The Experts below are selected from a list of 228 Experts worldwide ranked by ideXlab platform
Rafael Kandiyoti - One of the best experts on this subject based on the ideXlab platform.
-
The unusual properties of high Mass materials from coal-derived liquids☆
Fuel, 2003Co-Authors: C A Islas, Alan A. Herod, Isabel Suelves, W Li, T. J. Morgan, Rafael KandiyotiAbstract:Abstract This short paper highlights the unusual properties of the high-Mass material of coal liquids isolated by their insolubility in pyridine and solubility in NMP. The separation has been achieved by a column chromatography method. One gram quantity have been processed and near quantitative recovery of the sample as fractions has been achieved. This fractionation permitted recourse to a broad range of analytical methods, including some (e.g. 13 C NMR), which require Large sample sizes. Multiple macro analyses have been undertaken, using elemental analysis, TGA proximate analysis, NMR and FT-ir in addition to the micro-analytical methods used previously—pyrolysis-gc-ms, SEC, UV–fluorescence, probe-ms and MALDI-ms. The fractions show increasing concentrations of Large Molecular Mass material with increasing polarity of successive eluents used in the fractionation. Evidence from solid-state 13 C NMR and UV–fluorescence spectroscopy show progressive structural changes with increasing apparent Molecular Mass.
-
Pyrolysis of Baltic amber in a wire-mesh pyrolysis reactor: structural comparison of the tars with amber extracts in NMP
Journal of Analytical and Applied Pyrolysis, 2001Co-Authors: Suneerat Pipatmanomai, Alan A. Herod, C A Islas, Isabel Suelves, Denis R. Dugwell, Rafael KandiyotiAbstract:Abstract A sample of Baltic amber believed to be about 40 million years old, has been pyrolysed in a wire-mesh reactor. Nearly all (99%) of the sample was found to volatilise; the condensable tar yield was about 82%. These tars and extracts in 1-methyl-2-pyrrolidinone (NMP), ∼20% of the original amber sample, have been characterised by size exclusion chromatography (SEC) and UV-fluorescence spectroscopy (UV-F). Size exclusion chromatograms of the soluble fraction of the amber gave relatively low intensity signal, indicating the lack of strongly absorbing chromophores. The profiles of the pyrolysis tar were more intense, suggesting that the pyrolytic process promoted aromatisation of the original structures. SEC of the amber extracts showed the presence of apparently Large Molecular Mass material, possibly up to several million units. The SEC of the tar showed lower Molecular Mass material than that of the extract, with less absorbance at longer wavelengths, suggesting the presence of smaller polynuclear aromatic groups. Synchronous UV-fluorescence spectra suggest that the tar consisted mainly of fragmentation products of Larger Molecular Mass material, deriving mostly from the insoluble, probably partly cross-linked part of the original sample.
-
Size exclusion chromatography of soots and coal-derived materials with 1-methyl-2-pyrrolidinone as eluent : Observations on high Molecular Mass material
Energy & Fuels, 2000Co-Authors: Alan A. Herod, J. Shearman, María J. Lázaro, M Domin, Isabel Suelves, C. Dubau, R. Richaud, Jacqueline B. A. Card, A R Jones, Rafael KandiyotiAbstract:A number of samples which eluted at unexpectedly short retention times during size exclusion chromatography have been characterized. Soot and tar samples likely to show similar behavior have been examined. Distinct peaks from about 6 min were observed, compared to 9-10 min for more usual samples. Molecular Masses of the early eluting material appear to be Large, although extrapolation of existing calibrations does not seem appropriate. A naphthalene mesophase pitch also gave peaks at short elution times. It appears reasonable to interpret chromatograms of this nonpolar material as a direct indication of the presence of Large Molecular Mass material, and to infer that excluded peaks of SEC chromatograms do not necessarily result from the presence of clusters of polar molecules, GC-MS and probe-MS examination of the samples showed only very limited proportions of the samples to have small Molecular Masses. MALDI-MS spectra of the samples indicated the presence of signal up to 20 000 u. Taken together, data from SEC and the three MS techniques indicated the presence of very Large Molecular Mass materials in this set of samples. Tar deposits recovered from entrained, combusting coal particles have also been examined, providing direct evidence for the presence of Large Molecular Mass material in combustion environments. The observation contrasts with mathematical models of coal burners, where rates of combustion of volatiles are assumed similar to rates of combustion of methane. The nature of the early-eluting material is not known but repeated microfiltration and TEM indicate that it may correspond to Molecular diameters in the region of 20 nm. The soots and other samples appear to be in true solution rather than in colloidal suspension.
