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International audience; Petroporphyrins, geoporphyrins, or metalloporphyrins are the original petroleum biomarkers, identified by Alfred Treibs more than a century ago and the first molecular evidence for the biogenic origins of petroleum. Since discovery, analytical strategies have been developed to identify porphyrins in petroleum and its fractions. This review focuses on the advances enabled by ultrahigh resolving power Fourier transform ion cyclotron resonance mass spectrometry in tribute to Professor Alan G. Marshall.

Naphthenic acid (NA) fractions from heavy crude oils are typically analyzed in mass spectrometry via electrospray ionization (ESI). Here, we show that NA analysis is also possible by MALDI using a highly basic matrix (proton sponge). When compared with ESI, that allowed detection of six compound families, MALDI resulted in the observation of twenty-two compound families. Besides, MALDI analysis affords compositional-dependent information. Unlike ESI, where all NAs are detected as deprotonated molecules, in MALDI we observe both deprotonated molecules and radical anions. This indicates that ion formation in NA by MALDI can occur by either acid-base and electron-capture mechanisms, or both. Interestingly, the preferred ionization channel seems to be compound class dependent; for instance, the acid base mechanism (which allows detection of deprotonated NA species through a Bronsted-Lowry reaction) applies exclusively to NAs with high H/C ratios along the whole O/C range. On the other hand, for less saturated compounds both mechanisms apply, while the electron capture channel occurs exclusively in species with low H/C and high O/C ratios or high H/C and low O/C ratios (envelope of the van Krevelen plots). In summary, we demonstrate that MALDI(-) is an alternative method for the analysis of complex petrochemical samples offering additional advantages, when compared with ESI, such as increasing compositional space accessibility for polar samples, high throughput and exceptional tolerance to the presence of impurities and salts in the samples. Furthermore, exploration on semi-quantitative approaches in MALDI can provide additional advantages such as those offered by LC-ESI MS, currently used to quantify naphthenic acids.

We report on a matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF) method to analyze naphthenic acids (NAs), from petrochemical samples, using 9-aminoacridine (9-AA) and a proton sponge 1,8-bis(dimethylamino) naphthalene (DMAN), as matrices. Singly charged deprotonated molecules of NAs, [M−H] − , dominated the negative ion MALDI mass spectra. The negative ions were pre-formed in solution through an acid/base Bronsted-Lowry reaction promoted by the highly basic matrices (9-AA and DMAN). The DMAN afforded cleaner spectra with absence of clusters, aggregates or matrix interferences at low m / z ; in addition, it provides molecular weight distributions similar to those observed with negative ion electrospray ionization (ESI). In contrast, MALDI spectra obtained with 9-AA exhibits matrix interferences at low mass, and bias towards aliphatic NAs. Finally, we observe the presence of monomeric species in the low mass region and non-covalent aggregates at higher masses in the negative mode MALDI spectra with both matrices, much like with negative mode ESI. We demonstrate that MALDI-TOF/MS is a viable tool for NAs analyses with added advantages such as high throughput and exceptional tolerance to the presence of impurities and salts in the samples, when compared with ESI.

Electron-transfer ionization in matrix-assisted laser desorption/ionization (ET-MALDI) is widely used for the analysis of functional materials that are labile, unstable, and reactive in nature. However, conventional ET matrices (e.g., trans-2-[3-(4- tert-butylphenyl)-2-methyl-2-propenylidene] malononitrile (DCTB)) still lack in performance due to cluster formation, reactivity with analytes, and vacuum instability. In this contribution, we report the use of α-cyanophenylenevinylene derivatives as UV MALDI matrices for the analysis, by ET ionization, of nanoparticles, polymers, porphyrins, and fullerenes. The synthetic versatility of the phenylenevinylene (PV) core allowed us to modulate physicochemical properties, fundamental for efficient formation of primary ions in the gas phase under MALDI conditions, such as planarity, ionization potentials, molar absorptivity, and laser thresholds. For instance, introduction of -CN groups in vinyl positions of the PV core induced structural disruption in planarity in the new α-CNPV derivatives, shifting their maximum molar absorptivity to UV wavelengths and increasing their ionization energy values above 8.0 eV. UV MALDI-relevant photophysical properties in solution and solid state are reported (λ

Separation strategies coupled with HRMS analysis are vital to increase the scope of the instrumental technique. In this work, we use extrography and column chromatography as fractionation tools for increasing compositional space accessibility in the APPI-FT-ICR mass spectrometric analysis of heavy crude oils. Extrography fractionation was performed on a crude oil sample adsorbed on neutral alumina, using an elutropic series. The crude oil was adsorbed on neutral alumina, and then we applied Soxhlet extraction using acetonitrile, methanol, n-heptane, and toluene, to obtain fractions enriched in metal complexes, polar compounds, maltenes, and asphaltenes, respectively. Considering that polar compounds are responsible for complex operational problems such emulsion and deposit formation, we fractioned the polar extract using normal phase column chromatography to obtain six additional subfractions. All of the extracts were analyzed by APPI FT-ICR mass spectrometry. We detected eleven compound classes in fractions and sub-fractions which were undetectable when analyzing the entire crude oil sample. In terms of the number of molecular formulas, the whole crude oil sample exhibits ∼3700 while ∼11,800 compounds were detected in extrography fractions and column chromatographic sub-fractions. These results indicate that combination of extrography and column chromatography increase compositional space accessibility in around 70%. Specifically, fractionation processes allowed the detection of several compound classes such as NnSs, NnOo, OoSs, NnOoSs (with n = 1; s = 1, 2, 3; o = 1, 2, 3), and N4O1V1, which were undetectable in the analysis of the whole crude oil.

