The Experts below are selected from a list of 312 Experts worldwide ranked by ideXlab platform
Alan G Marshall - One of the best experts on this subject based on the ideXlab platform.
-
Tetramethylammonium hydroxide as a reagent for Complex Mixture analysis by negative ion electrospray ionization mass spectrometry.
Analytical chemistry, 2013Co-Authors: Vladislav V. Lobodin, Amy M Mckenna, Ryan P Rodgers, Priyanka Juyal, Alan G MarshallAbstract:Ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS) enables the direct characterization of Complex Mixtures without prior fractionation. High mass resolution can distinguish peaks separated by as little as 1.1 mDa), and high mass accuracy enables assignment of elemental compositions in Mixtures that contain tens of thousands of individual components (crude oil). Negative electrospray ionization (ESI) is particularly useful for the speciation of the most acidic petroleum components that are implicated in oil production and processing problems. Here, we replace conventional ammonium hydroxide by tetramethylammonium hydroxide (TMAH, a much stronger base, with higher solubility in toluene) to more uniformly deprotonate acidic components of Complex Mixtures by negative ESI FTICR MS. The detailed compositional analysis of four crude oils (light to heavy, from different geographical locations) reveals that TMAH reagent accesses 1.5-6 times as many elemental compositions, spanning a much wider range of chemical classes than does NH4OH. For example, TMAH reagent produces abundant negative electrosprayed ions from less acidic and neutral species that are in low abundance or absent with NH4OH reagent. More importantly, the increased compositional coverage of TMAH-modified solvent systems maintains, or even surpasses, the compositional information for the most acidic species. The method is not limited to petroleum-derived materials and could be applied to the analysis of dissolved organic matter, coal, lipids, and other naturally occurring compositionally Complex organic Mixtures.
-
tetramethylammonium hydroxide as a reagent for Complex Mixture analysis by negative ion electrospray ionization mass spectrometry
Analytical Chemistry, 2013Co-Authors: Vladislav V. Lobodin, Amy M Mckenna, Ryan P Rodgers, Priyanka Juyal, Alan G MarshallAbstract:Ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS) enables the direct characterization of Complex Mixtures without prior fractionation. High mass resolution...
-
electrically compensated fourier transform ion cyclotron resonance cell for Complex Mixture mass analysis
Analytical Chemistry, 2011Co-Authors: Nathan K Kaiser, J Savory, Amy M Mckenna, John P Quinn, Christopher L Hendrickson, Alan G MarshallAbstract:Complex natural organic Mixtures such as petroleum require ultrahigh mass spectral resolution to separate and identify thousands of elemental compositions. Here, we incorporate a custom-built, voltage-compensated ICR cell for Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS), based on a prior design by Tolmachev to produce optimal mass resolution. The compensated ICR cell installed in a custom-built 9.4 T FTICR mass spectrometer consists of seven cylindrical segments with axial proportions designed to generate a dc trapping potential that approaches an ideal three-dimensional axial quadrupolar potential. However, the empirically optimized compensation voltages do not correspond to the most quadrupolar trapping field. The compensation electrodes minimize variation in the reduced cyclotron frequency by balancing imperfections in the magnetic and electric field. The optimized voltages applied to compensation electrodes preserve ion cloud coherence for longer transient duration by approxi...
-
atmospheric pressure photoionization fourier transform ion cyclotron resonance mass spectrometry for Complex Mixture analysis
Analytical Chemistry, 2006Co-Authors: Jeremiah M Purcell, Christopher L Hendrickson, Ryan P Rodgers, Alan G MarshallAbstract:We have coupled atmospheric pressure photoionization (APPI) to a home-built 9.4-T Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer. Analysis of naphtho[2,3-a]pyrene and crude oil mass spectra reveals that protonated molecules, deprotonated molecules, and radical molecular ions are formed simultaneously in the ion source, thereby complicating the spectra (>12 000 peaks per mass spectrum and up to 63 peaks of the same nominal mass), and eliminating the "nitrogen rule" for nominal mass determination of number of nitrogens. Nevertheless, the ultrahigh mass resolving power and mass accuracy of FT-ICR MS enable definitive elemental composition assignments, even for doublets as closely spaced as 1.1 mDa (SH3(13)C vs (12)C4). APPI efficiently ionizes nonpolar compounds that are unobservable by electrospray and allows nonpolar sulfur speciation of petrochemical Mixtures.
James G. Quinn - One of the best experts on this subject based on the ideXlab platform.
-
unresolved Complex Mixture ucm a brief history of the term and moving beyond it
Marine Pollution Bulletin, 2015Co-Authors: John W Farrington, James G. QuinnAbstract:Abstract The term “Unresolved Complex Mixture” (UCM) has been used extensively for decades to describe a gas chromatographic characteristic indicative of the presence of fossil fuel hydrocarbons (mainly petroleum hydrocarbons) in hydrocarbons isolated from aquatic samples. We chronicle the origin of the term. While it is still a useful characteristic for screening samples, more modern higher resolution two dimensional gas chromatography and gas chromatography coupled with advanced mass spectrometry techniques (Time-of-Flight or Fourier Transform-Ion Cyclotron Resonance) should be employed for analyses of petroleum contaminated samples. This will facilitate advances in understanding of the origins, fates and effects of petroleum compounds in aquatic environments.