-
structural features of Large Molecular Mass material in coal derived liquids catalytic hydrocracking of the pyridine insoluble fraction of a coal tar pitch
European Journal of Mass Spectrometry, 2000Co-Authors: V Begon, María J. Lázaro, Alan A. Herod, C A Islas, I Suelves, D R Dugwell, Rafael KandiyotiAbstract:The pyridine-insoluble fraction of a coal-tar pitch has been catalytically hydrocracked. The starting sample contained no material that could be observed by gas chromatography/Mass spectrometry (GC/MS) or by heated-probe Mass spectrometry. The aim of the study was to generate structural information on this narrow cut of Large-Molecular-Mass material, which consisted mainly of compounds boiling above 450°C. A much broader boiling-point distribution was found for hydrocracked products; evidence from all analytical techniques used (size-exclusion chromatography, UV-fluorescence spectroscopy and heated-probe Mass spectrometry) indicated a significant reduction of the Molecular Mass range. A wide variety of aromatic groups was identified in hydrocracked products by heated-probe Mass spectrometry, ranging from phenanthrene (m/z 178) to beyond dibenzocoronene (m/z 400). Ions corresponding to alkyl (m/z 43, 57, 71 and 85) and alkenyl groups (m/z 41, 55, 69 and 83) were detected. The results reflect the ability of the hydrocracking process to cleave bonds within Large pitch molecules, releasing the structural units which form the molecules. The structure of the original pyridine-insoluble material may thus be seen as a series of aromatic groups linked by short bridges or small groups, but with some longer aliphatic bridges (C12 and C17) as shown by pyrolysis-GC/MS. Clearly, some Molecular species were reduced in Mass but still lay above the range of detection by heated-probe Mass spectrometry and could not be identified. Although the extent to which Large polycyclic aromatic entities themselves have been cracked (or otherwise reduced to smaller polycyclic aromatic groups) cannot be quantitatively discerned from the present data, the hydrocracking of isolated fractions of intractable coalderived material appears to offer a useful method for probing their structural features.
-
fractionation of a wood tar pitch by planar chromatography for the characterisation of Large Molecular Mass materials
Journal of Chromatography A, 1999Co-Authors: María J. Lázaro, Alan A. Herod, M Domin, Rafael KandiyotiAbstract:Abstract A commercial tar pitch derived from pine wood – Massen Pine (Pinus Massonia) and sold as Stockholm tar has been fractionated by planar chromatography with examination of the fractions by size exclusion chromatography in NMP eluent, by UV-fluorescence and by matrix assisted laser desorption Mass spectrometry. The relatively small molecules, mobile in planar chromatography, are shown to be non-polar. Large molecules were found in each fraction, corresponding in SEC elution times up to polystyrenes of Molecular Mass of at least 1.8 million. Size exclusion chromatography profiles by UV light absorbance showed differences in relative absorbance of different wavelengths for Large and small molecules, implying differences in structures. MALDI Mass spectra indicated molecules of Mass of several thousand Mass units with the upper limit of Mass not defined. Planar chromatography provides a fast, cheap method of isolating Large Molecular Mass fractions of this bioMass tar.
Alan A. Herod - One of the best experts on this subject based on the ideXlab platform.
