Flow-through units for solid-state, liquid and PVC matrix membrane ion-selective electrodes to minimise streaming potentials

ANALYSTANALYST Pub Date: DOI: 10.1039/AN9871201293

Abstract

When making measurements with ion-selective electrodes in continuous flow systems, potential oscillations are observed which are due to changes in the flow-rate and consequently to changes in streaming potentials. Three different flow-through units suitable for potentiometric measurements with solid-state, liquid and PVC matrix membrane electrodes have been constructed. In all the units, streaming potential oscillations were reduced to ?0.2 mV by minimising the distance between the sensing membrane and the external reference electrolyte-sample solution contact zone. Air-segmented streams were used to evaluate the units at flow-rates of 1.74, 3.64 and 6.70 ml min–1. Sampling rates as high as 60, 120 and 240 h–1, respectively, were achieved.

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