Abstract
The principles of neutron activation analysis based on purely instrumental techniques, including both conventional and cyclic activation, are outlined. The sources of errors in sampling, sample preparation, irradiation, methods for data analysis are described. Descriptions of the operation and use of a scanning Electron Microscope (SEM), a transmission Electron Microscope (TEM), an Electron probe microanalyser (EPMA) are given. The different modes of electron microanalysis and the principles of semi-quantitative elemental analysis using these modes are explained. As sample preparation has a large effect on the accuracy of any analytical technique for trace element work, methods for the preparation of hair samples and soft tissue samples employed in instrumental neutron activation analysis and in electron probe microanalysis are given. Realistic values of detection limits for liver, muscle, hair and nail samples are found for different irradiation and counting conditions in both techniques. The variation of flux in the reactor core affects the intensity of the activity produced in the sample, so method and results of measurement of these variations were investigated and are presented. Hair and nail samples collected from a selected population group in Africa were analysed using the above described techniques, as were hair samples collected from breast cancer patients and both sets of results are given. The distribution of some elements along selected lines on the hair cross section were studied using the electron probe microanalyser, whereas the elemental content of microvolumes in both pigmented and matrix areas in the hair cross section were looked at using the transmission electron microscope with electron probe microanalyser. Cancerous and non-cancerous breast tissues were analysed for their elemental content. Correlation and regression coefficients for elements in cancerous, non-cancerous breast tissue and hair samples from the same patient have been calculated. Abnormal breast tissues were examined for differences in morphological appearance using the scanning electron microscope. Furthermore the calcified areas of abnormal breast tissues were studied by the transmission electron microscope. The structure and composition of these calcifications, when examined, using electron diffraction and X-ray microanalysis, were found to be needle shaped crystals of hydroxyapatite.