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Rafael Kandiyoti - One of the best experts on this subject based on the ideXlab platform.
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positive ion electrospray ionisation mass spectrometry of acetone and acetonitrile soluble fractions of Coal Derived Liquids
European Journal of Mass Spectrometry, 2005Co-Authors: Alan A. Herod, Marcos Millan, Trevor J Morgan, Jie Feng, Rafael KandiyotiAbstract:The acetone-soluble fraction of a Coal tar pitch has been examined using positive ion electrospray ionisation (ESI), by infusion into the ESI stream. The acetonitrile-soluble fractions of a Coal tar pitch, a Coal digest and a low temperature Coal tar have also been studied by high performance liquid chromatography/ESI mass spectrometry. In contrast to positive-ion ESI of proteins, which gives rise to multiply charged ions, this application to fossil fuels, petroleum asphaltenes and humic acids, appears to only give singly-charged ions. The major components of these samples, polycyclic aromatics that could be detected by gas chromatography/mass spectrometry, formed no ions in positive-ion ESI. The only ions detected were formed from azaarenes. Ions up to only m/z 500 or so were detected, although these fractions are known to contain higher-mass species, up to at least several thousand mass units. Fractions of the three samples [Coal tar pitch, Coal digest and a low temperature Coal tar], insoluble in aceto...
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The unusual properties of high mass materials from Coal-Derived Liquids☆
Fuel, 2003Co-Authors: C A Islas, T. J. Morgan, Isabel Suelves, Alan A. Herod, W. Li, 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.
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trace elements in Coal Derived Liquids analysis by icp ms and mossbauer spectroscopy
Fuel, 2000Co-Authors: R Richaud, Alan A. Herod, H Lachas, M J Lazaro, Leon J Clarke, K E Jarvis, Terence C Gibb, Rafael KandiyotiAbstract:Concentrations of trace elements in Coal Derived Liquids have been investigated by inductively coupled plasma-mass spectrometry (ICP-MS) and by Mossbauer spectroscopy. Liquefaction extracts prepared from the Argonne Premium Coals and a Coal tar pitch have been examined. Microwave digestion in concentrated nitric acid has been shown as a suitable method for determining trace element concentrations in Coal Derived Liquids by ICP-MS—for sample sizes as small as 3–20 mg. High concentrations of Fe were found for all extract samples (<265–1474 ppm). Ti, Cr, Mn, Co, Ga, Sb, Cs and Ba were measurable. Concentration distributions of trace elements found in the extracts bore little relation to the corresponding distributions in the original Coals. The proportions of individual trace elements present in the original Coals and found in the extracts, varied widely. Mossbauer spectroscopy of the extracts indicated that the high Fe-concentrations corresponded to the presence of organometallic-Fe compounds—and not to pyritic iron. There is evidence suggesting the presence of material Derived from iron-storage proteins such as ferritin, but final proof is lacking. Our data suggest that other metallic ions detected in these Coal Derived Liquids may be present in association with the organic material. Concentrations of paramagnetic metal species were found to be of the same order of magnitude as ESR spin-densities already found in Coal Liquids. Both types of paramagnetic species are suspected of causing loss of signal in solid state 13C NMR.
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planar chromatographic separation of petroleum residues and Coal Derived Liquids
Journal of Chromatography A, 1999Co-Authors: J P Deelchand, Alan A. Herod, M J Lazaro, Z Naqvi, C Dubau, J Shearman, H Read, Rafael KandiyotiAbstract:Abstract Vacuum distillation residues from two petroleum crudes, a Coal liquefaction extract and a Coal tar pitch have been fractionated by planar chromatography (PC) using two solvent sequences: pyridine–acetonitrile and tetrahydrofuran (THF)–toluene. Fractions recovered from PC were examined by UV-fluorescence spectroscopy (UV-F), size-exclusion chromatography (SEC). UV-F and SEC of the whole samples showed differences in aromatic cluster size and molecular mass (MM) ranges which could be related to the different origins of the samples. The MM ranges indicated by SEC were greater for the vacuum residues than for Coal-Derived materials. However, the UV-F spectra of the fractions indicated that the petroleum residue fractions contained similar aromatic types, whereas the fractions from Coal Liquids contained significantly different aromatic types. SEC profiles of the fractions indicated a separation of Coal-Derived samples by increasing molecular size with increasing immobility in PC, whereas for petroleum fractions, the same trend was not apparent. MALDI-mass spectra of the set of original samples showed broadly similar ranges of MM distributions but additional work is necessary to identify appropriate matrices and procedures in order to improve the MALDI spectra.
