engleski

Spectropotentiometric investigations od solvent polymer sensor membranes

Various time-dependent processes in the bulk of solvent polymer membranes based on plasticized poly(vinly chloride) are analyzed with a flow-through cell mounted on a microscope equipped with optical filters.A CCD camer is used to record pictures with a resolution of ca. 2 ?m. Water uptake of dry membranes is monitored through a new lipophilic water indicator. From time.dependent absorbance changes, an apparent water diffusion coefficient., D*H2O of 2x10-8 cm2 s-1 is determined. In contrast to earlier results obtained with hidrophilic water indicators, we found that D*H2O is not time-dependent and no light scattering owing to water droplets occurs in the bulk of the membrane. Recently, it has been shown that cation interference induces long-term potential drifts of H+- selective electrode membranes based on a lipopohilic chromoionophore. These drifts have been correlated with diffusion processes by simultaneously monitoring the concentration profiles od the protonated and unprotonated chromoionophore.

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