Andras Gaspar

Impact of Different Ionization Methods on the Molecular Assignments of Asphaltenes by FT-ICR Mass Spectrometry

Over the years, ultrahigh resolution mass spectrometry has successfully illustrated the extreme complexity of crude oil and related solubility or polarity based fractions on a molecular level. However, the applied ionization technique greatly influences the outcome and may provide misleading information. In this work, we investigate the atmospheric pressure laser ionization (APLI) technique coupled with Fourier transform ion cyclotron resonance mass spectrometer to analyze the asphaltene fraction of a crude oil. These results were compared to data obtained by using other existing atmospheric pressure ionization methods. Furthermore elemental analysis and solid state NMR were used to obtain the bulk characteristics of the asphaltene sample. The results of the different ionization techniques were compared with the bulk properties in order to describe the potential discrimination effects of the ionization techniques that were observed. The results showed that APLI expands the range of the assigned molecules, while retaining information already observed with the generally used ion sources.

Molecular and structural characterization of dissolved organic matter during and post cyanobacterial bloom in Taihu by combination of NMR spectroscopy and FTICR mass spectrometry

Seasonal molecular changes in dissolved organic matter (DOM) isolated from Tai Lake (Taihu) both during (June) and following (November) an algal bloom event in 2007 were characterized by nuclear magnetic resonance spectroscopy (NMR) and Fourier transform ion cyclotron resonance (FTICR) mass spectrometry. Considerable biosignatures were present in summer DOM, yet with a near absence of algal extract compounds. Extensive molecular alteration resulting from multistep and massively parallel biotic and subordinated abiotic transformations of algal biomass to DOM included loss and synthesis of carbohydrates, fundamental changes of aromatic compounds and progressive formation of carboxyl-rich alicyclic compounds (CRAM). The DOM transformation from summer to fall resulted in smaller molecules, increased abundance of CHNO continuous molecular series and overall molecular diversity. Analysis of MS-derived compositional networks placed summer DOM in-between the algal extract and fall DOM. Metabolic pathway annotation by means of high-resolution mass analysis provided a wide range of pathways associated with secondary metabolites in DOM and more basic ones like carbohydrate metabolism characteristic of algal extract compounds. Overall, the time-dependent molecular signature of Taihu DOM was likely dominated by microbial metabolism rather than abiotic chemical transformations. Results from this study indicate that high-resolution organic structural spectroscopy resolves meaningful structural detail out of complex environmental mixtures and has the potential to contribute significantly to future functional biodiversity studies.

Expanding the data depth for the analysis of complex crude oil samples by Fourier transform ion cyclotron resonance mass spectrometry using the spectral stitching method

RATIONALE Crude oil samples are very complex mixtures of compounds and only Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) provides the ultra-high mass resolution necessary to resolve them. However, FT-ICR MS operates best when only a small amount of ions is present during each transient. This cannot be accomplished with crude oil samples without chromatography because more than 50,000 compounds can be present, with the result that species with low intensity may be suppressed and are detected either with low intensity or not at all. METHODS Spectral stitching was used to overcome the problems associated with suppression effects, where only short mass windows of 30 amu were scanned to reduce the amount of ions present in each individual scan. Afterwards, all the scans were co-added and the subsequent spectrum was used to calculate individual class distributions. RESULTS A heavy crude oil sample was analyzed using spectral stitching and this approach was compared with analysis using a broadband-method in order to illustrate the enhancement in depth of information. Although both methods took the same analysis time a seven-times increase in the number of detected species was observed when the spectral stitching method was used compared with the commonly applied broadband method in a 900 amu mass window. CONCLUSIONS Spectral stitching using smaller selected ion monitoring (SIM) windows for complex crude oil samples allows better class distribution to be obtained because less ion suppression is observed.

Combined utilization of ion mobility and ultra‐high‐resolution mass spectrometry to identify multiply charged constituents in natural organic matter

Natural organic matter as complex biogeochemical non-repetitive material was investigated with ion mobility mass spectrometry (IMS) and ultra-high-resolution Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) approaches in order to unravel the existence of multiply charged state constituents. Hereby we describe and assign the potential molecular formulae of these doubly charged species, derived from FTICR-MS, and the existence of these species was confirmed via IMS. The parallel application of these powerful techniques enabled the boundaries of the understanding of natural organic matter to be pushed further.

Studying ultra-complex crude oil mixtures by using high-field asymmetric waveform ion mobility spectrometry (FAIMS) coupled to an electrospray ionisation-LTQ-Orbitrap mass spectrometer

High-field asymmetric waveform ion mobility spectrometry (FAIMS) was coupled directly to an LTQ Orbitrap mass spectrometer to analyze a nitrogen-rich crude oil. Analyzing crude oil is extremely difficult because of the complexity, as up to 100,000 different components can be present. Therefore, simplification of crude oil increases the information content because discrimination and suppression effects are reduced. Here, the first results are presented that show that FAIMS can be an important tool for the simplification of complex mixtures. Additionally, the results show that FAIMS is an excellent tool that allows not only a simplification of such complex mixtures, but also shows the separation of isomeric compounds that have the same elemental composition but different structure and conformation.

Analysis of low molecular weight acids by monolithic immobilized pH gradient-based capillary isoelectric focusing coupled with mass spectrometry.

A novel method for the separation and detection of low molecular weight (LMW) acids was developed using monolithic immobilized pH gradient-based capillary isoelectric focusing coupled with mass spectrometry. Two main parameters, focusing conditions and delivery buffer conditions, which might affect separation efficiency, were optimized with the focusing time of 7 min at 350 V/cm and the delivery buffer of 50% (v/v) acetonitrile in 10 mmol/L ammonium formate (pH 3.0). Under these conditions, the linear correlation between the volume of delivery solvent and the pK(a) of the model components was observed. In addition, the separation mechanism of LMW acids was proposed as well. We suppose that this method may provide a useful tool for the characterization of LMW components (e.g. natural organic matter of different origins).

Letter: Identification of polyborate ions in aqueous solution by electrospray ionisation Fourier transform ion cyclotron resonance mass spectrometry

Ultra-high-resolution mass spectrometry was used to investigate polyborate species in aqueous solution. The mass spectrum of boric acid revealed clusters of polyborate ions. Constituents with up to 19 B atoms were assigned and 15 species and their relationship were investigated in depth with collision-induced fragmentation. Based on the observed fragments, we proposed herein a potential fragmentation pathway for the observed polyborate molecules.