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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, John W. Larsen, Shang Li, 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...
Alan A. Herod - One of the best experts on this subject based on the ideXlab platform.
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positive ion electrospray ionisation mass spectrometry of acetone and acetonitrile soluble fractions of Coal Derived Liquids
European Journal of Mass Spectrometry, 2005Co-Authors: Alan A. Herod, Marcos Millan, Trevor J Morgan, Jie Feng, Rafael KandiyotiAbstract:The acetone-soluble fraction of a Coal tar pitch has been examined using positive ion electrospray ionisation (ESI), by infusion into the ESI stream. The acetonitrile-soluble fractions of a Coal tar pitch, a Coal digest and a low temperature Coal tar have also been studied by high performance liquid chromatography/ESI mass spectrometry. In contrast to positive-ion ESI of proteins, which gives rise to multiply charged ions, this application to fossil fuels, petroleum asphaltenes and humic acids, appears to only give singly-charged ions. The major components of these samples, polycyclic aromatics that could be detected by gas chromatography/mass spectrometry, formed no ions in positive-ion ESI. The only ions detected were formed from azaarenes. Ions up to only m/z 500 or so were detected, although these fractions are known to contain higher-mass species, up to at least several thousand mass units. Fractions of the three samples [Coal tar pitch, Coal digest and a low temperature Coal tar], insoluble in aceto...
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The unusual properties of high mass materials from Coal-Derived Liquids☆
Fuel, 2003Co-Authors: C A Islas, T. J. Morgan, Isabel Suelves, Alan A. Herod, W. Li, 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.
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Molecular mass distributions and structural characterisation of Coal Derived Liquids
Fuel, 2000Co-Authors: Alan A. HerodAbstract:Calibration data for size exclusion chromatography and results from the analysis of MALDI–TOF mass-spectra of Coal Derived Liquids have been presented. The work provides the means for obtaining much more quantitative information from these two techniques than has hitherto been possible. The polystyrene based calibration has been matched against elution times of a wide range of model compounds (PAH, azaarenes, other nitrogen bearing compounds, several dyes, polars and numerous oxygenated compounds), covering a molecular mass range up to 1086u. Compounds in all groups appeared to elute with a predominantly size dependent mechanism. With the exception of the somewhat atypical fullerene mixture, none of the model compounds eluted at times so early as to be detected in the excluded region of the chromatogram (i.e. near 10.5min). Several semi-quantitative methods have been used to establish the upper mass limit of corresponding MALDI–TOF mass-spectra, which can be safely considered as representing signal. Spectra of a Coal tar pitch and its pyridine insoluble fraction were analysed. The highest estimates of the high mass limits based on the calculation of number and weight average parameters was >300,000u. A conservative estimate obtained with a new method based on subtracting multiples of the standard deviation from the signal gave 42,000 and 95,600u, for the two samples, respectively. Fractions of the same Coal tar pitch (separated by planar chromatography) have been characterised, to test for changes in structural features with changing MM-distributions. SEC and MALDI–TOF–MS showed decreasing MM-distributions with increasing mobility in planar chromatography. However, 13C NMR and pyrolysis–GC–MS showed that the immobile fraction contained greater proportions of aliphatic material compared to more mobile fractions. The mobile material consists of the aromatic systems normally associated with Coal tar. The relatively immobile (larger-MM) fractions consisted of aromatic systems too large to elute through the chromatographic column (in pyrolysis–GC–MS) and linked together by aliphatic chains, which were released on pyrolysis and detected as major pyrolysis products.