-
The unusual properties of high Mass materials from coal-derived liquids☆
Fuel, 2003Co-Authors: C A Islas, Alan A. Herod, Isabel Suelves, W Li, T. J. Morgan, Rafael KandiyotiAbstract:Abstract This short paper highlights the unusual properties of the high-Mass material of coal liquids isolated by their insolubility in pyridine and solubility in NMP. The separation has been achieved by a column chromatography method. One gram quantity have been processed and near quantitative recovery of the sample as fractions has been achieved. This fractionation permitted recourse to a broad range of analytical methods, including some (e.g. 13 C NMR), which require Large sample sizes. Multiple macro analyses have been undertaken, using elemental analysis, TGA proximate analysis, NMR and FT-ir in addition to the micro-analytical methods used previously—pyrolysis-gc-ms, SEC, UV–fluorescence, probe-ms and MALDI-ms. The fractions show increasing concentrations of Large Molecular Mass material with increasing polarity of successive eluents used in the fractionation. Evidence from solid-state 13 C NMR and UV–fluorescence spectroscopy show progressive structural changes with increasing apparent Molecular Mass.
-
Pyrolysis of Baltic amber in a wire-mesh pyrolysis reactor: structural comparison of the tars with amber extracts in NMP
Journal of Analytical and Applied Pyrolysis, 2001Co-Authors: Suneerat Pipatmanomai, Alan A. Herod, C A Islas, Isabel Suelves, Denis R. Dugwell, Rafael KandiyotiAbstract:Abstract A sample of Baltic amber believed to be about 40 million years old, has been pyrolysed in a wire-mesh reactor. Nearly all (99%) of the sample was found to volatilise; the condensable tar yield was about 82%. These tars and extracts in 1-methyl-2-pyrrolidinone (NMP), ∼20% of the original amber sample, have been characterised by size exclusion chromatography (SEC) and UV-fluorescence spectroscopy (UV-F). Size exclusion chromatograms of the soluble fraction of the amber gave relatively low intensity signal, indicating the lack of strongly absorbing chromophores. The profiles of the pyrolysis tar were more intense, suggesting that the pyrolytic process promoted aromatisation of the original structures. SEC of the amber extracts showed the presence of apparently Large Molecular Mass material, possibly up to several million units. The SEC of the tar showed lower Molecular Mass material than that of the extract, with less absorbance at longer wavelengths, suggesting the presence of smaller polynuclear aromatic groups. Synchronous UV-fluorescence spectra suggest that the tar consisted mainly of fragmentation products of Larger Molecular Mass material, deriving mostly from the insoluble, probably partly cross-linked part of the original sample.
-
Size exclusion chromatography of soots and coal-derived materials with 1-methyl-2-pyrrolidinone as eluent : Observations on high Molecular Mass material
Energy & Fuels, 2000Co-Authors: Alan A. Herod, J. Shearman, María J. Lázaro, M Domin, Isabel Suelves, C. Dubau, R. Richaud, Jacqueline B. A. Card, A R Jones, Rafael KandiyotiAbstract:A number of samples which eluted at unexpectedly short retention times during size exclusion chromatography have been characterized. Soot and tar samples likely to show similar behavior have been examined. Distinct peaks from about 6 min were observed, compared to 9-10 min for more usual samples. Molecular Masses of the early eluting material appear to be Large, although extrapolation of existing calibrations does not seem appropriate. A naphthalene mesophase pitch also gave peaks at short elution times. It appears reasonable to interpret chromatograms of this nonpolar material as a direct indication of the presence of Large Molecular Mass material, and to infer that excluded peaks of SEC chromatograms do not necessarily result from the presence of clusters of polar molecules, GC-MS and probe-MS examination of the samples showed only very limited proportions of the samples to have small Molecular Masses. MALDI-MS spectra of the samples indicated the presence of signal up to 20 000 u. Taken together, data from SEC and the three MS techniques indicated the presence of very Large Molecular Mass materials in this set of samples. Tar deposits recovered from entrained, combusting coal particles have also been examined, providing direct evidence for the presence of Large Molecular Mass material in combustion environments. The observation contrasts with mathematical models of coal burners, where rates of combustion of volatiles are assumed similar to rates of combustion of methane. The nature of the early-eluting material is not known but repeated microfiltration and TEM indicate that it may correspond to Molecular diameters in the region of 20 nm. The soots and other samples appear to be in true solution rather than in colloidal suspension.
