Scanning ion microprobe assessment of biological sample preparation techniques.

Different preparation techniques for high lateral resolution scanning ion microprobe imaging of biological samples have been investigated. The sharpest histological maps are obtained from chemically fixed and plastic embedded specimens. It is often problematic to correlate ultrastructure and bioaccumulation from analysis of frozen cut and lyophilized sections. The best compromise is to resin-embed frozen samples in order to get a perfectly flat section from tissue where the in vivo ion distribution is maintained. Use of the University of Chicago Ion Microprobe gave us the ability to observe the relative ion translocations induced during sample preparation. As an example, we show the rapid decrease of intracellular K+/Na+ ratio through a fast frozen blood droplet.