Continuous flow analysis of iron in zinc electrowinning electrolyte using an iron chalcogenide glass ion-selective electrode: Part I. Synthetic media

It is shown that the iron(III) chalcogenide glass membrane ion-selective electrode (ISE) can be calibrated in continuous flow analysis (CFA) using acidified iron(III) nitrate standards, yielding a 60±3 mV per decade change in activity of Fe3+ response in the range 10−7–10−2 M total iron(III). Extended ageing of the iron(III) ISE in 2 M zinc(II) sulphate did not alter the potentiometric response characteristics of the electrode. Furthermore, electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy in the presence and absence of zinc(II) sulphate failed to detect a zinc(II) interference on the iron(III) ISE. CFA/ISE determined activities of Fe3+ in synthetic zinc electrolyte containing 2×10−3–2×10−1 M total iron(III) yielded results falling within ±0.2 log aFe3+ unit of the corresponding iron speciation data calculated using the minteqa2 program.