A microelectrometric titration method for measurement of total intracellular Cl- concentration

A microelectrometric titration method is described to measure picomole amounts of Cl- present in solutions at micromolar concentrations. This method was used to measure total intracellular chloride concentration ([Cl-]i) in leukocytes. Through the use of submicroliter samples, [Cl-] can be measured in the range of 5-500 microM. There is no measurable interference from other ions normally present in the cell and no intracellular ion is falsely measured as Cl-. [Cl-]i determined by the conventional coulometric titration and the new microelectrometric titration method was the same. Among the commonly used substituting anions, thiocyanate was the only one falsely measured as Cl- and should be avoided in experiments using this method. Because only picomole amounts of Cl- are required, measurements of intracellular pH and total concentrations of other intracellular ions can be done in the same lysate of as few as 5 X 10(5) cells. This feature should make it possible to study the time course of changes in [Cl-]i together with measurements of other intracellular ions following various physiological or experimental maneuvers.