Surface studies of crystal membrane ion-selective electrodes

Abstract EN

The surfaces of fluoride, silver-sulfide, and cupric ion-selective electrode membranes have been studied by X-ray photoelectron spectroscopy (XPS) scanning electron microscopy (SEM) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFT).

It is shown that the fluoride electrode membrane possesses a hydrated gel layer -20 nm thick.

This layer allows the relatively free migration of the fluoride ion; however, it also provides a pathway by which the hydroxide ion can interfere with the fluoride exchange process^Studies show that aging of the lanthanum fluoride membrane occurs within this Mrated gel layer with the formation of hydrolyzed lanthanum species.

These hydrolyzed species are believed to be responsible for slowing of the electrode response with time.

The surface of the silver-sulfide electrode membrane undergoes photoox- idation in aqueous solution, and this reaction determines the response mechanism of the membrane.

Chemical oxidation of the surface of the cupnc electrode membrane plays an important role in the response mechanism of the electrode.