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trace elements in Coal Derived Liquids analysis by icp ms and mossbauer spectroscopy
Fuel, 2000Co-Authors: R Richaud, Alan A. Herod, H Lachas, M J Lazaro, Leon J Clarke, K E Jarvis, Terence C Gibb, Rafael KandiyotiAbstract:Concentrations of trace elements in Coal Derived Liquids have been investigated by inductively coupled plasma-mass spectrometry (ICP-MS) and by Mossbauer spectroscopy. Liquefaction extracts prepared from the Argonne Premium Coals and a Coal tar pitch have been examined. Microwave digestion in concentrated nitric acid has been shown as a suitable method for determining trace element concentrations in Coal Derived Liquids by ICP-MS—for sample sizes as small as 3–20 mg. High concentrations of Fe were found for all extract samples (<265–1474 ppm). Ti, Cr, Mn, Co, Ga, Sb, Cs and Ba were measurable. Concentration distributions of trace elements found in the extracts bore little relation to the corresponding distributions in the original Coals. The proportions of individual trace elements present in the original Coals and found in the extracts, varied widely. Mossbauer spectroscopy of the extracts indicated that the high Fe-concentrations corresponded to the presence of organometallic-Fe compounds—and not to pyritic iron. There is evidence suggesting the presence of material Derived from iron-storage proteins such as ferritin, but final proof is lacking. Our data suggest that other metallic ions detected in these Coal Derived Liquids may be present in association with the organic material. Concentrations of paramagnetic metal species were found to be of the same order of magnitude as ESR spin-densities already found in Coal Liquids. Both types of paramagnetic species are suspected of causing loss of signal in solid state 13C NMR.
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planar chromatographic separation of petroleum residues and Coal Derived Liquids
Journal of Chromatography A, 1999Co-Authors: J P Deelchand, Alan A. Herod, M J Lazaro, Z Naqvi, C Dubau, J Shearman, H Read, Rafael KandiyotiAbstract:Abstract Vacuum distillation residues from two petroleum crudes, a Coal liquefaction extract and a Coal tar pitch have been fractionated by planar chromatography (PC) using two solvent sequences: pyridine–acetonitrile and tetrahydrofuran (THF)–toluene. Fractions recovered from PC were examined by UV-fluorescence spectroscopy (UV-F), size-exclusion chromatography (SEC). UV-F and SEC of the whole samples showed differences in aromatic cluster size and molecular mass (MM) ranges which could be related to the different origins of the samples. The MM ranges indicated by SEC were greater for the vacuum residues than for Coal-Derived materials. However, the UV-F spectra of the fractions indicated that the petroleum residue fractions contained similar aromatic types, whereas the fractions from Coal Liquids contained significantly different aromatic types. SEC profiles of the fractions indicated a separation of Coal-Derived samples by increasing molecular size with increasing immobility in PC, whereas for petroleum fractions, the same trend was not apparent. MALDI-mass spectra of the set of original samples showed broadly similar ranges of MM distributions but additional work is necessary to identify appropriate matrices and procedures in order to improve the MALDI spectra.
M. Domin - One of the best experts on this subject based on the ideXlab platform.
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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, John W. Larsen, Shang Li, 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...
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effect of polydispersity on the characterization of Coal Derived Liquids by matrix assisted laser desorption ionization time of flight mass spectrometry inferences from results for mixtures of polystyrene molecular mass standards
Rapid Communications in Mass Spectrometry, 1997Co-Authors: M. Domin, Alan A. Herod, M J Lazaro, R Moreea, Rafael KandiyotiAbstract:Seven polystyrene molecular mass standards have been run in matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) singly, in pairs, in groups of three and as a mixture of the seven distinct samples. All standards had polydispersities of near unity. When run singly or in pairs, MALDI-spectra of all standard polymer samples could be observed clearly and showed approximately equal areas. Mixtures of multiple standards have been run at variable ion extraction voltages: when the voltage was reduced below 25 kV, low molar mass samples tended to predominate in the spectra, at the expense of the higher molar mass standards. Peaks due to the high mass standards were still observable above the noise level, but (for equimolar mixtures) areas under the peaks were no longer comparable. With the full set of seven samples, discrimination against intensities of the higher mass standards could be clearly observed, even at the highest ion extraction voltage available (30 kV). With increasing ion extraction voltage the MALDI-spectra of a Coal tar pitch and its tetrahydrofuran-insoluble fraction showed increasing intensities of higher mass ranges. Due to the wide polydispersity of Coal Derived samples, MALDI-spectra would be expected to severely underestimate the proportion of high mass materials present. Further work on mixtures of different types of polymer standards would clearly be useful; for Coal Derived Liquids, more extensive fractionation than that used here would seem advisable in order to reduce sample polydispersity. © 1997 John Wiley & Sons, Ltd.