-
unresolved Complex Mixture ucm in coastal environments is derived from fossil sources
Environmental Science & Technology, 2013Co-Authors: Helen K White, Paul C Hartmann, James G. Quinn, Li Xu, Christopher M. ReddyAbstract:The unresolved Complex Mixture (UCM) frequently dominates organic extracts isolated from estuarine and coastal sediments in the vicinity of industrial centers. Despite an obvious link to a petroleu...
Amy M Mckenna - One of the best experts on this subject based on the ideXlab platform.
-
tetramethylammonium hydroxide as a reagent for Complex Mixture analysis by negative ion electrospray ionization mass spectrometry
Analytical Chemistry, 2013Co-Authors: Vladislav V. Lobodin, Amy M Mckenna, Ryan P Rodgers, Priyanka Juyal, Alan G MarshallAbstract:Ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS) enables the direct characterization of Complex Mixtures without prior fractionation. High mass resolution...
-
Tetramethylammonium hydroxide as a reagent for Complex Mixture analysis by negative ion electrospray ionization mass spectrometry.
Analytical chemistry, 2013Co-Authors: Vladislav V. Lobodin, Amy M Mckenna, Ryan P Rodgers, Priyanka Juyal, Alan G MarshallAbstract:Ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS) enables the direct characterization of Complex Mixtures without prior fractionation. High mass resolution can distinguish peaks separated by as little as 1.1 mDa), and high mass accuracy enables assignment of elemental compositions in Mixtures that contain tens of thousands of individual components (crude oil). Negative electrospray ionization (ESI) is particularly useful for the speciation of the most acidic petroleum components that are implicated in oil production and processing problems. Here, we replace conventional ammonium hydroxide by tetramethylammonium hydroxide (TMAH, a much stronger base, with higher solubility in toluene) to more uniformly deprotonate acidic components of Complex Mixtures by negative ESI FTICR MS. The detailed compositional analysis of four crude oils (light to heavy, from different geographical locations) reveals that TMAH reagent accesses 1.5-6 times as many elemental compositions, spanning a much wider range of chemical classes than does NH4OH. For example, TMAH reagent produces abundant negative electrosprayed ions from less acidic and neutral species that are in low abundance or absent with NH4OH reagent. More importantly, the increased compositional coverage of TMAH-modified solvent systems maintains, or even surpasses, the compositional information for the most acidic species. The method is not limited to petroleum-derived materials and could be applied to the analysis of dissolved organic matter, coal, lipids, and other naturally occurring compositionally Complex organic Mixtures.
-
electrically compensated fourier transform ion cyclotron resonance cell for Complex Mixture mass analysis
Analytical Chemistry, 2011Co-Authors: Nathan K Kaiser, J Savory, Amy M Mckenna, John P Quinn, Christopher L Hendrickson, Alan G MarshallAbstract:Complex natural organic Mixtures such as petroleum require ultrahigh mass spectral resolution to separate and identify thousands of elemental compositions. Here, we incorporate a custom-built, voltage-compensated ICR cell for Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS), based on a prior design by Tolmachev to produce optimal mass resolution. The compensated ICR cell installed in a custom-built 9.4 T FTICR mass spectrometer consists of seven cylindrical segments with axial proportions designed to generate a dc trapping potential that approaches an ideal three-dimensional axial quadrupolar potential. However, the empirically optimized compensation voltages do not correspond to the most quadrupolar trapping field. The compensation electrodes minimize variation in the reduced cyclotron frequency by balancing imperfections in the magnetic and electric field. The optimized voltages applied to compensation electrodes preserve ion cloud coherence for longer transient duration by approxi...
Ryan P Rodgers - One of the best experts on this subject based on the ideXlab platform.
-
tetramethylammonium hydroxide as a reagent for Complex Mixture analysis by negative ion electrospray ionization mass spectrometry
Analytical Chemistry, 2013Co-Authors: Vladislav V. Lobodin, Amy M Mckenna, Ryan P Rodgers, Priyanka Juyal, Alan G MarshallAbstract:Ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS) enables the direct characterization of Complex Mixtures without prior fractionation. High mass resolution...
-
Tetramethylammonium hydroxide as a reagent for Complex Mixture analysis by negative ion electrospray ionization mass spectrometry.
