of aromatic nitrogen model compounds as well as a petroleum sample by atmospheric pressure photoionization (APPI) and electrospray Ionization (ESI) with a 9.4 Tesla Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer. From the double-bond equivalents calculated for the nitrogen-containing ions from a petroleum sample, we can infer the aromatic core structure (pyridinic versus pyrrolic nitrogen heterocycle) based on the presence of M(+.) (odd-electron) versus [M+H](+) (even-electron) ions. Specifically, nitrogen speciation can be determined from either a single positive-ion APPI spectrum or two ESI (positive- and negative-ion) spectra. APPI operates at comparatively higher temperature than ESI and also produces radical cations that may fragment before detection. However, APPI fragmentation of aromatics can be eliminated by judicious choice of instrumental parameters.     

Synthesis of C59Hx and C58Hx fullerenes stabilized by hydrogen

Prolonged hydrogenation of C(60) molecules by reaction with H(2) at elevated temperature and pressure results in fragmentation and collapse of the fullerene cage structure. However, fragments can be preserved by immediate termination of dangling bonds by hydrogen. Here we demonstrate that not only fullerene fragments but also hydrogenated fragmented fullerenes (e.g., C(58)H(40) and C(59)H(40)) can be synthesized in bulk amount by high-temperature hydrogenation of C(60). We confirm successful synthesis of these species by matrix-assisted laser desorption ionization time-of-flight mass spectrometry and complete speciation of the resultant complex fullerene mixtures by high-resolution field desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry.     

Structural characterization of phosphatidylcholines by atmospheric pressure photoionization mass spectrometry

The potential of atmospheric pressure photoionization was investigated for the structural analysis of phosphatidylcholine lipids (PCs). [M+H]+ ions of high abundance were obtained, along with several fragment ions. Three of these dissociation products corresponded to quite unusual fragmentation pathways but allowed the determination of both the nature and the position on the glycerol backbone (sn-1 or sn-2) of the fatty acyl chains. The loss of a methyl group from the choline head was also observed. These results suggest a complex ionization mechanism in APPI. However, this method proved to be very powerful for the rapid structural analysis of PC species without using MS/MS experiments.     

Interactions of Pb2+ with fulvic acid by electrophoretically mediated on-capillary microanalysis

Studies of yessotoxin involving confirmation of fragmentation processes using a high-resolution orthogonal hybrid quadrupole time-of-flight (QqTOF) mass spectrometer and nanoLC hybrid quadrupole TOF MS have been undertaken. The fragmentation of YTX was studied in negative mode using nano electrospray (nanoESI) QqTOF mass spectrometry. Three major molecule-related ions were observed, [M - 2Na + H]-, [M - Na]- and [M - 2Na]2-, and fragmentation of the latter was studied in detail. This showed that product ions were formed as a consequence of charge-remote fragmentation processes that included a strong directional cleavage of the polyether rings of YTX. NanoLC coupled with QqTOF MS was used to determine YTX in small samples of the phytoplankton, Protoceratium reticulatum, by monitoring the [M - 2Na]2- ion at m/z 570. A PepMap C18 nanoLC column (75 microm x 10 cm, 100 A, 3 microm, LC Packings) was used and the solvent was acetonitrile/water (90:10 (v/v)) containing 1 mM ammonium acetate, at a flow rate of 400 nl/min, for 30 min. Calibrations obtained with YTX standard solutions were linear over four orders of magnitude, 0.75-250 ng/ml; r2 = 0.9947-0.9998. Phytoplankton cells (ca. 100-300) were picked, extracted with methanol/water (40:60), and the YTX concentration was determined over the range 0.011-0.020 ng/cell. The detection limit (3 x S/N) of this method was ca. 0.5 pg YTX on-column.     

