Radiochemical complications

The difficulties include the inconvenience of handling radioactivity and the necessity for obtaining an accurate radiochemical analysis of two phases containing several elements (which often involves complicated spectra). Highly sensitive instrumentation is required for the analysis e.g. a Li-Si surface barrier detector for a particles, a 2 r gas counter for (3-radiation and a Li-Ge detector for 7-radiation. Great care is required during source preparation, which is best done by electrodeposition. 

The study of the oral bioavailability of enzymes is very complicated. When using radiochemical methods, the amounts of absorbed enzymes are overestimated,... 

Radiochemical tracers or radiotracers are compounds labeled with radioisotopes. For tracer methods, the compound to be measured or a suitable reagent is radiolabeled. A measurement of the redistribution of tracer within such a sample-reagent reaction system provides the required quantitative analytical information. Major advantages of tracer methods are high sensitivity, simplicity, and speed. Radiotracers are more commonly used for following mechanisms of biological and/or chemical processes or if there is need to eliminate complicated separation procedures, especially in biological processes. 

The final area to be discussed here involves the study of thermal ion reactions by recoil methods. This represents one of the newest applications reported and potentially one of the most exciting. Studies to date are unique in that they incorporate a combination of radiochemical detection that allows investigation of submicroscopic ion concentrations and recoil energetics that often ensures escape from solvation. Thus, isolated ions can be studied in the liquid phase without the complications of ion pairing or solvation, and truly thermal processes involving gas phase ions that are diflBcult at best to observe in chemical accelerators due to space change limits can be investigated. 

In addition, Staehelln and Holgne (23-25). from Information In the radiochemical literature, have provided a clear (although In practice, complicated) picture of the radical cycle in the so-called "Indirect" ozonation reactions, whereby superoxide is also formed from the reaction of hydroxyl radical with organic compounds in the presence of oxygen. 

On the basis of experience using the ceramic melters and present developments in this field, the present feasibility of Russian Pu-containing materials is assessed. Rich Pu wastes from the radiochemical and chemical-metallurgical production of plutonium are included in this category of wastes for example, hard-to-dissolve residues after treatment by a mixture of nitric and fluoride acids. These wastes have a complicated chemical composition (Table 3). 

The cis isomer of PA is most suitable as a material for a positive electrode. But it changes to the trans form with time and becomes brittle. Radiochemical irradiation of cis-PA results in the formation of rare knots between polymer chains and complicates the isomerization to the trans form [157]. It also results in the stabilization of PA, which retains electrochemical activity for a long time, whereas without such a treatment PA quickly loses electrochemical activity. 

Gamma spectra can be quite complex, as a result of both complicated emission spectra and detector artefacts. Radiochemical data are from The Radiochemical Manual unless indicated otherwise. There is the possibility of peak overlaps as a result of finite detector resolution, two of which are significant to the present discussion ... 

Recent applications of photon activation to the analysis of heavy elements include the determination of Te, Sr, and Pb. Campbell and Steele measured Te in the presence of U by Ge(Li) spectrometry of the activated Te isotope [ Te(y,n) Te] with a half-life of 17 d. The method is useful because it avoids the complications arising in n.a.a. caused by fission of the uranium giving rise to direct and spectral interferences from fission products. The measurement of "Sr induced by Sr(), n) and Sr(y,y ) reactions using 30 MeV Bremsstrahlung has been applied to the analysis of Sr in sea-water at the 8 p.p.m. level this involved a radiochemical separation of the 2—8 h Sr. The (y,n) reaction of Pb has been used for the determination of Pb in milk powder.Measurement of the Pb isotope (/ 52 h) after a non-specific sulphate precipitation of the Pb is sufficient to attain a limit of detection of 0.5 //g. The activity was measured with a NaI(TI) detector after "Sr, which was also produced, had decayed. 

---