Introduction to X-ray microanalysis in biology

This paper gives an introduction to X-ray microanalysis for biologists. The physical principles of X-ray microanalysis and the instrumentation used in wavelength-dispersive and energy-dispersive analysis are reviewed. A special problem in biological microanalysis is the adequate preparation of the specimen: The preparative method must retain the localization of the element(s) of interest and allow identification of morphological features at the level of analytical resolution. Conventional preparation methods for electron microscopy have only a limited applicability in biological X-ray microanalysis, and often cryomethods have to be used. Methods for qualitative analysis and some common pitfalls and artefacts are discussed. The possibilities and limitations of electron-probe X-ray microanalysis with regard to biological specimens are compared to those of other microanalytical techniques.