Introduction

Quantitation routines which have been developed for use in materials science cannot usually be applied to biological specimens because biological material has special characteristics.

1. (a) It usually consists of elements of interest such as sodium, magnesium, potassium etc., which are present at low concentrations (less than 5%) in an organic matrix of the low atomic number elements carbon, hydrogen, oxygen and nitrogen. These matrix elements are not detected by the usual beryllium window detector. Because of this composition, standards are required when biological material is analysed.

2. (b) The major component of living tissue is water. This is generally removed during specimen preparation, though hydrated tissue can be studied if a suitable cold stage is available.

3. (c) Biological specimens often present a rough surface and are of uneven thickness.

Because of these factors, software for the application of quantitation to biological specimens must include routines which are able to cope with the differences in specimen thickness that are encountered (e.g. using the Hall method) and also offer routines for the estimation of local water content. In addition, the programme should be easy to use and should be capable of processing spectra automatically when large amounts of data are being collected (as is the case with biological specimens).