Principles of X-ray microanalysis in biology.

Progress in biological X-ray microanalysis has been limited in recent years by specimen preparation procedures. Instrumentation and high levels of sensitivity for low concentrations are well developed for a large number of biological applications but reliable preparation of samples in the thick or thin form has yet to be establisehd. In addition the possible damage of specimens by the electron probe has been incompletely studied in the majority of applications. In this review the basic principles of X-ray production, design and operation of X-ray detectors, quantitative procedures for thick and thin samples, analytical operation of the microscope, and current specimen preparation techniques are briefly described with the aim of highlighting weaknesses and discussing recent developments in each field.