Stable isotope Relative atomic mass Mole fraction 106 Cd 105.906 460 0.012 45 108 Cd 107.904 183 0.008 88 110 Cd 109.903 007 0.124 70 111 Cd 110.904 183 0.127 95 112 Cd 111.902 763 0.241 09 113 Cd 112.904 408 0.122 27 114 Cd 113.903 365 0.287 54 116 Cd 115.904 763 0.075 12 Radioactive isotope having a relatively long half-life and a characteristic terrestrial isotopic composition that contributes significantly and reproducibly to the determination of the standard atomic weight of the element in normal materials. Half-lives of 113 Cd and 116 Cd are 8.04 10 15 years and 2.9 10 19 years, respectively.
Cadmium isotopes in biology Heavy-metal accumulation is a threat to our world s water systems and wildlife. As a way measure the influence heavy metals on wildlife, some researchers use animal food enriched in specific cadmium isotopes. These experiments work by exposing the animals to a diet enriched in 106 Cd and/or other stable isotopes of metals (for example, 65 Cu and/or 62 Ni) for a period of time. Depending on the purpose of the experiment, the residence time of the food in the gut is determined and isotopic compositions of the gut and/or feces are measured via inductively coupled plasma mass spectrometry (ICP-MS). This information is used to measure bio-uptake (absorption and incorporation of a substance by living tissue) and accumulation rates of metals in an exposed animal [356-358]. Cadmium isotopes in Earth/planetary science Molecules, atoms, and ions of the stable isotopes of cadmium possess slightly different physical, chemical, and biological properties, and they commonly will be isotopically fractionated during physical, chemical, and biological processes, giving rise to variations in isotopic abundances and in atomic weights. There are small but measureable variations in the isotopic abundances of dissolved cadmium in ocean water, which are a consequence of isotopic fractionation associated with biological uptake (Figure 1) [356-360]. Fig. 1: Cadmium isotopic composition of dissolved ocean cadmium as a function of latitude for the Zero Meridian surface water samples (modified from Xue et al. [360], with data from Abouchami et al. [359]). Cadmium isotopes used as a source of radioactive isotope(s)
112 Cd is used to produce the diagnostic radioisotope 111 In via the reaction 112 Cd (p, 2n) 111 In [361, 362].
Glossary analyte chemical substances or materials undergoing analysis. atomic number (Z) The number of protons in the nucleus of an atom. atomic weight (relative mean atomic mass) the sum of the products of the relative atomic mass and the mole fraction of each stable and long-lived radioactive isotope of that element in the sample. The symbol of the atomic weight of element E is A r (E), and the symbol of the atomic weight of an atom (isotope) of element E having mass number A is A r ( A E). Because relative atomic masses are scaled (expressed relative) to one-twelfth the mass of a carbon-12 atom, atomic weights are dimensionless. [return] electron elementary particle of matter with a negative electric charge and a rest mass of about 9.109 10 31 kg. element (chemical element) a species of atoms; all atoms with the same number of protons in the atomic nucleus. A pure chemical substance composed of atoms with the same number of protons in the atomic nucleus [703]. [return] gamma rays (gamma radiation) a stream of high-energy electromagnetic radiation given off by an atomic nucleus undergoing radioactive decay. The energies of gamma rays are higher than those of X-rays; thus, gamma rays have greater penetrating power. half-life (radioactive) the time interval that it takes for the total number of atoms of any radioactive isotope to decay and leave only one-half of the original number of atoms. [return] inductively coupled plasma mass spectroscopy (ICPMS) a type of mass spectrometry in which the analyte is inductively heated and analyzed in a plasma created with an electromagnetic coil, yielding mass fractions as low as approximately 1 part per 10 15. [return] isotope one of two or more species of atoms of a given element (having the same number of protons in the nucleus) with different atomic masses (different number of neutrons in the nucleus). The atom can either be a stable isotope or a radioactive isotope. isotopic abundance (mole fraction or amount fraction) the amount (symbol n) of a given isotope (atom) in a sample divided by the total amount of all stable and long-lived radioactive isotopes of the chemical element in the sample. [return] isotopic composition number and abundance of the isotopes of a chemical element that are naturally occurring [706]. [return] isotopic fractionation (stable-isotope fractionation) preferential enrichment of one isotope of an element over another, owing to slight variations in their physical, chemical, or biological properties [706]. [return]
neutron an elementary particle with no net charge and a rest mass of about 1.675 10 27 kg, slightly more than that of the proton. All atoms contain neutrons in their nucleus except for protium ( 1 H). normal material a reasonably possible source for an element or its compounds in commerce, for industry or science; the material is not itself studied for some extraordinary anomaly and its mole fractions (isotopic abundances) have not been modified significantly in a geologically brief period [4]. [return] proton an elementary particle having a rest mass of about 1.673 10 27 kg, slightly less than that of a neutron, and a positive electric charge equal and opposite to that of the electron. The number of protons in the nucleus of an atom is the atomic number. radioactive decay the process by which unstable (or radioactive) isotopes lose energy by emitting alpha particles (helium nuclei), beta particles (positive or negative electrons), gamma radiation, neutrons or protons to reach a final stable energy state. radioisotope (radioactive isotope) an atom for which radioactive decay has been experimentally measured (also see half-life). [return] residence time the average amount of time that a particle spends in a specified system. [return] stable isotope an atom for which no radioactive decay has ever been experimentally measured. [return] standard atomic weight an evaluated quantity assigned by the IUPAC Commission on Isotopic Abundances and Atomic Weights (CIAAW) to encompass the range of possible atomic weights of a chemical element that might be encountered in all samples of normal terrestrial materials. It is comprised of either an interval (currently for 12 elements) or a value and an uncertainty (a standard Atomic-weight uncertainty), and currently there are 72. A standard atomic weight is determined from an evaluation of peer-reviewed scientific publications. [return] X-rays electromagnetic radiation with a wavelength ranging from 0.01 to 10 nanometers shorter than those of UV rays and typically longer than those of gamma rays.
References 4. C. Kendall, and Coplen, T.B. Hydrological Process. 15, 1363 (2011). 10.1002/hyp.217 356. M. N. Croteau, Luoma, S.N., and Pellet, B. Aquatic Toxicology. 83, 116 (2007). 357. M. N. Croteau, and Luoma, S.N. Environmental Science & Technology. 43, 4915 (2009). 358. F. Lacan, Francois, R., Ji, Y., and Sherrell, R.M. Geochimica et Cosmochimica Acta. 70 (20), 5104 (2006). 359. S. J. G. G. W. Abouchami, H. J. W. de Baar, A. C. Alderkamp, R. Middag, P. Laan, H. Feldmann, and M. O. Andreae. Earth Planetary Science Letters. 305, 83 (2011). 360. M. R. Z. Xue, T. J. Horner, W. Abouchami, R. Middag, T. van de Flierd, and H. J. W. de Baar. Earth and Planetary Science Letters. 382, 161 (2013). 361. T. S. I. Inc. Cadmium Isotopes. Trace Sciences International Inc. 2014 Feb. 26. http://www.tracesciences.com/cd.htm 362. I. A. E. Agency. International Atomic Energy Agency, Vienna (2009). 703. I. U. o. P. a. A. Chemistry. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Blackwell Scientific Publications, Oxford (1997). 706. Coplen. Rapid Communications in Mass Spectrometry. 25 (2011).