AJP - Cell Physiology, Vol 262, Issue 5 C1324-C1334, Copyright © 1992 by American Physiological Society
Calibration of ion-selective microelectrodes
T. L. Croxton and W. M. Armstrong
Department of Physiology and Biophysics, Indiana University School of Medicine, Indianapolis 46202-5120.
Measurements of intracellular and extracellular ion activities with
ion-selective microelectrodes generally involve calibration of the
electrodes in solutions of known composition and fitting of the calibration
data with a theoretical expression. The Nicolsky equation is frequently
used to describe the variation of electrode potential with primary ion
activity in the presence of a constant amount of interference. In this
report, we review the estimation of primary ion activities in calibration
solutions and discuss the practical use of the Nicolsky equation. We
describe a specialized computer program, developed in this laboratory, for
routine input and editing of calibration data, fitting of data with the
Nicolsky equation, and calculation of experimental ion activities from the
fitted curve. Earlier versions of this program have proven helpful in
several investigations in this and in other laboratories.