Comparison of atmospheric pressure photoionization and electrospray ionization mass spectrometry for the analysis of UV filters

A comparison was made between the electrospray ionization (ESI) and atmospheric pressure photoionization (APPI) tandem mass spectrometric (MS/MS) responses of eleven ultraviolet (UV) filters. Four of the target compounds were favourably ionized in negative ion mode, and the other seven compounds in positive ion mode. For nine of the compounds APPI generated a similar response to that of ESI, but the APPI signal‐to‐noise (S/N) ratios were 1.3–60 times higher. The two most polar of the UV filter compounds (PBSA and BP‐4) were more efficiently ionized by ESI, offering higher signal intensities and lower detection limits. APPI was, however, less susceptible to ion suppression than ESI when real samples were injected. In order to optimize the APPI conditions different dopant solvents were examined to enhance the efficiency of the photoionization process. Among the evaluated dopants, toluene was selected as the best compromise. At a toluene flow rate of 10% of the solvent flow rates the ionization response increased by a factor of 40–50 over the use of no dopant for the compounds in positive ion mode and by more than 300 for the compounds in negative ion mode. Copyright © 2009 John Wiley & Sons, Ltd.     

Improved abundance sensitivity of molecular ions in positive-ion APCI MS analysis of petroleum in toluene

Positive-ion atmospheric pressure chemical ionization (APCI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) analyses of petroleum sample were performed with higher sensitivity by switching the solvent composition from toluene and methanol or acetonitrile to a one-component system consisting only of toluene. In solvent blends, molecular ions were more abundant than were protonated ions with increasing percentages of toluene. In 100% toluene, the double-bond equivalence (DBE) distributions of molecular ions obtained by APCI MS for each compound class were very similar to those obtained in dopant assisted atmospheric pressure photo ionization (APPI) MS analyses. Therefore, it was concluded that charge-transfer reaction, which is important in toluene-doped APPI processes, also plays a major role in positive-ion APCI. In the DBE distributions of S₁, S₂, and SO heteroatom classes, a larger enhancement in the relative abundance of molecular ions at fairly specific DBE values was observed as the solvent was progressively switched to toluene. This enhanced abundance of molecular ions was likely dependent on molecular structure.     

Hydrogen adsorption on Pd- and Ru-doped C60 fullerene at an ambient temperature

Palladium- and ruthenium-doped C(60) fullerene compounds were synthesized by incipient wetness impregnation of C(60) fullerene with the corresponding metal acetylacetonate precursors. Transmission electron microscopy (TEM) imaging of the metal-doped C(60) fullerene samples showed different dispersion morphologies of palladium and ruthenium particles on the C(60) matrix. Raman spectra revealed a drastic decrease in peak intensity followed by disappearance of several bands indicating the distortion of the C(60) cage structure. The amorphous nature of the C(60) fullerene compounds was confirmed by the X-ray diffraction study. Hydrogen adsorption amount of 0.85 wt % and 0. 69 wt % on Pd-C(60) and Ru-C(60), respectively, as compared to 0.3 wt % on the pure C(60) fullerene were measured at 300 bar and 298 K. The enhancement in the hydrogen uptakes can be attributed to several factors, including adsorption of molecular H(2) on the defect sites, metallic hydride formation, spillover of hydrogen, and bond formation with atomic hydrogen with different active sites of carbon of host fullerene. The hydrogen adsorption isotherms are of type III and can be correlated by the Freundlich (for Ru-C(60)) and modified Oswin equations (for Pd-C(60) and pristine C(60)).     