-
structural features of Large Molecular Mass material in coal derived liquids catalytic hydrocracking of the pyridine insoluble fraction of a coal tar pitch
European Journal of Mass Spectrometry, 2000Co-Authors: V Begon, María J. Lázaro, Alan A. Herod, C A Islas, I Suelves, D R Dugwell, Rafael KandiyotiAbstract:The pyridine-insoluble fraction of a coal-tar pitch has been catalytically hydrocracked. The starting sample contained no material that could be observed by gas chromatography/Mass spectrometry (GC/MS) or by heated-probe Mass spectrometry. The aim of the study was to generate structural information on this narrow cut of Large-Molecular-Mass material, which consisted mainly of compounds boiling above 450°C. A much broader boiling-point distribution was found for hydrocracked products; evidence from all analytical techniques used (size-exclusion chromatography, UV-fluorescence spectroscopy and heated-probe Mass spectrometry) indicated a significant reduction of the Molecular Mass range. A wide variety of aromatic groups was identified in hydrocracked products by heated-probe Mass spectrometry, ranging from phenanthrene (m/z 178) to beyond dibenzocoronene (m/z 400). Ions corresponding to alkyl (m/z 43, 57, 71 and 85) and alkenyl groups (m/z 41, 55, 69 and 83) were detected. The results reflect the ability of the hydrocracking process to cleave bonds within Large pitch molecules, releasing the structural units which form the molecules. The structure of the original pyridine-insoluble material may thus be seen as a series of aromatic groups linked by short bridges or small groups, but with some longer aliphatic bridges (C12 and C17) as shown by pyrolysis-GC/MS. Clearly, some Molecular species were reduced in Mass but still lay above the range of detection by heated-probe Mass spectrometry and could not be identified. Although the extent to which Large polycyclic aromatic entities themselves have been cracked (or otherwise reduced to smaller polycyclic aromatic groups) cannot be quantitatively discerned from the present data, the hydrocracking of isolated fractions of intractable coalderived material appears to offer a useful method for probing their structural features.
-
fractionation of a wood tar pitch by planar chromatography for the characterisation of Large Molecular Mass materials
Journal of Chromatography A, 1999Co-Authors: María J. Lázaro, Alan A. Herod, M Domin, Rafael KandiyotiAbstract:Abstract A commercial tar pitch derived from pine wood – Massen Pine (Pinus Massonia) and sold as Stockholm tar has been fractionated by planar chromatography with examination of the fractions by size exclusion chromatography in NMP eluent, by UV-fluorescence and by matrix assisted laser desorption Mass spectrometry. The relatively small molecules, mobile in planar chromatography, are shown to be non-polar. Large molecules were found in each fraction, corresponding in SEC elution times up to polystyrenes of Molecular Mass of at least 1.8 million. Size exclusion chromatography profiles by UV light absorbance showed differences in relative absorbance of different wavelengths for Large and small molecules, implying differences in structures. MALDI Mass spectra indicated molecules of Mass of several thousand Mass units with the upper limit of Mass not defined. Planar chromatography provides a fast, cheap method of isolating Large Molecular Mass fractions of this bioMass tar.
María J. Lázaro - One of the best experts on this subject based on the ideXlab platform.
-
Size exclusion chromatography of soots and coal-derived materials with 1-methyl-2-pyrrolidinone as eluent : Observations on high Molecular Mass material
Energy & Fuels, 2000Co-Authors: Alan A. Herod, J. Shearman, María J. Lázaro, M Domin, Isabel Suelves, C. Dubau, R. Richaud, Jacqueline B. A. Card, A R Jones, Rafael KandiyotiAbstract:A number of samples which eluted at unexpectedly short retention times during size exclusion chromatography have been characterized. Soot and tar samples likely to show similar behavior have been examined. Distinct peaks from about 6 min were observed, compared to 9-10 min for more usual samples. Molecular Masses of the early eluting material appear to be Large, although extrapolation of existing calibrations does not seem appropriate. A naphthalene mesophase pitch also gave peaks at short elution times. It appears reasonable to interpret chromatograms of this nonpolar material as a direct indication of the presence of Large Molecular Mass material, and to infer that excluded peaks of SEC chromatograms do not necessarily result from the presence of clusters of polar molecules, GC-MS and probe-MS examination of the samples showed only very limited proportions of the samples to have small Molecular Masses. MALDI-MS spectra of the samples indicated the presence of signal up to 20 000 u. Taken together, data from SEC and the three MS techniques indicated the presence of very Large Molecular Mass materials in this set of samples. Tar deposits recovered from entrained, combusting coal particles have also been examined, providing direct evidence for the presence of Large Molecular Mass material in combustion environments. The observation contrasts with mathematical models of coal burners, where rates of combustion of volatiles are assumed similar to rates of combustion of methane. The nature of the early-eluting material is not known but repeated microfiltration and TEM indicate that it may correspond to Molecular diameters in the region of 20 nm. The soots and other samples appear to be in true solution rather than in colloidal suspension.
