Special Features of Activation Analysis

Due to the high sensitivity, activation analysis is one of the most important methods for determination of microcomponents, in particular trace elements, in materials of high purity (e.g. in semiconductors), in water, in biological samples and in minerals. The main fields of apphcation are  

Another special feature of activation analysis is the fact that, in contrast to other methods, impurities introduced after irradiation in the course of chemical operations by reagents do not affect the results, because these impurities are not activated. 

Activation analysis is a blank-free technique. In general, blanks not oiJy determine the limits of detection, but at low concentrations they cause the main problems with respect to accuracy, because the small amounts to be determined have to be conveyed through all the steps of the chemical procedures, from sampHng to detection, without introducing systematic errors. These problems are not encountered in activation analysis, because contamination by other radionucHdes can, in general, be excluded and losses of the radionuclides to be determined can easily be detected by activity measurements. 

For these reasons, activation analysis is preferably applied for certification and calibration purposes in trace element analysis. On the other hand, activation analysis is seldom used as a routine method, because handling of radioactive samples and disposal of the radioctive waste require special precautions. 

An important aim of activation analysis is high activation of the trace elements to be determined and low activation of the main components. In this respect, the ratios of the cross sections of the elements to be determined (af) and of the main components (Z(Tm) and the half-lives are important. The higher the ratio 7x/S(7m, the more favourable is the application of activation analysis. Furthermore, if the half-lives of the activation products of the main components are shorter than those of the radionuclides to be measured, the activity of the latter is determined some appropriate time after the end of irradiation. If they are relatively long, the time of irradiation is chosen in such a way that activation of the elements to be determined is high, whereas activation of the main components is low. 

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