Sample Preparations Used in Biomedical Research and Training at the Special Training Division of the Oak Ridge Institute of Nuclear Studies

A very wide variety of sample preparation is used in the Special Training Division's research and teaching programmes. These range from simple source holders such as metal, cardboard and plastic source mounts, to precipitation devices using stainless steel and fibreglass mounts, and special source holders for liquid counting of samples. In addition to these techniques, a number of procedures of special interest in biomedical problems have been developed. One of the most important of these is the use of a catalytic synthesis of benzene which has been developed to the point to which an over-all yield of better than 90% is obtained. This synthesis can be used for carbon-containing compounds of interest in low-level tracing experiments and age dating problems. Since the synthesis involves the production of carbon dioxide at one step and the hydration of metallic carbide in another, it can be used either for the measurement of 14C or 3H or both in double labelling experiments. Considerable work is done on activation analysis of biological materials, particularly in the Division's radioecological programmes. Special techniques for the preparation of these materials for activation analysis and other radiochemical procedures are described. Since the problem of resolution in alpha-ray spectroscopy remains a very difficult one, considerable work is carried out by the oceanography and environmental studies group in the development of very thin samples which are capable of permitting higher resolution of alpha-ray spectra. These employ electrodeposition procedures from mixed solvents. Measurements are made with a special bank of Fairstein-Frisch grid counters associated with a 512-channel analyser for simultaneous recording of more than one spectrum. Solid-state detectors are also used and comparative results of gridded and solid-state detectors are shown. (author)