Light microscopy has been used for the evaluation of the internal and external structure of dry microcapsules. The method involves surface and penetrative staining with various dyes after which the microcapsules were embedded in suitable optically translucent material. Using this method the core material, its shape and position within the microcapsules either in total or as subunits of the core are clearly distinguishable from the wall material. The surface characteristics of the microcapsules can be observed with either light or fluorescent microscopy after staining with a fluorescent dye. Furthermore, it is a relatively simple and inexpensive method by comparison with the scanning electron microscopy. The natural character of microcapsules, without any artificial structures, has been maintained. It could serve as a routine auxiliary method for complex evaluation or control of the microencapsulation process and its optimization.

Faculty of Pharmacy Charles University Department of Pharmaceutical Technology Hradec Králové Czechoslovakia

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