Radiochemical separation techniques

For matrices other than silicon, such as GaAs, InSb, AlGaAs, and InP, it is difficult to measure trace elements because the activity from the matrix is intense and long-lived. In these cases, laborious radiochemical separation techniques are employed to measure impurities. 

Contents Introduction. - Experimental Techniques Production of Energetic Atoms. Radiochemical Separation Techniques. Special Physical Techniques. - Characteristics of Hot Atom Reactions Gas Phase Hot Atom Reactions. Liquid Phase Hot Atom Reactions. Solid Phase Hot Atom Reactions. - Applications of Hot Atom Chemistry and Related Topics Applications in Inorganic, Analytical and Geochemistry. Applications in Physical Chemistry. Applications in Biochemistry and Nuclear Medicine. Hot Atom Chemistry in Energy-Related Research. Current Topics Related to Hot Atom Chemistry and Future Scope. - Subject Index. 

To illustrate three common radiochemical separation techniques - precipitation, solvent extraction, and cation exchange - in parts 7A, 7B, and 1C. These methods separate thorium from its uranium parent. Radionuclide recovery is measured by comparing count rates to the original sample, not by carrier yield determination. 

In all of the experiments using a fast radiochemical separation technique, the form of the target has great influence on the separation speed as shown in the following examples. 

In 1981, Herrmann summarized (Herrmann 1981) the results of searches for SHEs in damped collisions of with U carried out at the UNILAC at Darmstadt utilizing their unique high-energy uranium beams to bombard uranium targets. A wide variety of radiochemical separation techniques and a rotating-wheel system were used to search for elements 108 to 118 and even 126. These experiments were also to no avail and upper limits of 10 , 10 , and 10 cm were set on the cross sections for half-Kves of 1 to 100 ms, 100 ms to 1 day, and 1 day to 1 year, respectively. However, he predicted that the planned increases in fluence levels would permit reaching cross sections below these levels. Subsequently, the search for the production of SHEs in damped collisions (see Chap. 3 in Vol. 1) with (6.2—7.3 MeV/nucleon) at the... 

UNILAC was extended to Cm targets (Kratz et al. 1986) because this reaction was predicted to have a higher cross section. Comprehensive aqueous- and gas-phase radiochemical separation techniques were used to isolate SHE fractions that were then assayed for SF activity, including fission-fragment total kinetic energies, and neutron emission. Again, the results were negative with upper cross-section limits of 10 cm for half-lives of minutes to hours and 4 X 10 cm for half-lives from days to several years. 

An interesting radiochemical separation technique.developed recently... 

Meyer, R.A. Rapid automated batchwize radiochemical separation techniques. J. Radioanal. Nucl. Chem. Art. 142, 135-144 (1990)... 

Geochemists were some of the first researchers to realize the enormous benefits of ICP-MS for the determination of trace elements in digested rock samples. Until then, they had been using a number of different techniques, including neutron activation analysis (NAA), thermal ionization mass spectrometry (TIMS), ICP-OES, x-ray techniques, and GFAA. Unfortunately, they all had certain limitations, which meant that no one technique was suitable for all types of geochemical samples. For example, NAA was very sensitive, but when combined with radiochemical separation techniques for the determination of rare earth elements, it was extranely slow and expensive to run. TIMS was the technique of choice for carrying out isotope ratio studies because it offered excellent precision, but unfortunately was painfully slow. Plasma... 

Many laboratories employ radiochemical separation techniques to isolate groups of elements from the sample after irradiation. The combination of simple group separations and high-resolution gamma-ray spectroscopy reduces substantially the analysis time and analytical costs, and makes the technique nearly a true multielement method. Additional effort is being expended to automate these group separations to further decrease analytical costs. 

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