Unsegmented flow analysis with ion-selective electrodes by use of a large-volume wall-jet cell Continuous electrode reactivation in the determination of fluoride and chloride

A simple, large-volume wall-jet cell was designed for unsegmented flow analysis. The working electrode is immersed in a solution that reactivates the electrode surface. During the sample measurement, the working electrode is screened from the reactivation solution by the streaming sample solution; between the individual samples, air is pumped through the jet and agitates the reactivating solution at the electrode surface. The properties of the cell were investigated with the fluoride and chloride ion-selective electrodes and the method was applied to determination of fluoride and chloride in steel corrosion products and in a reference sample of the fly dust from electric-arc furnaces. The method permits about 90 measurements per hour, the results are reproducible and the limits of determination (6.3 x 10(-8) and 2.3 x 10(-7)M for fluoride and chloride, respectively) are substantially lower than the values commonly obtained in batch experiments. At least 150 measurements can be carried out without significant changes in the reliability of determination and the reactivation solution can then be replaced.