Biological strandard for electron microprobe analysis of intracellular sodium concentration

A method is described for the determination of the intracellular concentration of sodium in individual cells using the electron microprobe analyzer. This method gives an accuracy equal to that obtained by using flame photometry on tissues with large cell populations. Intracellular sodium was precipitated in the cell by a fixative containing pyroantimonate. Cartilaginous needles from shark fins which were equilibrated in saline solutions of differing concentrations were used as biological standards.