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molecular mass determinations in Coal Derived Liquids by maldi mass spectrometry and size exclusion chromatography
Fuel, 1997Co-Authors: M J Lazaro, M. Domin, Alan A. Herod, Mike Cocksedge, Rafael KandiyotiAbstract:Abstract This study examined the effect of changes in instrument-related parameters on mass spectra obtained by MALDI-m.s.: ion-extraction voltage, laser power and sample loading. Results were compared with those of size-exclusion chromatography (s.e.c.) using 1-methyl-2-pyrrolidinone as mobile phase. A Coal tar pitch and its pyridine-soluble and pyridine-insoluble fractions were used as samples. MALDI-mass spectra were obtained with no added matrix, since the sample absorbed strongly at the laser wavelength, 337 nm. Higher extraction voltages (up to 30 kV) led to the observation of higher masses in the whole pitch and its pyridine-insoluble fraction, where the presence of higher-molecular-mass material was indicated by s.e.c. Increasing the ion extraction voltage served only to accelerate species already ionized, without otherwise disturbing the sample: the use of higher ion extraction voltages must be therefore be considered as providing a more complete inventory of already ionized species. Increasing the laser power level and sample loading on the target led to similar changes in the spectra, although there were indications that for both these parameters, the results might no longer improve (and might eventually deteriorate) beyond optimum values, which appear to be sample-dependent. The low-power spectra revealed more structural information at low masses, where series of homologous peaks could be observed, compared with the spectra at high power.
M J Lazaro - One of the best experts on this subject based on the ideXlab platform.
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trace elements in Coal Derived Liquids analysis by icp ms and mossbauer spectroscopy
Fuel, 2000Co-Authors: R Richaud, Alan A. Herod, H Lachas, M J Lazaro, Leon J Clarke, K E Jarvis, Terence C Gibb, Rafael KandiyotiAbstract:Concentrations of trace elements in Coal Derived Liquids have been investigated by inductively coupled plasma-mass spectrometry (ICP-MS) and by Mossbauer spectroscopy. Liquefaction extracts prepared from the Argonne Premium Coals and a Coal tar pitch have been examined. Microwave digestion in concentrated nitric acid has been shown as a suitable method for determining trace element concentrations in Coal Derived Liquids by ICP-MS—for sample sizes as small as 3–20 mg. High concentrations of Fe were found for all extract samples (<265–1474 ppm). Ti, Cr, Mn, Co, Ga, Sb, Cs and Ba were measurable. Concentration distributions of trace elements found in the extracts bore little relation to the corresponding distributions in the original Coals. The proportions of individual trace elements present in the original Coals and found in the extracts, varied widely. Mossbauer spectroscopy of the extracts indicated that the high Fe-concentrations corresponded to the presence of organometallic-Fe compounds—and not to pyritic iron. There is evidence suggesting the presence of material Derived from iron-storage proteins such as ferritin, but final proof is lacking. Our data suggest that other metallic ions detected in these Coal Derived Liquids may be present in association with the organic material. Concentrations of paramagnetic metal species were found to be of the same order of magnitude as ESR spin-densities already found in Coal Liquids. Both types of paramagnetic species are suspected of causing loss of signal in solid state 13C NMR.
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planar chromatographic separation of petroleum residues and Coal Derived Liquids
Journal of Chromatography A, 1999Co-Authors: J P Deelchand, Alan A. Herod, M J Lazaro, Z Naqvi, C Dubau, J Shearman, H Read, Rafael KandiyotiAbstract:Abstract Vacuum distillation residues from two petroleum crudes, a Coal liquefaction extract and a Coal tar pitch have been fractionated by planar chromatography (PC) using two solvent sequences: pyridine–acetonitrile and tetrahydrofuran (THF)–toluene. Fractions recovered from PC were examined by UV-fluorescence spectroscopy (UV-F), size-exclusion chromatography (SEC). UV-F and SEC of the whole samples showed differences in aromatic cluster size and molecular mass (MM) ranges which could be related to the different origins of the samples. The MM ranges indicated by SEC were greater for the vacuum residues than for Coal-Derived materials. However, the UV-F spectra of the fractions indicated that the petroleum residue fractions contained similar aromatic types, whereas the fractions from Coal Liquids contained significantly different aromatic types. SEC profiles of the fractions indicated a separation of Coal-Derived samples by increasing molecular size with increasing immobility in PC, whereas for petroleum fractions, the same trend was not apparent. MALDI-mass spectra of the set of original samples showed broadly similar ranges of MM distributions but additional work is necessary to identify appropriate matrices and procedures in order to improve the MALDI spectra.
