Scanning Microscopy


T. A. Hall


This review summarizes existing formalisms for the quantitative analysis of biological specimens, and considers the analysis of bulk specimens, micro-droplets, homogenates, and thin or ultrathin sections, respectively. For (ultra)thin sections, one may use elemental ratios for semi-quantitative analysis, measure elemental concentrations as mmol/volume using peripheral standards, or as mmol/kg using the continuum method. Often it is physiologically more relevant to know the concentration of ions as mmol/kg water. This can be achieved by analysing the specimen first in the frozen-hydrated state and then again after freeze-drying, or by using a peripheral standard. Attention has to be given to the selection of a proper preparative method to ensure biologically relevant quantitative results. Quantitative analysis of sections of freeze-dried, embedded tissue will, due to tissue shrinkage during freeze-drying and incomplete penetration of resin, result in data that are intermediate between "wet weight" concentrations and "dry weight" concentrations. Analysis under cold-stage conditions may generally be expected to reduce mass loss during analysis.

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