The Experts below are selected from a list of 249 Experts worldwide ranked by ideXlab platform

Maret G Traber - One of the best experts on this subject based on the ideXlab platform.

  • studies in humans using deuterium labeled α and γ tocopherols demonstrate faster plasma γ tocopherol disappearance and greater γ metabolite production
    Free Radical Biology and Medicine, 2005
    Co-Authors: Scott W. Leonard, Rajasekhar Ramakrishnan, Elaine Paterson, Carroll E Cross, Jeffrey Atkinson, Maret G Traber
    Abstract:

    Abstract We hypothesized that human plasma α- and γ-tocopherol concentrations reflect differences in their kinetics, especially influenced by γ-tocopherol metabolism. Vitamin E kinetics were evaluated in humans ( n = 14) using ∼50 mg each of an equimolar ratio of d 6 -α- and d 2 -γ-tocopheryl acetates administered orally. Mass spectrometry was used to measure deuterated plasma tocopherols, as well as plasma and urinary vitamin E metabolites, α- and γ-carboxyethylhydroxychromans (CEHCs). Plasma d 2 -γ-tocopherol fractional disappearance rates (FDR; 1.39 ± 0.44 pools/day, mean ± SD) were more than three times greater than those of d 6 -α-tocopherol (0.33 ± 0.11, p d 2 -γ-tocopherol half-life was 13 ± 4 h compared with 57 ± 19 for d 6 -α-tocopherol. Whereas neither plasma nor urinary d 6 -α-CEHC was Detectable (Limit of detection 1 nmol/L), γ-CEHC (labeled plus unlabeled) increased from 129 ± 20 to 258 ± 40 nmol/L by 12 h and returned to baseline by 48 h; at 12 h d 2 -γ-CEHC represented 54 ± 4% of plasma γ-CEHC. Women compared with men had a greater d 2 -γ-tocopherol FDR ( p d 2 -γ-CEHC concentration ( p p d 2 -γ-CEHC ( p

J.-s. Chung - One of the best experts on this subject based on the ideXlab platform.

  • Comparison of a mosaic-crystal spectrometer to a high-performance solid-state detector for x-ray microfluorescence analysis
    1998
    Co-Authors: J.-s. Chung, S. Isa, C. J. Sparks, G. E. Ice, S. Mchugo, A.c. Thompson
    Abstract:

    The minimum-Detectable-Limit of a compact double-focusing graphite mosaic-crystal spectrometer is compared to the minimum-Detectable-Limit from a high-performance Ge solid-state detector. The solid angle and efficiency of the solid-state detector is much greater than for the crystal spectrometer. However, the better signal-to-noise of the spectrometer and its insensitivity to matrix fluorescence and scattering can give it a better minimum-Detectable-Limit for trace element analysis. The relative advantages of the two detectors are illustrated for some simple test samples. The performance of the crystal spectrometer compared to the solid-state detector increases as the flux in the x-ray probe increases. This makes crystal spectrometers especially interesting for use with new high intensity 3rd generation synchrotron microprobes. An estimate is made of the source and sample conditions favored for each detector

  • Comparison Of A Mosaic-Crystal Spectrometer To Ahigh-Performance Solid-State Detector For X-Ray Microfluorescence Analysis
    MRS Proceedings, 1998
    Co-Authors: J.-s. Chung, S. Isa, C. J. Sparks, G. E. Ice, S. Mchugo, A. Thompson
    Abstract:

    ABSTRACTThe minimum-Detectable-Limit of a compact double-focusing graphite mosaic-crystal spectrometer is compared to the minimum-Detectable-Limit from a high-performance Ge solidstate detector. The solid angle and efficiency of the solid-state detector is much greater than for the crystal spectrometer. However, the better signal-to-noise of the spectrometer and its insensitivity to matrix fluorescence and scattering can give it a better minimum-Detectable-Limit for trace element analysis. The relative advantages of the two detectors are illustrated for some simple test samples. The performance of the crystal spectrometer compared to the solid-state detector increases as the flux in the x-ray probe increases. This makes crystal spectrometers especially interesting for use with new high intensity 3rd generation synchrotron microprobes. An estimate is made of the source and sample conditions favored for each detector.

