Electron microprobe calibration for measurement of intracellular water.

A set of six albumin standards has been prepared to contain tissue solids fractions ranging from approximately 10 to 38% solids. Samples of each different standard were quick frozen in cooled propane, freeze-dried at low temperature and embedded in EPON 826 containing dibromoacetophenone. Electron microprobe measurement of reduction of Br L alpha signal was plotted against tissue water fraction to provide a calibration for tissue water measurement in biological soft tissue. The relationship between electron microprobe measurement of Br L alpha and tissue water fraction was linear with correlation coefficient .991. Using the calibration established with this work, uncertainty of measurement of tissue water fraction in a tissue sample that is 80% water will be approximately 5%.