Elucidation of the fragmentation pathways of different phosphatidylinositol phosphate species (PIPx) using IRMPD implemented on a FT-ICR MS

This work reports on the fragmentation of phosphoinositides by tandem mass spectrometry (MS/MS) and MS3 experiments on a hybrid apex-Qe Fourier transform-ion cyclotron resonance mass spectrometer (FT-ICR MS) using internal infrared multiphoton dissociation (IRMPD). The fragmentation behavior of diacylphophatidylinositol triphosphate was intensively studied since an abundant loss of inositol biphosphate was observed. This loss was suggested to occur via phosphate migration along the inositol head group. Substantiation by MS3 experiments showed that this neutral loss is formed after the loss of water from the precursor ion, indicating phosphate migration along the inositol ring to the glycerol backbone. Further fragmentation of the ion formed by the loss of inositol biphosphate from diacylphophatidylinositol triphosphate resulted in the formation of a product ion with a molecular formula of C(3)H(5)O(7)P(2), corresponding to a glycerol backbone linked to two phosphate groups. We suggested different structures for this ion and compared their stability using modeling experiments.     

Dimerization of ionized 4‐(methyl mercapto)‐phenol during ESI,APCI and APPI mass spectrometry

A novel ion/molecule reaction was observed to occur under electrospray ionization (ESI), atmospheric pressure chemical ionization (APCI), and atmospheric pressure photo ionization (APPI) conditions, leading to dimerization of ionized 4‐(methyl mercapto)‐phenol followed by fast H^· loss. The reaction is particularly favored during ESI, which suggests that this ion/molecule reaction can occur both in the solution inside the ESI‐charged droplets and in the gas‐phase environment of most other atmospheric pressure ionization techniques. The dimerization reaction is inherent to the electrolytic process during ESI, whereas it is more by ion/molecule chemistry in nature during APCI and APPI. From the tandem mass spectrometry (MS/MS) data, accurate mass measurements, hydrogen/deuterium (H/D) exchange experiments and density functional theory (DFT) calculations, two methyl sulfonium ions appear to be the most likely products of this electrophilic aromatic substitution reaction. The possible occurrence of this unexpected reaction complicates mass spectral data interpretation and can be misleading in terms of structural assignment as reported herein for 4‐(methyl mercapto)‐phenol. Copyright © 2009 John Wiley & Sons, Ltd.     

Towards analytically useful two-dimensional Fourier transform ion cyclotron resonance mass spectrometry

Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry (MS) achieves high resolution and mass accuracy, allowing the identification of the raw chemical formulae of ions in complex samples. Using ion isolation and fragmentation (MS/MS), we can obtain more structural information, but MS/MS is time- and sample-consuming because each ion must be isolated before fragmentation. In 1987, Pfändler et al. proposed an experiment for 2D FT-ICR MS in order to fragment ions without isolating them and to visualize the fragmentations of complex samples in a single 2D mass spectrum, like 2D NMR spectroscopy. Because of limitations of electronics and computers, few studies have been conducted with this technique. The improvement of modern computers and the use of digital electronics for FT-ICR hardware now make it possible to acquire 2D mass spectra over a broad mass range. The original experiments used in-cell collision-induced dissociation, which caused a loss of resolution. Gas-free fragmentation modes such as infrared multiphoton dissociation and electron capture dissociation allow one to measure high-resolution 2D mass spectra. Consequently, there is renewed interest to develop 2D FT-ICR MS into an efficient analytical method. Improvements introduced in 2D NMR spectroscopy can also be transposed to 2D FT-ICR MS. We describe the history of 2D FT-ICR MS, introduce recent improvements, and present analytical applications to map the fragmentation of peptides. Finally, we provide a glossary which defines a few keywords for the 2D FT-ICR MS field.     

A preconcentrator coupled to a GC/FTMS: Advantages of self-chemical ionization,mass measurement accuracy,and high mass resolving power for GC applications

Coupling of a cryogenic preconcentrator (PC) to a gas chromatograph/Fourier transform ion cyclotron resonance mass spectrometer (GC/FT-ICR MS) is reported. To demonstrate the analytical capabilities of the PC/GC/FT-ICR MS, headspace samples containing volatile organic compounds (VOCs) emitted from detached pine tree twigs were analyzed. Sub-ppm mass measurement accuracy (MMA) for highly resolved (m/Deltam(50%) > 150 k) terpene ions was achieved. Direct PC/GC/FT-ICR MS analyses revealed that detached twigs from pine trees emit acetone, camphor, and four detectable hydrocarbon isomers with C(10)H(16) empirical formula. The unknown analytes were identified based on accurate mass measurement and their mass spectral appearances. Authentic samples were used to confirm initially unknown identifications. Self-chemical-ionization (SCI) reactions furnished an additional dimension for rapid isomer differentiation of GC eluents in real time.     

