Isotopic Abundance

Isotopic Abundance

 

the relative number of atoms of the different isotopes of one chemical element. It is usually expressed as a percentage of the total of all the long-lived (having a half-life T > 3 × 108 years) isotopes of a given element, on the average, either in nature or in some reference state, such as another planet or region. A precise measurement of the isotopic abundance is of great importance in determining the atomic masses of elements.

References in periodicals archive ?
Benchmarks for stable isotopes have been established by the International Union of Pure and Applied Chemistry, or IUPAC, and its Commission on Isotopic Abundance and Atomic Weights, or CIAAW.
(2005), [C.sub.3] cycle plants, such as mango trees, which are not being submitted to stress conditions, discriminate more intensely [sup.13]C and therefore present variations in the average isotopic abundance of [sup.13]C of -27 %o, on average.
(17,63,64) Here, [delta] denotes isotopic abundance and is defined by [delta] [equivalent to] [10.sup.3] [[R.sub.sample]/[R.sub.standard] -1], where R = [sup.15]N/[sup.14]N and the standard is atmospheric [N.sub.2] (AIR).
Eight reprocessed semicoaxial germanium detectors, inherited from the previous HdM and IGEX experiments, were deployed on November 9, 2011, together with three detectors with natural isotopic abundance. In July 2012, two of the semicoaxial diodes with natural isotopic abundance were replaced by five enriched BEGe detectors.
Applying the appropriate correction factor for isotopic abundance would yield an accurate testosterone concentration for the sample (103.1 nmol/L).
Observations of the "isotopic anomaly" of positron ([sup.22]Na) annihilation lifetime spectra in samples of gaseous neon of various isotopic abundance, the independent observations of the orthopositronium lifetime anomaly, and comparison of unique experimental data on the positron's annihilation lifetime spectra in condensed deuterium ([D.sub.2]) and protium ([H.sub.2]), suggest a hypothesis on synthesis of [sup.4]He during the orthopositronium formation in deuterium.
The first approach uses variations in isotopic abundance of the stable end products arising from radioactive decay.
Keeling CD (1958) The concentration and isotopic abundance of atmospheric carbon dioxide in rural areas.
(5) This is accomplished by measuring accurately the isotopic ratio of 12C/13C, and when coupled with natural 14C isotopic abundance, this technique may be a powerful indicator of authenticity.
where [V.sub.spike] is the volume of the added spike solution (mL), [C.sub.spike] solution iS the concentration of the element in the spike solution (atoms/mL), M is the molar mass (g/mol) of the element, [N.sub.A] is Avogadro's constant, [m.sub.sample] is the mass of the soil sample (g), h is the relative abundance of the lighter ([sup.111]Cd) or heavier ([114.sup]Cd) isotope in the spike solution (taken from Table 1), or the natural isotopic abundance in the sample.
"As an industrial civilization, we're driving changes in the isotopic abundances because we're burning carbon," Frank says.