-
structural features of Large Molecular Mass material in coal derived liquids catalytic hydrocracking of the pyridine insoluble fraction of a coal tar pitch
European Journal of Mass Spectrometry, 2000Co-Authors: V Begon, María J. Lázaro, Alan A. Herod, C A Islas, I Suelves, D R Dugwell, Rafael KandiyotiAbstract:The pyridine-insoluble fraction of a coal-tar pitch has been catalytically hydrocracked. The starting sample contained no material that could be observed by gas chromatography/Mass spectrometry (GC/MS) or by heated-probe Mass spectrometry. The aim of the study was to generate structural information on this narrow cut of Large-Molecular-Mass material, which consisted mainly of compounds boiling above 450°C. A much broader boiling-point distribution was found for hydrocracked products; evidence from all analytical techniques used (size-exclusion chromatography, UV-fluorescence spectroscopy and heated-probe Mass spectrometry) indicated a significant reduction of the Molecular Mass range. A wide variety of aromatic groups was identified in hydrocracked products by heated-probe Mass spectrometry, ranging from phenanthrene (m/z 178) to beyond dibenzocoronene (m/z 400). Ions corresponding to alkyl (m/z 43, 57, 71 and 85) and alkenyl groups (m/z 41, 55, 69 and 83) were detected. The results reflect the ability of the hydrocracking process to cleave bonds within Large pitch molecules, releasing the structural units which form the molecules. The structure of the original pyridine-insoluble material may thus be seen as a series of aromatic groups linked by short bridges or small groups, but with some longer aliphatic bridges (C12 and C17) as shown by pyrolysis-GC/MS. Clearly, some Molecular species were reduced in Mass but still lay above the range of detection by heated-probe Mass spectrometry and could not be identified. Although the extent to which Large polycyclic aromatic entities themselves have been cracked (or otherwise reduced to smaller polycyclic aromatic groups) cannot be quantitatively discerned from the present data, the hydrocracking of isolated fractions of intractable coalderived material appears to offer a useful method for probing their structural features.
-
fractionation of a wood tar pitch by planar chromatography for the characterisation of Large Molecular Mass materials
Journal of Chromatography A, 1999Co-Authors: María J. Lázaro, Alan A. Herod, M Domin, Rafael KandiyotiAbstract:Abstract A commercial tar pitch derived from pine wood – Massen Pine (Pinus Massonia) and sold as Stockholm tar has been fractionated by planar chromatography with examination of the fractions by size exclusion chromatography in NMP eluent, by UV-fluorescence and by matrix assisted laser desorption Mass spectrometry. The relatively small molecules, mobile in planar chromatography, are shown to be non-polar. Large molecules were found in each fraction, corresponding in SEC elution times up to polystyrenes of Molecular Mass of at least 1.8 million. Size exclusion chromatography profiles by UV light absorbance showed differences in relative absorbance of different wavelengths for Large and small molecules, implying differences in structures. MALDI Mass spectra indicated molecules of Mass of several thousand Mass units with the upper limit of Mass not defined. Planar chromatography provides a fast, cheap method of isolating Large Molecular Mass fractions of this bioMass tar.