In this contribution, we use high-resolution mass spectrometry to unveil the molecular composition of occluded compounds inside Colombian asphaltenes macrostructures. We use Soxhlet extraction, with n-heptane, coupled with asphaltene maceration to obtain four fractions enriched with chemical compounds occluded inside asphaltene networks. We focused our efforts on the fraction enriched with compounds interacting with asphaltenes via strong intermolecular forces, and used normal phase column chromatography to fractionate it and atmospheric pressure photoionization coupled to Fourier transform ion cyclotron resonance mass spectrometry to obtain a detailed molecular description. Our results indicate that the occluded compounds obtained in the last stage of the washing process are by themselves a complex mixture, consisting mostly of saturated compounds including molecular formulas corresponding to biomarkers, alkyl aromatics with high heteroatom content (up to four heteroatoms), vanadyl porphyrins, and highly...

With heavy crude oil refining on the rise, upgrading strategies are fundamental to yield high-value products. Hydroconversion and thermal cracking are well-established and widely used upgrading processes for heavy oils’ distillation cuts and residues. Recognizing molecular changes in these fractions after upgrading, particularly of asphaltenic compounds, is fundamental to understand and optimize the processes. In this work, we follow compositional changes in the asphaltene fraction of a Colombian heavy crude, after hydroconversion and thermal cracking, using high-resolution mass spectrometry. The liquid products from the upgrading processes were fractionated into maltenes and residual asphaltenes, with yields between 33% and 38% in maltenes from the original asphaltene feedstock. Contoured plots of double bond equivalents versus carbon number and van Krevelen diagrams show maltenic fractions exhibiting lower aromaticity, smaller molecular size, fewer heteroatomic species, and higher content of alkyl side ...

Asphaltene adsorption properties on mineral surfaces are fundamental to understanding wettability changes in rocks and fluid behavior in reservoirs. In this contribution we report an analytical approach to investigate the molecular features responsible for asphaltene–silica interactions. We used high performance thin layer chromatography silica plates and an elutropic series of solvents to fractionate asphaltenes according to their particular affinity with the mobile and stationary phases. We observed three characteristic asphaltene fractions (with Rfs of 0, 0.69, and 0.90), which were in turn desorbed and analyzed by atmospheric pressure photoionization FT-ICR mass spectrometry (APPI-FT-ICR-MS). In general, polar noneluted compounds highly retained by the silica surface with Rf = 0 exhibit molecular compositions with N1, NnOo and Oo (o = 1, 2, 3 and n = 1, 2) classes and the lowest H/C ratios compared to the other subfractions. Polar CH2Cl2:MeOH-eluted compounds, with Rf = 0.69, have predominantly HC, N...

The synthesis and characterization of the nickel(II) complexes of a series of pentadentate and hexadentate aminopyridine ligands that contain ethylenediamine and/or propylenediamine groups are described. The ligands include: 1,12-bis(2-pyridyl)-2,5,8,11-tetraazadodecane, TRIEN-pyr; 1,13-bis(2-pyridyl)-2,5,9,12-tetraazatridecane, DIEN-PN-pyr; 1,14-bis(2-pyridyl)-2,6,9,13-tetraazatetradecane, DIPN-EN-pyr; 1,15-bis(2-pyridyl)-2,6,10,14-tetraazapentadecane, TRIPN-pyr; 1,9-bis(2-pyridyl)-2,5,8-triazanonane, DIEN-pyr; and 1,11-bis(2-pyridyl)-2,6,10-triazaundecane, DIPN-pyr. The following methods were used to determine the binding geometries of the nickel(II) complexes in the solid, solution, and gas phases: magnetic susceptibility measurements, absorption spectroscopy, EPR spectroscopy, electrochemistry, and electrospray ionization mass spectrometry. All of the ligands form 6-coordinate compounds in the solid, liquid, and gas states, with the exception of the TRIEN-pyr, DIEN-PN-pyr(partially), DIPN-pyr, and DIEN-pyr ligands which form 5-coordinate species in the gas state. All of the complexes could be oxidized to Ni(III) species electrochemically, although the Ni(III) complexes of TRIPN-pyr and DIPN-pyr were much less stable than the other four ligands. EPR spectra of the frozen solutions showed the low spin d7 Ni(III) complexes of TRIEN-pyr and DIPN-EN-pyr to be similar to those that have been found for poly-aza macrocyclic compounds.