Hydrogen capacity of palladium-loaded carbon materials

Several samples of palladium-loaded single-wall carbon nanotubes and palladium-loaded MAXSORB activated carbon were prepared by means of the reaction of the raw carbon support with Pd2(dba)3.CHCl3. When carbon nanotubes were used as the support, the palladium content in the samples reached 13-31 wt % and fine particles of 5-7 nm average size were obtained. In the case of the samples with MAXSORB as the support, the palladium content was higher (30-50 wt %) and the particle size larger (32-42 nm) than in the nanotube samples. At 1 atm and room temperature, the hydrogen capacity of the palladium-loaded samples exceeds 0.1 wt % and is much higher than the capacity of the raw carbon supports (less than 0.01 wt %). The maximum hydrogen capacity at 1 atm and room temperature was found to be 0.5 wt %. A maximum hydrogen capacity of 0.7 wt % was obtained at 90 bar in a palladium-loaded MAXSORB sample, while the capacities for the raw carbon nanotubes and MAXSORB at the same pressure were 0.21 and 0.42 wt %, respectively. At low pressure, it was observed that the H/Pd atomic ratios in the palladium-loaded samples were always higher than in the bulk Pd. The spillover effect is considered as a possible cause of the high H/Pd atomic ratios. On the other hand, the effect of the pressure increase on the spillover was observed to be very low at high pressure and room temperature.     

Comparison of electrospray ionization,atmospheric pressure chemical ionization,and atmospheric pressure photoionization for the analysis of dinitropyrene and aminonitropyrene LC-MS/MS

The only relevant source for human exposure to dinitropyrenes is diesel engine emissions. Due to this specificity, dinitropyrenes may be used as biomarkers for monitoring human exposure to diesel engine emissions. Only few analytical methods have been described for the quantitation of dinitropyrenes and their metabolites, aminonitropyrenes, and diaminopyrenes. Therefore, for dinitropyrenes, aminonitropyrenes, and diaminopyrenes were selected as model compounds for the development of a sensitive HPLC-MS/MS method (high performance liquid chromatography coupled to triple quadrupole mass spectrometry) was to quantify polyaromatic amines and nitroarenes in biological matrices was developed optimal methods by comparing electrospray ionization (ESI), atmospheric pressure chemical ionization (APCI), and atmospheric pressure photoionization (APPI) sources. Dinitropyrene was not effectively ionized and diaminopyrene yielded mainly [M(.)](+) ions by electrospray ionization. With APCI and APPI, precursor ions of diaminopyrene and aminonitropyrene were [M + H](+) and [M(.)](-) for dinitropyrene. Precursor ions with [M - 30(.)](-) for dinitropyrene and [M - 30 + H](+) for aminonitropyrene were observed. Reversed and normal phase HPLC-MS/MS with ESI, APCI and APPI were optimized separately with respect to unequivocal analyte identification and sensitivity. Normal phase HPLC coupled to APPI-MS/MS gave the highest precision and sensitivity for aminonitropyrene (6%/0.2 pg on column) and dinitropyrene (9%/0.5 pg on column). The limit of detection in spiked rat plasma was 5 pg/100 microL for aminonitropyrene (accuracy 82%) and 10 pg/100 microL for dinitropyrene (accuracy 105%). In plasma of rats treated with dinitropyrene by oral administration, no detectable levels of dinitropyrene but higher aminonitropyrene levels compared with intratracheal instillation were observed. These findings clearly demonstrate that dinitropyrene was absorbed after oral and intratracheal application and that a reduction of nitro groups occurs to a high extent in the reductive environment of the intestine. To our knowledge, this is the first time that aminonitropyrene was observed in plasma after intratracheal or oral administration directly demonstrating the reductive metabolism of dinitropyrene in vivo.     

