A near edge X-ray absorption fine structure (NEXAFS) study of the response mechanism of the iron (III) chalcogenide glass membrane ion-selective electrode

•Proof of electron transfer and ion exchange with the iron(III) ISE.•NEXAFS can detect low surface concentrations of electrochemically active species.•Presence of iron(II) and iron(III) in the MSL of the iron(III) ISE.

We have utilized synchrotron radiation-X-ray photoelectron spectroscopy (SR-XPS) and near edge X-ray absorption fine structure (NEXAFS) to demonstrate unequivocally that the modified surface layer (MSL) of the iron chalcogenide glass ion-selective electrode (ISE) comprises a mixture of iron(II) and iron(III) redox states, as proposed in previous theories to explain the mixed electron transfer and ion exchange response mechanism of this analytically important ISE.

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