%0 Generic %1 Pomerantz:2009p4011 %A Pomerantz, Andrew E %A Hammond, Matthew R %A Morrow, Amy L %A Mullins, Oliver C %A Zare, Richard N %D 2009 %J Energy & Fuels %K Analysis, Aromatic-Hydrocarbons, Asphaltenes, Chromatography, Correlation Crude-Oil, Desorption, Distributions, Fluorescence Ionization, Multiphoton Petroleum Polycyclic Size-Exclusion Spectral Spectroscopy Uv-Fluorescence, Weight %P 1162--1168 %R 10.1021/ef8006239 %T Asphaltene Molecular-Mass Distribution Determined by Two-Step Laser Mass Spectrometry %U http://pubs.acs.org/doi/abs/10.1021/ef8006239 %V 23 %X Two-step laser mass spectrometry ((LMS)-M-2) is explored as a technique to measure the molecular-mass distribution of asphaltenes. Unlike widely used laser desorption/ionization (LDI) mass spectrometry, in which a single laser pulse is used to desorb and ionize asphaltenes, (LMS)-M-2 involves two laser pulses and spatially and temporally separates the desorption and ionization events. This process allows (LMS)-M-2 to measure the asphaltene molecular-mass distribution free from artifacts resulting from aggregation and insufficient laser power, as occur in LDI. Studies of relevant model compounds show that (LMS)-M-2 detects these molecules without aggregation (unlike LDI), with only a minimum of fragmentation/multiple charging, and with relatively uniform sensitivity across the relevant mass range; however, the efficiency of the resonant ionization process is sensitive to molecular structure. These data suggest that (LMS)-M-2 does not suffer from significant mass discrimination in the relevant mass range and that (LMS)-M-2 provides a slight underestimate of the asphaltene molecular-mass distribution. Petroleum asphaltenes from different geographical origins are found to have similar mass spectra, all showing a peak at every nominal mass under an envelope beginning at 200 units, peaking at 500-600 units, and extending to 1000-1500 units. Coal asphaltenes are found to be considerably lighter and less complex, showing pronounced clusters of peaks separated by 14 units under an envelope beginning at 200 units, peaking at 300 units, and extending to 500 units. These results bring the molecular-mass distribution of asphaltenes as measured by laser desorption mass spectrometry in accordance with many other mass spectrometry and diffusion measurements.

@proceedingspaper{Pomerantz:2009p4011, abstract = {Two-step laser mass spectrometry ((LMS)-M-2) is explored as a technique to measure the molecular-mass distribution of asphaltenes. Unlike widely used laser desorption/ionization (LDI) mass spectrometry, in which a single laser pulse is used to desorb and ionize asphaltenes, (LMS)-M-2 involves two laser pulses and spatially and temporally separates the desorption and ionization events. This process allows (LMS)-M-2 to measure the asphaltene molecular-mass distribution free from artifacts resulting from aggregation and insufficient laser power, as occur in LDI. Studies of relevant model compounds show that (LMS)-M-2 detects these molecules without aggregation (unlike LDI), with only a minimum of fragmentation/multiple charging, and with relatively uniform sensitivity across the relevant mass range; however, the efficiency of the resonant ionization process is sensitive to molecular structure. These data suggest that (LMS)-M-2 does not suffer from significant mass discrimination in the relevant mass range and that (LMS)-M-2 provides a slight underestimate of the asphaltene molecular-mass distribution. Petroleum asphaltenes from different geographical origins are found to have similar mass spectra, all showing a peak at every nominal mass under an envelope beginning at 200 units, peaking at 500-600 units, and extending to 1000-1500 units. Coal asphaltenes are found to be considerably lighter and less complex, showing pronounced clusters of peaks separated by 14 units under an envelope beginning at 200 units, peaking at 300 units, and extending to 500 units. These results bring the molecular-mass distribution of asphaltenes as measured by laser desorption mass spectrometry in accordance with many other mass spectrometry and diffusion measurements.}, added-at = {2010-06-22T19:38:37.000+0200}, affiliation = {Schlumberger Doll Res Ctr, Cambridge, MA 02139 USA}, author = {Pomerantz, Andrew E and Hammond, Matthew R and Morrow, Amy L and Mullins, Oliver C and Zare, Richard N}, biburl = {https://www.bibsonomy.org/bibtex/27c53dfb63cab81047f994198e8b7297b/gsmith}, date-added = {2010-05-24 13:52:36 -0400}, date-modified = {2010-05-24 13:52:48 -0400}, doi = {10.1021/ef8006239}, interhash = {21d2848b5f2177f158a83ea300610bad}, intrahash = {7c53dfb63cab81047f994198e8b7297b}, journal = {Energy {\&} Fuels}, keywords = {Analysis, Aromatic-Hydrocarbons, Asphaltenes, Chromatography, Correlation Crude-Oil, Desorption, Distributions, Fluorescence Ionization, Multiphoton Petroleum Polycyclic Size-Exclusion Spectral Spectroscopy Uv-Fluorescence, Weight}, language = {English}, local-url = {file://localhost/Users/geoffreysmith/Documents/Papers/Energy%20&%20Fuels/2009/Energy%20&%20Fuels,%2023,%201162-1168%202009.pdf}, month = Jan, pages = {1162--1168}, pmid = {000265439000005}, rating = {0}, timestamp = {2010-06-22T19:39:20.000+0200}, title = {Asphaltene Molecular-Mass Distribution Determined by Two-Step Laser Mass Spectrometry}, uri = {papers://E88B624E-D406-46FF-9D95-BB9C1AAE3FDC/Paper/p4011}, url = {http://pubs.acs.org/doi/abs/10.1021/ef8006239}, volume = 23, year = 2009 }