Solid-phase microextraction liquid chromatography/tandem mass spectrometry for the analysis of chlorophenols in environmental samples

Liquid chromatography with atmospheric pressure chemical ionisation mass spectrometry (LC/APCI-MS), using negative ion detection in a triple quadrupole instrument, was used for the determination of chlorophenols (CPs) in environmental samples. In-source collision-induced dissociation (CID) was compared with MS/MS fragmentation. In general, less fragmentation was observed in MS/MS as compared with in-source CID, with the latter providing more intense fragment ions due to chemical ionisation. Under MS/MS conditions [M - H - HCl](-) was the main fragment ion observed for all compounds except for pentachlorophenol, which showed no fragmentation. For multiple reaction monitoring (MRM) acquisition mode, the transition from [M - H](-) to [M - H - HCl](-) was selected, leading to detection limits down to 0.3 ng injected. Direct and headspace-solid-phase microextraction (HS-SPME) were used as preconcentration procedures for the analysis of CPs in wood and in industrially contaminated soils. CPs were quantified by standard addition, which led to good reproducibility (RSD between 4 and 11%) in both SIM and MRM modes, and detection limits down to ng/g. The combination of MS/MS and in-source CID allowed confirmation of the presence of CPs in environmental samples.     

A Comparative Study of Pyrolysis Liquids by Slow Pyrolysis of Industrial Hemp Leaves,Hurds and Roots

This study assessed the pyrolysis liquids obtained by slow pyrolysis of industrial hemp leaves, hurds, and roots. The liquids recovered between a pyrolysis temperature of 275–350 °C, at two condensation temperatures 130 °C and 70 °C, were analyzed. Aqueous and bio-oil pyrolysis liquids were produced and analyzed by proton nuclear magnetic resonance (NMR), gas chromatography–mass spectrometry (GC-MS), and atmospheric pressure photoionization Fourier transform ion cyclotron resonance mass spectrometry (APPI FT-ICR MS). NMR revealed quantitative concentrations of the most abundant compounds in the aqueous fractions and compound groups in the oily fractions. In the aqueous fractions, the concentration range of acetic acid was 50–241 gL⁻¹, methanol 2–30 gL⁻¹, propanoic acid 5–20 gL⁻¹, and 1-hydroxybutan-2-one 2 gL⁻¹. GC-MS was used to compare the compositions of the volatile compounds and APPI FT-ICR MS was utilized to determine the most abundant higher molecular weight compounds. The different obtained pyrolysis liquids (aqueous and oily) had various volatile and nonvolatile compounds such as acetic acid, 2,6-dimethoxyphenol, 2-methoxyphenol, and cannabidiol. This study provides a detailed understanding of the chemical composition of pyrolysis liquids from different parts of the industrial hemp plant and assesses their possible economic potential.     

Analysis of dihydropyridine calcium channel blockers using negative ion photoionization mass spectrometry

The fragmentation of dihydropyridine calcium-channel antagonists are compared by electrospray ionization (ESI) and atmospheric pressure photonization (APPI). The results demonstrate that in ESI the preferred ionization process is in positive mode, with the mass spectra of [M+H]+ showing base peak ions probably formed by loss of alcohols from carboxyl groups. Conversely, in APPI, a high intense peak is observed in negative mode due to deprotonated molecule [M-H]- after two serial 1, 2-hydride shifts leading to a rearranged deprotonated molecule [M-H]-. These ions undergo another 1,2-hydride shifts to produce a nitro-phenyl product ion of m/z 122. The APPI is also used to develop a method for the quantitation of dihydropyridines (e.g., nifedipine) in human plasma.