New Separation Approach for Asphaltene Investigation: Argentation Chromatography Coupled with Ultrahigh-Resolution Mass Spectrometry

Argentation chromatography has been developed for the analysis and separation of asphaltenes. The separation is based on the interaction between the silver ions (Ag+) bonded to a silica gel surface and the π-systems of the polycondensed aromatic compounds, where the interactions can be different when heteroatoms (N, O, S) are present in the molecules. Online coupling of argentation chromatography and high-resolution mass spectrometry allows fast and detailed analysis of the separation of crude oil asphaltenes. Highly condensed aromatic compounds possessing a high degree of unsaturation can be successfully separated using a mixture of toluene and chloroform (7:3 v/v) as mobile phase and dimethyl sulfoxide as competitive ligand for elution of asphaltene compounds with double bond equivalents (DBE) of up to 40. Making use of the different structural features of the components, it is possible to separate isomeric compounds that interact with different strengths with the stationary phase. The composition of mobile phase plays a significant role in separation efficiency

Optimized asphaltene separation by online coupling of size exclusion chromatography and ultrahigh resolution mass spectrometry

The asphaltene fraction is the heaviest part of a crude oil and is obtained as the fraction which contains compounds that are not soluble in paraffinic solvents such as n-heptane. Due to the limited solubility the use of separation methods is strongly reduced to methods that include solvents that dissolve asphaltenes. Here, the direct coupling of size exclusion chromatography with ultrahigh resolution mass spectrometry to investigate the separation of asphaltenes is accomplished. Different mobile phase systems have been investigated using THF and different mixtures of chloroform and toluene to optimize the separation conditions. Due to the separation the complexity of the asphaltene sample can be reduced, therefore mass spectra with increased information depth can be obtained due to the smaller amount of interacting species. Additionally, correlations can be proposed between molecular mass and structural characteristics of highly condensed aromatic molecules: compounds having both aromatic core and long aliphatic chains with higher masses were detected earlier and the smaller ones containing mostly highly aromatic structures and only a low amount of short alkyl chains (with the same DBE values) have stronger retention. Different experimental conditions such as stationary phase and mobile phase of asphaltene separation with size exclusion chromatography are investigated

Argentation chromatography coupled to ultrahigh‐resolution mass spectrometry for the separation of a heavy crude oil

Simplification of highly complex mixtures such as crude oil by using chromatographic methods makes it possible to get more detailed information about the composition of the analyte. Separation by argentation chromatography can be achieved based on the interaction of different strength between the silver ions (Ag+) immobilized through a spacer on the silica gel surface and the π-bonds of the analytes. Heavy crude oils contain compounds with a high number of heteroatoms (N, O, S) and a high degree of unsaturation thus making them the perfect analyte for argentation chromatography. The direct coupling of argentation chromatography and ultrahigh-resolution mass spectrometry allows to continuously tracking the separation of the many different compounds by retention time and allows sensitive detection on a molecular level. Direct injection of a heavy crude oil into a ultrahigh-resolution mass spectrometer showed components with DBE of up to 25, whereas analytes with DBE of up to 35 could be detected only after separation with argentation chromatography. The reduced complexity achieved by the separation helps increasing the information depth

Electrospray ionization for determination of non-polar polyaromatic hydrocarbons and polyaromatic heterocycles in heavy crude oil asphaltenes

Electrospray ionization (ESI) is the most common ionization method in atmospheric pressure ionization mass spectrometry because of its easy use and handling and because a diverse range of components can be effectively ionized from high to medium polarity. Usually, ESI is not employed for the analysis of non-polar hydrocarbons, but under some circumstances, they are effectively ionized. Polyaromatic hydrocarbons and aromatic heterocycles can form radical ions and protonated molecules after ESI, which were detected by Fourier transform ion cyclotron resonance mass spectrometry. The highly condensed aromatic structures are obtained from a heavy crude oil, and the results show class distribution from pure hydrocarbons up to more non-basic nitrogen-containing species. By using different solvent compositions [toluene/methanol (50/50 v/v), dichloromethane/methanol (50/50 v/v), dichloromethane/acetonitrile (50/50 v/v) and chloroform], the results show that the lack of proton donor agent helps to preserve the radical formation that was created at the metal/solution interface inside the electrospray capillary. The results demonstrate that with an appropriate selection of solvent and capillary voltage, the ratio between the detected radical ion and protonated molecule form can be manipulated. Therefore, ESI can be expanded for the investigation of asphaltene and other polyaromatic systems beyond the polar constituents as non-polar hydrocarbons can be efficiently analyzed

Characterization of crude oil asphaltenes by coupling size-exclusion chromatography directly to an ultrahigh-resolution mass spectrometer

Rationale: Fossil fuels are one of the most important energy resources until new sustainable materials become available. To optimize the upgrading processes of these materials characterization of the remaining heavy materials is of great importance. Methods: Asphaltenes are the most difficult fraction of crude oil to process due to the limited number of solvents in which they can be dissolved. Chromatographic separation methods need to consider the difficulties associated with these limitations. Size-exclusion chromatography (SEC) in combination with Fourier transform Orbitrap mass spectrometry (MS) combines the capabilities of ultrahigh resolution and very high mass accuracy with a separation method that allows using solvents as mobile phase for asphaltene separation. Results: A chromatographic method was developed that shows the separation of asphaltenes according to their molecular mass. A simplification of the samples was achieved by reducing the number of compounds present in a single spectrum compared to infusion data. Direct detection by mass spectrometry additionally allows a distinction of different isomers present in the complex samples. Conclusions: Direct coupling of SEC with ultrahigh-resolution mass spectrometry allows the study of the most difficult to analyze fraction of crude oil, the asphaltene fraction. Separation reduces the complexity of individual spectra and, therefore, also reduces suppression and discrimination effects. The separation of structural isomers which cannot be characterized by MS alone gives an added dimension to the analysis of asphaltenes. Copyright © 2016 John Wiley & Sons, Ltd

Performance evaluation of strip parquet flooring panels after long-term, in-service exposure

Due to its extraordinary hardness, decorative appearance and possible small dimensions, black locust wood is assumed to be an excellent material for strip parquetflooring. The favourable colour changes achieved by controlled steam treatment further increased the utilization potential of this material. Flooring was installed on a student dormitory stair landing in heavy use. Due to the flooring’s very high exposure, 5 years was considered a long enough period to compare the different face layer materials during in-service test. Oil was used as a coating to avoid the remarkable protecting effect of hard film-forming varnishes (acrylic, etc.) against abrasion. Besides the flooring turning grey (all face layers no matter what treatment), only some delamination occurred at certain places after five years in service.The laboratory test results for abrasion resistance, dimensional changes and deformation were analysed. Additionally, the Brinell-Mörath hardness after indoor service and the abrasion due to indoor service were analysed. In terms of abrasion resistance, dimensional changes and deformation, no essential differences werefound between the oil-treated and untreated black locust wood on the one hand, and the control oak specimen on the other. Long-term tests showed that, after 5 years in service, the Brinell-Mörath-hardness decreased considerably for all the testedmaterials. The type of section and the presence of wide rays influenced the roughness and the waviness of the surface after indoor service