Biological X‐Ray Microanalysis

Abstract

By means of X-ray microanalysis it is now practical to detect approximately 10⁻¹⁹ g of an element in a static-probe analysis within an ultrathin section, with analytical spatial resolution in the range 20–30 nm. The main difficulties for biological microanalysis are connected not with sensitivity but with specimen preparation and beam damage. Careful cryopreparation, beginning with the quench-freezing of a small block of tissue, is essential even for determining the storage sites, or sites of binding in vivo, of physiologically active elements. In frozen-dried or frozen-hydrated sections of quench-frozen tissue, it is now possible to measure local mass fractions of diffusible as well as of bound elements.