scholarly journals Intestinal β-carotene bioconversion in humans is determined by a new single-sample, plasma isotope ratio method and compared with traditional and modified area-under-the-curve methods

2018 ◽  
Vol 653 ◽  
pp. 121-126 ◽  
Author(s):  
Jennifer Lynn Ford ◽  
Michael H. Green ◽  
Joanne Balmer Green ◽  
Anthony Oxley ◽  
Georg Lietz
Keyword(s):  
Isotope Ratio ◽  
Area Under The Curve ◽  
Single Sample ◽  
Ratio Method ◽  
Β Carotene

scholarly journals Graphite Isotope Ratio Method Development Report: Irradiation Test Demonstration of Uranium as a Low Fluence Indicator

10.2172/13875 ◽  
1999 ◽  
Author(s):  
B.D. Reid ◽  
D.C. Gerlach ◽  
E.F. Love ◽  
J.P. McNeece ◽  
J.V. Livingston ◽  
...  
Keyword(s):  
Isotope Ratio ◽  
Method Development ◽  
Ratio Method ◽  
Irradiation Test

scholarly journals Vitamin A Absorption Determined in Rats Using a Plasma Isotope Ratio Method

2020 ◽  
Vol 150 (7) ◽  
pp. 1977-1981 ◽  
Author(s):  
Michael H Green ◽  
Joanne Balmer Green
Keyword(s):  
Vitamin A ◽  
Oral Dose ◽  
Isotope Ratio ◽  
Cholesterol Absorption ◽  
Absorption Efficiency ◽  
Intravenous Dose ◽  
Ratio Method ◽  
Sprague Dawley ◽  
Retinyl Acetate ◽  
Dose Fraction

ABSTRACT Background Better methods are needed for determining vitamin A absorption efficiency. Objective Our objective was to measure vitamin A absorption in rats by adapting a plasma isotope ratio method previously used to determine cholesterol absorption. Methods Male Sprague-Dawley rats [n = 14; 340 ± 16 g (mean ± SD)] received an oral tracer dose of [3H]retinyl acetate in oil plus an intravenous dose of [14C]vitamin A–labeled lymph prepared in a donor rat that had received [14C]retinyl acetate intraduodenally. Blood samples were collected on days 1, 2, 3, 6, 9, and 12, and plasma was analyzed for 3H and 14C; vitamin A absorption was calculated for each sample as (fraction of oral dose/fraction of intravenous dose) × 100. Radioactivity was also measured in feces and urine collected as pools on days 3, 6, 9, and 12 and in liver and remaining carcass on day 12. Results Vitamin A absorption calculated as the plasma isotope ratio was >100% on day 1, 78% ± 5% on day 6, 76% ± 5% on day 9, and 74% ± 5% on day 12; fitting the data to an exponential function plus a constant predicted an absorption of 75% by day 14. Recovery of the oral dose in feces (day 0 to day 6) was low (6.2% ± 0.84%, n = 10) and the mean isotope ratio in day 9–12 urine pool was lower than that in plasma. Conclusions The plasma isotope ratio holds promise for estimating vitamin A absorption, but additional work is needed to determine how long studies need to be and if the doses should be administered simultaneously. For application of this method in humans, artificial chylomicrons labeled with a stable isotope of retinyl acetate could be used for the intravenous dose, with a different isotope required for the oral dose.

scholarly journals Isotopic compositions of the elements 2009 (IUPAC Technical Report)

2011 ◽  
Vol 83 (2) ◽  
pp. 397-410 ◽  
Author(s):  
Michael Berglund ◽  
Michael E. Wieser
Keyword(s):  
Mass Spectrometry ◽  
Isotope Ratio ◽  
Critical Evaluation ◽  
Isotope Ratio Mass Spectrometry ◽  
Atomic Weight ◽  
Single Sample ◽  
International Union ◽  
Isotopic Compositions ◽  
Technical Report ◽  
Isotopic Abundances

The Commission on Isotopic Abundances and Atomic Weights (CIAAW) of the International Union of Pure and Applied Chemistry (IUPAC) completed its last update of the isotopic compositions of the elements as determined by isotope-ratio mass spectrometry in 2009. That update involved a critical evaluation of the published literature and forms the basis of the table of the isotopic compositions of the elements (TICE) presented here. For each element, TICE includes evaluated data from the “best measurement” of the isotope abundances in a single sample, along with a set of representative isotope abundances and uncertainties that accommodate known variations in normal terrestrial materials. The representative isotope abundances and uncertainties generally are consistent with the standard atomic weight of the element Ar(E) and its uncertainty U[Ar(E)] recommended by CIAAW in 2007.

scholarly journals Simultaneous measurement of <i>δ</i><sup>13</sup>C, <i>δ</i><sup>18</sup>O and <i>δ</i><sup>17</sup>O of atmospheric CO<sub>2</sub> – performance assessment of a dual-laser absorption spectrometer