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effect of polydispersity on the characterization of Coal Derived Liquids by matrix assisted laser desorption ionization time of flight mass spectrometry inferences from results for mixtures of polystyrene molecular mass standards
Rapid Communications in Mass Spectrometry, 1997Co-Authors: M. Domin, Alan A. Herod, M J Lazaro, R Moreea, Rafael KandiyotiAbstract:Seven polystyrene molecular mass standards have been run in matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) singly, in pairs, in groups of three and as a mixture of the seven distinct samples. All standards had polydispersities of near unity. When run singly or in pairs, MALDI-spectra of all standard polymer samples could be observed clearly and showed approximately equal areas. Mixtures of multiple standards have been run at variable ion extraction voltages: when the voltage was reduced below 25 kV, low molar mass samples tended to predominate in the spectra, at the expense of the higher molar mass standards. Peaks due to the high mass standards were still observable above the noise level, but (for equimolar mixtures) areas under the peaks were no longer comparable. With the full set of seven samples, discrimination against intensities of the higher mass standards could be clearly observed, even at the highest ion extraction voltage available (30 kV). With increasing ion extraction voltage the MALDI-spectra of a Coal tar pitch and its tetrahydrofuran-insoluble fraction showed increasing intensities of higher mass ranges. Due to the wide polydispersity of Coal Derived samples, MALDI-spectra would be expected to severely underestimate the proportion of high mass materials present. Further work on mixtures of different types of polymer standards would clearly be useful; for Coal Derived Liquids, more extensive fractionation than that used here would seem advisable in order to reduce sample polydispersity. © 1997 John Wiley & Sons, Ltd.
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molecular mass determinations in Coal Derived Liquids by maldi mass spectrometry and size exclusion chromatography
Fuel, 1997Co-Authors: M J Lazaro, M. Domin, Alan A. Herod, Mike Cocksedge, Rafael KandiyotiAbstract:Abstract This study examined the effect of changes in instrument-related parameters on mass spectra obtained by MALDI-m.s.: ion-extraction voltage, laser power and sample loading. Results were compared with those of size-exclusion chromatography (s.e.c.) using 1-methyl-2-pyrrolidinone as mobile phase. A Coal tar pitch and its pyridine-soluble and pyridine-insoluble fractions were used as samples. MALDI-mass spectra were obtained with no added matrix, since the sample absorbed strongly at the laser wavelength, 337 nm. Higher extraction voltages (up to 30 kV) led to the observation of higher masses in the whole pitch and its pyridine-insoluble fraction, where the presence of higher-molecular-mass material was indicated by s.e.c. Increasing the ion extraction voltage served only to accelerate species already ionized, without otherwise disturbing the sample: the use of higher ion extraction voltages must be therefore be considered as providing a more complete inventory of already ionized species. Increasing the laser power level and sample loading on the target led to similar changes in the spectra, although there were indications that for both these parameters, the results might no longer improve (and might eventually deteriorate) beyond optimum values, which appear to be sample-dependent. The low-power spectra revealed more structural information at low masses, where series of homologous peaks could be observed, compared with the spectra at high power.
Edwin L Kugler - One of the best experts on this subject based on the ideXlab platform.
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hydrocarbon class analysis of Coal Derived Liquids using high performance liquid chromatography
Fuel Processing Technology, 1996Co-Authors: David M Padlo, Ramesh B Subramanian, Edwin L KuglerAbstract:Abstract A normal-phase HPLC analysis method has been developed to separate Coal-Derived Liquids into six compound classes: aliphatics, 1-ring aromatics, 2-ring aromatics, 3-ring aromatics, 4-ring aromatics and polars. Three columns were used for the separation. A UV photo-diode-array detector was used for compound-class identification and an evaporative-light-scattering detector was used for quantitative analysis of compounds with boiling points > 600°F (315°C). Quantification methods with the evaporative-light-scattering detector are discussed in detail. A power-law model was found to mathematically describe the relationship between sample concentration and detector signal. Constants were determined for optimized detector conditions with pentane and methylene chloride mobile phases. Agreement between GC-simulated-distillation results and total mass detected in compound-class separations are excellent.