TXRF, PIXE, SYXRF; principles, critical comparison and applications

At first glance X-Ray fluorescence analysis seems to be a very sensitive and effectful method to detect element traces in the multielement mode. But in praxi the application range is restricted, if X-Ray tubes are used as excitation sources. To overcome this situation, it is necessary to improve the conditions of excitation and to reduce the background, produced by different scattering effects. TXRF, PIXE and SYXRF, which allow multielement analysis in the trace- and ultratrace region are using this strategy. In the case of TXRF a remarkable background reduction is achieved if the sample is prepared as a thin amorphous film on a planar sample holder and the excitation beam of a X-Ray tube is totally reflected on its surface. In the case of PIXE a particle beam of high intensity is used as excitation source, improving the conditions of excitation and giving the opportunity of spatial resolved analyses. In the case of SYXRF the X-Ray fraction of synchrotron radiation is used as excitation source, giving the opportunity, to improve the conditions of excitation as well as to reduce the background by using the high polarisation of the beam. In this case, too, spatial resolved analysis are possible. The principles of the three methods are described, their advantages and disadvantages are critically compared and advanced applications from different analytical fields are presented. (orig.)