Secondary ion mass microanalysis: applications in biology.

"Secondary ion emission analysis", a method of surface microanalysis proposed in 1960 by Castaing and Slodzian, has been applied to the study of biological tissues by several groups in Europe and United States. Compared to X-ray or electron energy loss analysis, the main advantage of this method as applied in biological research is its very high sensitivity which makes it possible to easily obtain images distribution of many nuclides in a tissue section even when the concentration of these nuclides is very low (0.1 ppm or less). On the other hand, the spatial resolution is not better than 0.5 micron and observation of the specimen at the ultrastructural level is not yet possible. Another disadvantage of this method is the difficulty to obtain quantitative data. Thus, in the present state of the art, the typical field of research where the biologist can take advantage of Secondary Ion Mass Microanalysis (SIMM) is the qualitative chemical and isotopic analysis of elements at a low concentration in a cellular volume of the order of 1 micron 3.