Isotopic fractionation study design

Studies of oxygen isotope fractionation were undertaken to address the mechanisms of the oxidative and reductive phases of SOD catalysis.44 Experiments were conducted at pH 10 in either borate or carbonate buffer where the rate is only slightly diminished from that at physiological pH. Control experiments demonstrated that all of the 02 produced came from the enzymatic reaction rather than the spontaneous disproportionation that occurs in the presence of trace metal ions slowly as the pH is increased. The reaction proceeds rapidly to 100% completion giving equal concentrations of 02 and H202 therefore, a ratio of fractionation factors was determined from the distribution of the lsO isotope in the two products. The ratio of fractionation factors reflects the ratio of KIEs on the oxidative and reductive reactions, and is designated as (3 (Equation 9.9). The (3 was determined to be 1.0104 0.0012 under the conditions described above. 

A series of papers by Merz and Riedel describe work designed to compare radiochemical behaviour following n,y n,p E.C. and p decay. Gallium isotopes are produced in most of the cases studied, but isotopes of Sn, Pb, Ge and Sb were also involved. Unfortunately, the various chromatography fractions were not well identified, so that it is not easy to draw definite conclusions from this work. Nevertheless, several things do appear to be clear. Some interesting data are presented in Table 5, comparing the effects of electron capture, neutron capture, and the (n,p) reaction. 

Isotopic investigations are widely used in soil/plant nutritional and pollution studies. Introduction of an isotope by design or accident enables specific fractions or pools to be labeled, making it possible to follow rates of exchange between soil matrices soil solution-plant uptake and drainage water. The usefulness of this technique ultimately depends upon the availability of an isotope, with a suitable half-life. A number of recent pollution incidents have involved both stable (lead petroleum additions) and radioisotopes (including and 1). 

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