-
Large Molecular Mass materials in coal derived liquids by 252cf plasma and matrix assisted laser desorption Mass spectrometry
Energy & Fuels, 1998Co-Authors: M Domin, María J. Lázaro, Alan A. Herod, Shang Li, John W Larsen, Rafael KandiyotiAbstract:The paper compares responses of 252Cf-plasma desorption MS (PD-MS) and matrix-assisted laser desorption (MALDI) MS to identical samples. The two pairs of samples selected for the comparison were known from previous work to differ significantly in their high Mass contents. MALDI-MS showed Large differences in MM distributions within both pairs of samples. The PD-MS data showed a degree of similarity between one pair of samples (pyridine soluble/insoluble fractions of a coal tar pitch); for the second pair (a coal extract and its hydrocracked product), trends from the two MS techniques agreed closely. The MM range observed by PD-MS was somewhat narrower, extending to between 3000 and 5000 u. Significant differences within pairs of samples were observed by SEC and by UV-fluorescence spectroscopy, providing somewhat closer agreement with the MALDI spectra. The two MS instruments differ in two important respects: the ionization system (i.e., plasma vs laser desorption) and the maximum available ion extraction...
-
Effect of LiBr addition to 1-methyl-2-pyrrolidinone in the size-exclusion chromatography of coal-derived materials
Energy and Fuels, 1998Co-Authors: Alan A. Herod, J. Shearman, Keith D. Bartle, María J. Lázaro, B.r. Johnson, Rafael KandiyotiAbstract:Two propositions relating to the interpretation of size-exclusion chromatograms (SEC) of coal-derived materials in 1-methyl-2-pyrrolidinone (NMP) have been examined. These were (i) that signal peaks showing up at exclusion (short retention time) limits of SEC columns are due to sample polarity alone and (ii) that shifts in SEC chromatograms to longer retention times, observed upon addition of LiBr to the eluent(NMP), are due to dissipation of ionic binding forces, causing disaggregation of polar clusters that would otherwise have appeared at retention times appropriate to Larger Molecular Masses. In our experiments, effects due to polarity and Molecular Mass have been isolated by using two nonpolar samples (a naphthalene mesophase pitch and a mixture of fullerenes). In the presence of LiBr, precipitation of solute out of solution and shifts of chromatograms to longer retention times, unrelated to sample polarity, have been observed. A partial breakdown of the size exclusion mechanism was identified by the observed extension of chromatograms beyond the permeation limit of the column, similar to those observed when using eluents of insufficient solvent strength (e.g., THF, chloroform). Dosing LiBr into NMP sharply reduces the solvent power of NMP for coal-derived solutes. In the absence of LiBr, SEC chromatograms of the fullerene mixture, the naphthalene mesophase pitch, and its fractions separated by planar chromatography clearly showed significant signal under the "excluded" peak, entirely due to nonpolar material. The damage caused to the SEC column arising from precipitation of sample, in the presence of LiBr, was not permanent as had originally been feared. The balance of the evidence suggests that polarity of some molecules may cause shifts in their elution times to shorter values (Larger apparent Molecular Masses) and that these may overlap with signal from Large Molecular Mass material.
M Domin - One of the best experts on this subject based on the ideXlab platform.
-
Size exclusion chromatography of soots and coal-derived materials with 1-methyl-2-pyrrolidinone as eluent : Observations on high Molecular Mass material
Energy & Fuels, 2000Co-Authors: Alan A. Herod, J. Shearman, María J. Lázaro, M Domin, Isabel Suelves, C. Dubau, R. Richaud, Jacqueline B. A. Card, A R Jones, Rafael KandiyotiAbstract:A number of samples which eluted at unexpectedly short retention times during size exclusion chromatography have been characterized. Soot and tar samples likely to show similar behavior have been examined. Distinct peaks from about 6 min were observed, compared to 9-10 min for more usual samples. Molecular Masses of the early eluting material appear to be Large, although extrapolation of existing calibrations does not seem appropriate. A naphthalene mesophase pitch also gave peaks at short elution times. It appears reasonable to interpret chromatograms of this nonpolar material as a direct indication of the presence of Large Molecular Mass material, and to infer that excluded peaks of SEC chromatograms do not necessarily result from the presence of clusters of polar molecules, GC-MS and probe-MS examination of the samples showed only very limited proportions of the samples to have small Molecular Masses. MALDI-MS spectra of the samples indicated the presence of signal up to 20 000 u. Taken together, data from SEC and the three MS techniques indicated the presence of very Large Molecular Mass materials in this set of samples. Tar deposits recovered from entrained, combusting coal particles have also been examined, providing direct evidence for the presence of Large Molecular Mass material in combustion environments. The observation contrasts with mathematical models of coal burners, where rates of combustion of volatiles are assumed similar to rates of combustion of methane. The nature of the early-eluting material is not known but repeated microfiltration and TEM indicate that it may correspond to Molecular diameters in the region of 20 nm. The soots and other samples appear to be in true solution rather than in colloidal suspension.