James N. Seiber - One of the best experts on this subject based on the ideXlab platform.

  • Simplified method for trace analysis of trifluoroacetic acid in plant, soil, and water samples using headspace gas chromatography
    Analytical Chemistry, 1999
    Co-Authors: Thomas M. Cahill, Jody A. Benesch, Mae Sexauer Gustin, Erica J. Zimmerman, James N. Seiber
    Abstract:

    A simple and sensitive analytical procedure was developed to determine the concentration of trifluoroacetic acid (TFA) in plant, soil, and water samples. The analysis involves extraction of TFA by sulfuric acid and methanol followed by derivatization to the methyl ester of TFA (MTFA). This is accomplished within a single vial without complex extraction procedures. The highly volatile MTFA is then analyzed using headspace gas chromatography. The spike recovery trials from all media ranged from a low of 86.7% to a high of 121.4%. The relative standard deviations (RSDs) were typically below 10%, although some tests had higher RSDs due to low concentrations near the Detectable Limit. The minimum Detectable Limit (MDL) for the method was 34 ng/g for dry plant material, 0.20 ng/g for soil, and 6.5 ng/L for water. This is the first practical method for low-level analysis of TFA in plants and soil, and it is a significant improvement over previous methods for TFA in water.

A.c. Thompson - One of the best experts on this subject based on the ideXlab platform.

  • Comparison of a mosaic-crystal spectrometer to a high-performance solid-state detector for x-ray microfluorescence analysis
    1998
    Co-Authors: J.-s. Chung, S. Isa, C. J. Sparks, G. E. Ice, S. Mchugo, A.c. Thompson
    Abstract:

    The minimum-Detectable-Limit of a compact double-focusing graphite mosaic-crystal spectrometer is compared to the minimum-Detectable-Limit from a high-performance Ge solid-state detector. The solid angle and efficiency of the solid-state detector is much greater than for the crystal spectrometer. However, the better signal-to-noise of the spectrometer and its insensitivity to matrix fluorescence and scattering can give it a better minimum-Detectable-Limit for trace element analysis. The relative advantages of the two detectors are illustrated for some simple test samples. The performance of the crystal spectrometer compared to the solid-state detector increases as the flux in the x-ray probe increases. This makes crystal spectrometers especially interesting for use with new high intensity 3rd generation synchrotron microprobes. An estimate is made of the source and sample conditions favored for each detector

A. Thompson - One of the best experts on this subject based on the ideXlab platform.

  • Comparison Of A Mosaic-Crystal Spectrometer To Ahigh-Performance Solid-State Detector For X-Ray Microfluorescence Analysis
    MRS Proceedings, 1998
    Co-Authors: J.-s. Chung, S. Isa, C. J. Sparks, G. E. Ice, S. Mchugo, A. Thompson
    Abstract:

    ABSTRACTThe minimum-Detectable-Limit of a compact double-focusing graphite mosaic-crystal spectrometer is compared to the minimum-Detectable-Limit from a high-performance Ge solidstate detector. The solid angle and efficiency of the solid-state detector is much greater than for the crystal spectrometer. However, the better signal-to-noise of the spectrometer and its insensitivity to matrix fluorescence and scattering can give it a better minimum-Detectable-Limit for trace element analysis. The relative advantages of the two detectors are illustrated for some simple test samples. The performance of the crystal spectrometer compared to the solid-state detector increases as the flux in the x-ray probe increases. This makes crystal spectrometers especially interesting for use with new high intensity 3rd generation synchrotron microprobes. An estimate is made of the source and sample conditions favored for each detector.