A novel spectroscopic method to image H2O distribution in ion-selective membranes

Chromoionophore-Mediated Imaging of Water Transport in Ion-Selective Membranes

“…According to preliminary gravimetric measurements, it lies in the order of 100 so that D H 2 O is estimated as ca. 10 -6 cm 2 s -1 , in good accordance with the values measured by Harrison et al 12 In contrast to the results obtained earlier with hydrophilic indicators 7,8 , we observed no light scattering due to heterogeneous water and no initial fast stage of water uptake. It is likely that both these differences are related to each other.…”

“…Absorbance values near the edges of the ring are biased by diffraction, unevenness and/or light scattering by water droplets (at the inner membrane rim). 7,9,10 In addition, the membrane shrinks to a certain extent the longer it is exposed to the alkaline solution. Both effects make an interpretation in the border region impossible.…”

“…The time-and distance-resolved distribution of water in liquid polymer membranes was first monitored by Harrison and coworkers 7 who applied a spatial imaging photometry technique with CoCl 2 and the solvatochromic dye, 2,6-diphenyl-4-(2,4,6-triphenyl-Npyridino)phenolate, as water indicators. Time-dependent apparent water diffusion coefficients, D * H2O , for dry membranes were determined with this technique.…”

“…[1][2][3] Consequently, they always contain a certain amount of water, a fact recognized already in the seventies [4][5][6] and studied intensively by the group of Harrison in the nineties. [7][8][9][10][11][12][13] It is well known that clear plasticized PVC membranes may become cloudy when soaked in water and transparent again when the process is reversed through drying. The uptake of water may affect the performance of polymer membranes in ionselective electrodes (ISEs) and optodes in several ways.…”

Multispectral imaging of ion transport in neutral carrier‐based cation‐selective membranes

“…The stacked membrane approach in conjunction with pH-sensitive chromoionophores has been used later for the optical determination of the distribution of free and complexed ionophore across the membrane (18). The first high-resolution true imaging technique for studying transport processes in ISE membranes was described by Harrison and coworkers (19,20). The authors used CoCl 2 as a water sensitive dye in combination with a spatial imaging photometer to study the water uptake of potassium selective PVC membranes.…”