Use of ion-selective electrodes in industrial flow analysis

Two cells with ion-selective electrodes are described for industrial flow analysis, involving the flow-injection technique and continuous monitoring. The dependence of the electrode signal on the experimental parameters is discussed using the determination of cyanide as a model. It is shown that sensitive and reproducible measurements are possible even if the industrial application requires that the measuring cell be large, provided that the flow rate of the carrier liquid is sufficiently high. Large cel volumes are advantageous in continuous monitoring, as the signal approaches that obtained under steady-state conditions. Experiments with a calcium ion-selective electrode and with an ammonia gas probe show that the slow response of the sensor severely limits its applicability in flow analysis.