X-ray microanalysis: a histochemical tool for elemental analysis

Abstract

The interactions of electrons with specimens Types of interactionsWhen electrons strike an object, as in an electron microscope, a number of interactions occur that can be, and are, used to give information about the specimen (Table 1). The various types of interactions of electrons that are used to produce images in scanning or transmission electron microscopes are familiar to most biologists, in the form of electron micrographs. The density of a transmission electron micrograph is dependent on the mass of the specimen at that point; because of this, staining and histochemical methods have been developed for electron microscopy using heavy metals. In scanning electron microscopy, the generation of back-scattered electrons is also dependent on atomic number. The information that can be obtained about the composition of the specimen in these ways is, however, extremely crude compared with that obtainable by some other methods. Among these other methods is X-ray microanalysis (also known as electron probe microanalysis) which is foremost among such techniques at present for ease of application and interpretation, and availability of commercial equipment. In X-ray microanalysis, the electrons striking the specimen excite X-rays characteristic of the elements in the specimen. X-ray microanalysis is thus a form of elemental analysis. It has been applied to a wide variety of biological problems, and these will be considered later in the section entitled Some biological applications of X-ray microanalysis. The production of X-rays by electronsWhen an electron of sufficient energy passes through the cloud of electrons surrounding an atomic nucleus, it may cause the displacement of an inner orbital electron to an orbit of higher energy. In the process the primary electron is inelastically scattered; that is, it

Calcification of intraocular hydrogel lens: evidence of dystrophic calcification

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Comparison of bromine and permanganate as ultrastructural stains for lignin in plants infected by the fungus Colletotrichum lagenarium

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