Analytical chemistry, 2013Co-Authors: Vladislav V. Lobodin, Amy M Mckenna, Ryan P Rodgers, Priyanka Juyal, Alan G MarshallAbstract:Ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS) enables the direct characterization of Complex Mixtures without prior fractionation. High mass resolution can distinguish peaks separated by as little as 1.1 mDa), and high mass accuracy enables assignment of elemental compositions in Mixtures that contain tens of thousands of individual components (crude oil). Negative electrospray ionization (ESI) is particularly useful for the speciation of the most acidic petroleum components that are implicated in oil production and processing problems. Here, we replace conventional ammonium hydroxide by tetramethylammonium hydroxide (TMAH, a much stronger base, with higher solubility in toluene) to more uniformly deprotonate acidic components of Complex Mixtures by negative ESI FTICR MS. The detailed compositional analysis of four crude oils (light to heavy, from different geographical locations) reveals that TMAH reagent accesses 1.5-6 times as many elemental compositions, spanning a much wider range of chemical classes than does NH4OH. For example, TMAH reagent produces abundant negative electrosprayed ions from less acidic and neutral species that are in low abundance or absent with NH4OH reagent. More importantly, the increased compositional coverage of TMAH-modified solvent systems maintains, or even surpasses, the compositional information for the most acidic species. The method is not limited to petroleum-derived materials and could be applied to the analysis of dissolved organic matter, coal, lipids, and other naturally occurring compositionally Complex organic Mixtures.
-
atmospheric pressure photoionization fourier transform ion cyclotron resonance mass spectrometry for Complex Mixture analysis
Analytical Chemistry, 2006Co-Authors: Jeremiah M Purcell, Christopher L Hendrickson, Ryan P Rodgers, Alan G MarshallAbstract:We have coupled atmospheric pressure photoionization (APPI) to a home-built 9.4-T Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer. Analysis of naphtho[2,3-a]pyrene and crude oil mass spectra reveals that protonated molecules, deprotonated molecules, and radical molecular ions are formed simultaneously in the ion source, thereby complicating the spectra (>12 000 peaks per mass spectrum and up to 63 peaks of the same nominal mass), and eliminating the "nitrogen rule" for nominal mass determination of number of nitrogens. Nevertheless, the ultrahigh mass resolving power and mass accuracy of FT-ICR MS enable definitive elemental composition assignments, even for doublets as closely spaced as 1.1 mDa (SH3(13)C vs (12)C4). APPI efficiently ionizes nonpolar compounds that are unobservable by electrospray and allows nonpolar sulfur speciation of petrochemical Mixtures.
Rafael Brüschweiler - One of the best experts on this subject based on the ideXlab platform.
-
Web server suite for Complex Mixture analysis by covariance NMR.
Magnetic Resonance in Chemistry, 2009Co-Authors: Fengli Zhang, Steven L. Robinette, Lei Bruschweiler-li, Rafael BrüschweilerAbstract:Elucidation of the chemical composition of biological samples is a main focus of systems biology and metabolomics. Their comprehensive study requires reliable, efficient, and automatable methods to identify and quantify the underlying metabolites. Because nuclear magnetic resonance (NMR) spectroscopy is a rich source of molecular information, it has a unique potential for this task. Here we present a suite of public web servers (http://spinportal.magnet.fsu.edu), termed COLMAR, which facilitates Complex Mixture analysis by NMR. The COLMAR web portal presently consists of three servers: COLMAR covariance calculates the covariance NMR spectrum from an NMR input dataset, such as a TOCSY spectrum; COLMAR DemixC method decomposes the 2D covariance TOCSY spectrum into a reduced set of nonredundant 1D cross sections or traces, which belong to individual Mixture components; and COLMAR query screens the traces against a NMR spectral database to identify individual compounds. Examples are presented that illustrate the utility of this web server suite for Complex Mixture analysis.
-
web server based Complex Mixture analysis by nmr
Analytical Chemistry, 2008Co-Authors: Steven L. Robinette, Fengli Zhang, Lei Bruschweilerli, Rafael BrüschweilerAbstract:Comprehensive metabolite identification and quantification of Complex biological Mixtures are central aspects of metabolomics. NMR shows excellent promise for these tasks. An automated fingerprinting strategy is presented, termed COLMAR query, which screens NMR chemical shift lists or raw 1D NMR cross sections taken from covariance total correlation spectroscopy (TOCSY) spectra or other multidimensional NMR spectra against an NMR spectral database. Cross peaks are selected using local clustering to avoid ambiguities between chemical shifts and scalar J-coupling effects. With the use of three different algorithms, the corresponding chemical shift list is then screened against chemical shift lists extracted from 1D spectra of a NMR database. The resulting query scores produced by forward assignment, reverse assignment, and bipartite weighted-matching algorithms are combined into a consensus score, which provides a robust means for identifying the correct compound. The approach is demonstrated for a metaboli...
-
non negative matrix factorization of two dimensional nmr spectra application to Complex Mixture analysis
Journal of Chemical Physics, 2008Co-Authors: David A Snyder, Fengli Zhang, Steven L. Robinette, Lei Bruschweilerli, Rafael BrüschweilerAbstract:A central problem in the emerging field of metabolomics is how to identify the compounds comprising a chemical Mixture of biological origin. NMR spectroscopy can greatly assist in this identification process, by means of multi-dimensional correlation spectroscopy, particularly total correlation spectroscopy (TOCSY). This Communication demonstrates how non-negative matrix factorization (NMF) provides an efficient means of data reduction and clustering of TOCSY spectra for the identification of unique traces representing the NMR spectra of individual compounds. The method is applied to a metabolic Mixture whose compounds could be unambiguously identified by peak matching of NMF components against the BMRB metabolomics database.