-
fractionation of a wood tar pitch by planar chromatography for the characterisation of Large Molecular Mass materials
Journal of Chromatography A, 1999Co-Authors: María J. Lázaro, Alan A. Herod, M Domin, Rafael KandiyotiAbstract:Abstract A commercial tar pitch derived from pine wood – Massen Pine (Pinus Massonia) and sold as Stockholm tar has been fractionated by planar chromatography with examination of the fractions by size exclusion chromatography in NMP eluent, by UV-fluorescence and by matrix assisted laser desorption Mass spectrometry. The relatively small molecules, mobile in planar chromatography, are shown to be non-polar. Large molecules were found in each fraction, corresponding in SEC elution times up to polystyrenes of Molecular Mass of at least 1.8 million. Size exclusion chromatography profiles by UV light absorbance showed differences in relative absorbance of different wavelengths for Large and small molecules, implying differences in structures. MALDI Mass spectra indicated molecules of Mass of several thousand Mass units with the upper limit of Mass not defined. Planar chromatography provides a fast, cheap method of isolating Large Molecular Mass fractions of this bioMass tar.
-
Large Molecular Mass materials in coal derived liquids by 252cf plasma and matrix assisted laser desorption Mass spectrometry
Energy & Fuels, 1998Co-Authors: M Domin, María J. Lázaro, Alan A. Herod, Shang Li, John W Larsen, Rafael KandiyotiAbstract:The paper compares responses of 252Cf-plasma desorption MS (PD-MS) and matrix-assisted laser desorption (MALDI) MS to identical samples. The two pairs of samples selected for the comparison were known from previous work to differ significantly in their high Mass contents. MALDI-MS showed Large differences in MM distributions within both pairs of samples. The PD-MS data showed a degree of similarity between one pair of samples (pyridine soluble/insoluble fractions of a coal tar pitch); for the second pair (a coal extract and its hydrocracked product), trends from the two MS techniques agreed closely. The MM range observed by PD-MS was somewhat narrower, extending to between 3000 and 5000 u. Significant differences within pairs of samples were observed by SEC and by UV-fluorescence spectroscopy, providing somewhat closer agreement with the MALDI spectra. The two MS instruments differ in two important respects: the ionization system (i.e., plasma vs laser desorption) and the maximum available ion extraction...
John E Parker - One of the best experts on this subject based on the ideXlab platform.
-
identification of Large Molecular Mass material in high temperature coal tars and pitches by laser desorption Mass spectroscopy
Fuel, 1993Co-Authors: John E Parker, Alan A. Herod, C A F Johnson, Philip John, Gerry P Smith, Brian J Stokes, Rafael KandiyotiAbstract:Abstract Molecular Masses of up to 12 000 Da have been identified by laser desorption Mass spectroscopy (l.d.-m.s.) in a number of coal tars and extracts. Observed Molecular Masses were greater than any hitherto detected in coal-derived liquids; fractions of high temperature coke oven tars have been used for verification of initial findings. Low Molecular Mass materials have been analysed using similar experimental procedures, to confirm the absence of laser or other apparatus derived high Molecular Mass clusters. Spectra extending to 12 000 Da show an envelope between 1000 and 3000 Da and a low Molecular Mass envelope between 12 and 400 Da, the latter apparently indicating the presence of carbon clusters. At high laser power densities, the 1000 to 3000 Da envelope was observed to lose intensity, with parallel gain in intensity of the low Mass carbon cluster envelope, suggesting increased breakdown of substrate molecules under increasing laser power density. Comparisons with results from g.c.-m.s. and probe m.s. are presented, showing Masses up to 600 Da. Limited structural information about the Large Molecular Mass materials can be inferred from the present results, suggesting the presence of small aromatic groups with Mass differences corresponding to methyl groups, ethylene bridges and benzo groups.