2021 ◽  
Vol 14 (6) ◽  
pp. 4279-4304
Author(s):  
Pharahilda M. Steur ◽  
Hubertus A. Scheeren ◽  
Dave D. Nelson ◽  
J. Barry McManus ◽  
Harro A. J. Meijer
Keyword(s):  
Quality Control ◽  
Isotope Ratio ◽  
Measurement Precision ◽  
Ratio Method ◽  
Laser Absorption ◽  
Calibration Methods ◽  
Precision And Accuracy ◽  
Control Tank ◽  
Dual Laser ◽  
Absorption Spectrometer

Abstract. Using laser absorption spectrometry for the measurement of stable isotopes of atmospheric CO2 instead of the traditional isotope ratio mass spectrometry method decreases sample preparation time significantly, and uncertainties in the measurement accuracy due to CO2 extraction and isobaric interferences are avoided. In this study we present the measurement performance of a new dual-laser instrument developed for the simultaneous measurement of the δ13C, δ18O and δ17O of atmospheric CO2 in discrete air samples, referred to as the Stable Isotopes of CO2 Absorption Spectrometer (SICAS). We compare two different calibration methods: the ratio method, based on the measured isotope ratio and a CO2 mole fraction dependency correction, and the isotopologue method, based on measured isotopologue abundances. Calibration with the ratio method and isotopologue method is based on three different assigned whole-air references calibrated on the VPDB (Vienna Pee Dee Belemnite) and the WMO 2007 (World Meteorological Organization) scale for their stable isotope compositions and their CO2 mole fractions, respectively. An additional quality control tank is included in both methods to follow long-term instrument performance. Measurements of the quality control tank show that the measurement precision and accuracy of both calibration methods is of similar quality for δ13C and δ18O measurements. During one specific measurement period the precision and accuracy of the quality control tank reach WMO compatibility requirements, being 0.01 ‰ for δ13C and 0.05 ‰ for δ18O. Uncertainty contributions of the scale uncertainties of the reference gases add another 0.03 ‰ and 0.05 ‰ to the combined uncertainty of the sample measurements. Hence, reaching WMO compatibility for sample measurements on the SICAS requires reduction of the scale uncertainty of the reference gases used for calibration. An intercomparison of flask samples over a wide range of CO2 mole fractions has been conducted with the Max Planck Institute for Biogeochemistry, resulting in a mean residual of 0.01 ‰ and −0.01 ‰ and a standard deviation of 0.05 ‰ and 0.07 ‰ for the δ13C measurements calibrated using the ratio method and the isotopologue method, respectively. The δ18O could not be compared due to depletion of the δ18O signal in our sample flasks because of storage times being too long. Finally, we evaluate the potential of our Δ17O measurements as a tracer for gross primary production by vegetation through photosynthesis. Here, a measurement precision of <0.01 ‰ would be a prerequisite for capturing seasonal variations in the Δ17O signal. Lowest standard errors for the δ17O and Δ17O of the ratio method and the isotopologue method are 0.02 ‰ and 0.02 ‰ and 0.01 ‰ and 0.02 ‰, respectively. The accuracy results show consequently results that are too enriched for both the δ17O and Δ17O measurements for both methods. This is probably due to the fact that two of our reference gases were not measured directly but were determined indirectly. The ratio method shows residuals ranging from 0.06 ‰ to 0.08 ‰ and from 0.06 ‰ to 0.1 ‰ for the δ17O and Δ17O results, respectively. The isotopologue method shows residuals ranging from 0.04 ‰ to 0.1 ‰ and from 0.05 ‰ to 0.13 ‰ for the δ17O and Δ17O results, respectively. Direct determination of the δ17O of all reference gases would improve the accuracy of the δ17O and thereby of the Δ17O measurements.

Stable Carbon Isotope Ratio Method For Detection Of Corn-Derived Acetic Acid In Apple Cider Vinegar: Collaborative Study

1992 ◽  
Vol 75 (4) ◽  
pp. 725-728 ◽  
Author(s):  
Dana A Krueger
Keyword(s):  
Acetic Acid ◽  
Carbon Isotope ◽  
Isotope Ratio ◽  
Collaborative Study ◽  
Stable Carbon Isotope ◽  
Carbon Isotope Ratio ◽  
Ratio Method ◽  
Published Data ◽  
Stable Carbon ◽  
Stable Carbon Isotope Ratio

Abstract The stable carbon isotope ratio analysis method for determining the presence of corn-derived acetic acid in cider vinegar has been collaboratively studied. The method is based upon natural differences in the 13C /12C ratio; pure cider vinegars yield δ13C results near -25 %o, while corn vinegar yields results near -10 %o. Samples are combusted at 500 C in sealed glass tubes over CuO. The purified CO2 is analyzed by isotope ratio mass spectrometry relative to the Pee Dee belemnite limestone (PDB) standard. The precision of this method was observed to be similar to that of other isotope ratio methods that have been collaboratively studied: SR ranged from 0.6 to 1.2, while sr ranged from 0.1 to 1.1. The results indicate that as little as 10% added corn vinegar may be detected in cider vinegar. On the basis of published data of the natural variability of cider vinegar 13C /12C ratios, it is recommended that samples yielding results more positive than -22.0 %o be classified as not pure cider vinegar using this method. This method has been adopted first action by AOAC International.

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