Flow injection analysis. Part VII. Use of ion-selective electrodes for rapid analysis of soil extracts and blood serum. Determination of potassium, sodium and nitrate

Abstract

The flow injection principle is used with novel design of a flow cell, in which the ion-selective and reference electrode are incorporated. The reproducible mixing of the sample with the carrier stream of electrolyte and the precise timing of potentiometric measurements in the continuously moving stream are the most important parameters influencing the quality of direct potentiometric measurements. Methods for the determination of nitrate and potassium in soil extracts, and sodium and potassium in blood sera are described. At sampling rates of 125 determinations per hour, a standard deviation of only 0.8 % is typical. Simultaneous measurements of two ions on one stream are described; advantages and drawbacks of the use of ion-selective electrodes in continuous flow measurements are discussed; and the new possibilities which the flow injection method offers are contemplated. © 1977.