There is considerable interest in the application of X-ray microanalysis to the study of biological specimens since this is one of the few techniques which allows the study of diffusible elements at a subcellular level. Although it is easy to obtain element ratios from spectra produced by X-ray microanalysis, fully quantitative data are required for the results to take their place alongside those obtained by use of other physiological techniques. Quantitative data are still published routinely from only a small number of laboratories, implying that some difficulties may be encountered in the application of quantification to biological specimens. Here, the two main methods used for obtaining quantitative results from the analysis of thin sections will be outlined briefly; details of other methods can be found in Hall (1989a). The discussion will concentrate on the appraisal and interpretation of results as this is an area where problems may arise.

The preparative steps involved in the study of diffusible elements are, firstly, cryofixation (reviewed by Zierold, this volume), which is usually followed by cryosectioning and analysis of the sections in the frozen–dried state (the sections can be analysed frozen–hydrated, but this is technically much more difficult – see Warley & Gupta, 1991). As an alternative the cryofixed specimen may be freeze dried and embedded, or embedded using low temperature techniques. The initial part of this discussion will focus on the quantification of data obtained from the analysis of frozen–dried cryosections; in a later section the problems encountered when applying quantitation to embedded material will be highlighted.