Chromoionophore-Mediated Imaging of Water Transport in Ion-Selective Membranes
The K+ complex of 2-(4-dipropylaminophenylazo)benzoic acid octadecyl ester (ETH 2418), a new lipophilic chromoionophore, is used to monitor the water uptake of dry solvent polymeric membranes based on 2-nitrophenyl octyl ether/poly(vinyl chloride) (2:1). Upon contact with an alkaline solution, its λmax changes from 535 to 435 nm. This process can be reversed by drying the membranes. From the time-dependent recordings of absorbance changes, an apparent water diffusion coefficient, DH2O*, of 2×10-8 cm2 s-1 is determined. In contrast to results obtained with hydrophilic water indicators, no light scattering due to water droplets is observed in the bulk of the membrane.
Zwickl, T., Schneider, B., Lindner, E., Sokalski, T., Schaller, U., & Pretsch, E. (1998). Chromoionophore-Mediated Imaging of Water Transport in Ion-Selective Membranes. Analytical Sciences, 14 (1), 57-61. https://doi.org/10.2116/analsci.14.57