Summary

X-ray microanalysis has developed into a reliable technique for the determination of the intracellular distribution of elements, due to the use of cryopreparation techniques that preserve the in vivo localisation of diffusible elements, and the introduction of quantitative techniques. X-ray microanalysis is now used for investigating a great number of biological problems. The major fields of application are environmental biology/toxicology and physiology/pathology. In human and animal physiology (and pathology), studies have concentrated on the role of calcium in cellular processes; but ion transport in epithelia, under both normal and pathological conditions, is also an important field of study. Furthermore, the possible relation of Na+ ions to mitogenesis and oncogenesis is a problem where X-ray microanalysis has made interesting contributions.

Introduction

Biologists have been using electron probe X-ray microanalysis for the past 30 years to complement the morphological information provided by the electron beam with the chemical information provided by the process of X-ray generation in the specimen. The first applications were carried out using a crystal spectrometer, but when energy-dispersive (semiconductor-based) spectrometers became available, these soon became the dominating type of instrument for biological X-ray microanalysis. Energy-dispersive spectrometers were easier to handle, allowed the analysis of all elements simultaneously, and had a better efficiency, which allowed lower beam currents. Only in the analysis of microdroplets (Roinel, 1988) is the wavelength-dispersive spectrometer the instrument of choice.