Gas-phase ion–molecule reactions of metal complex ions with acetonitrile in a quadrupole ion trap mass spectrometer are shown to have some potential for determining the number and types of functional groups bound to a metal. Metal complexes with varying coordination spheres show significant differences in their gas-phase reactivity with acetonitrile. The relative product ion intensities observed in the mass spectrum after a given reaction time provide the appropriate data to distinguish complexes with different coordination spheres. Experimental parameters suspected to have an effect on the reproducibility of these intensities are examined in order to understand better which factors need to be most closely controlled to maximize precision. Ni(II) and Cu(II) complex ions of the pentadentate ligands 1,9-bis(2-imidazolyl)-2,5,8-triazanonane (DIEN-(imi)2) and 1,9-bis(2-tetrahydrofuranyl)-2,5,8-triazanonane (DIEN-(THF)2) are reacted in the gas-phase at different temperatures, pressures of acetonitrile, and pressures of buffer gas (helium) in a modified quadrupole ion trap mass spectrometer. The effects of such experimental variations on the product ion intensities are measured and analyzed. Under conditions where the precision is maximized, the temperature and acetonitrile pressure seem to have the biggest impact on the reproducibility of the resulting product ion intensity with the acetonitrile level being slightly more important. The reproducibility of ion intensities for the reactions of the Ni(II) complexes are the lowest due to their higher reactivity, while the measurements for the Cu(II) complexes have a higher degree of precision. In general, with careful control of the temperature and reagent gas pressure, ion–molecule (I–M) reactions seem to be a promising method for providing a rapid and sensitive analysis of the functional groups bound to a metal in a given complex.

Essential oils from fruit peel and leaves of colombian lemon ( Citrus volkameriana ), mandarin ( C. reticulata ) and orange ( C. sinensis ) were obtained by steam distillation and/or cold pressing. The extracts were analysed by high-resolution gas chromatography using either a flame ionization detector or a mass selective detector (electron impact ionization, 70 eV). The oil constituents were identified according to their mass spectra and Kova´ts retention indices determined on both polar and non-polar stationary phase capillary columns. The concentration of volatile secondary metabolites was maximum when the citrus fruits were at an intermediate maturation stage characterized by a greenish yellow coloration (45–75% green). While citrus peel oils contained from 94.01 to 98.66% of monoterpenes (C 10 H 16 ), limonene as a major component and from 0.82 to 5.84% of oxygenated compounds, the extracts from citrus leaves contained only 65.26, 31.23 and 79.43% of monoterpenes (C 10 H 16 ) in lemon, mandarin and orange, respectively. Oxygenated compounds in these oils represented 33.08, 68.47 and 16.38%, respectively.

Five-coordinate metal complex ions of the type [ML](2+) [where M = Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II) and L= 1,9-bis(2-pyridyl)-2,5,8-triazanonane (DIEN-(pyr)(2)) and 1,9-bis(2-imidazolyl)-2,5,8-triazanonane (DIEN-(imi)(2)] have been reacted with acetonitrile in the gas phase using a modified quadrupole ion trap mass spectrometer. The kinetics and thermodynamics of these reactions show that the reactivity of these complexes is affected by metal electronic structure and falls into three groups: Mn(II) and Ni(II) complexes are the most reactive, Fe(II) and Co(II) complexes exhibit intermediate reactivity, and Cu(II) and Zn(II) complexes are the least reactive. To help explain the experimental trends in reactivity, theoretical calculations have been used. Due to the relatively large size of the metal complexes involved, we have utilized a two-layered ONIOM method to perform geometry optimizations and single point energy calculations for the [ML](2+) and [ML + CH(3)CN](2+) systems. The calculations show that the reactant five-coordinate complexes ([ML](2+)) exhibit structures that are slightly distorted trigonal bipyramidal geometries, while the six-coordinate complexes ([ML + CH(3)CN](2+)) have geometries that are close to octahedral. The Delta G values obtained from the ONIOM calculations roughly agree with the experimental data, but the calculations fail to completely explain the trends for the different metal complexes. The failure to consider all possible isomers as well as adequately represent pi-d interactions for the metal complexes is the likely cause of this discrepancy. Using the angular overlap model (AOM) to obtain molecular orbital stabilization energies (MOSE) also fails to reproduce the experimental trends when only sigma interactions are considered but succeeds in explaining the trends when pi interactions are taken into account. These results indicate that the pi-donor character of the CH(3)CN plays a subtle, yet important, role in controlling the reactivity of these five-coordinate complexes. Also, the AOM calculations are consistent with the experimental data when the [ML](2+) complexes have high-spin trigonal bipyramidal configurations. Generally, these results suggest that ion-molecule reactions can be very sensitive to metal complex coordination geometry and thus may have some promise for providing gas-phase coordination structure.

Triphenylamine ortho-tricarboxylic acid (1) has been synthesized and the crystal structure reported. This molecule is shown to spontaneously self-assemble into a hydrogen-bonded tetrahedron. Furthermore, Electrospray Ionization Mass Spectroscopy shows evidence for the stability of such aggregates from an ethanol/water solution.