FTIR-ATR Study of Water Uptake and Diffusion through Ion-Selective Membranes Based on Poly(acrylates) and Silicone Rubber

Abstract

For the first time, FTIR-ATR spectroscopy was used to study the water uptake and its diffusion in ion-selective membranes (ISMs) based on poly(acrylates) (PAs) and silicone rubber (SR), which are emerging materials for the fabrication of ISMs for ultratrace analysis. Three different types of PA membranes were studied, consisting of copolymers of methyl methacrylate with n-butyl acrylate, decyl methacrylate, or isodecyl acrylate. Numerical simulations with the finite difference method showed that in most cases the water uptake of the PA and SR membranes could be described with a model consisting of two diffusion coefficients. The diffusion coefficients of the PA membranes were approximately 1 order of magnitude lower than those of plasticized poly(vinyl chloride) (PVC)-based ISMs and only slightly influenced by the membrane matrix composition. However, the simulations indicated that during longer contact times, the water uptake of PA membranes was considerably higher than that for plasticized PVC membranes. Although the diffusion coefficients of the SR and plasticized PVC membranes were similar, the SR membranes had the lowest water uptake of all membranes. This can be beneficial in preventing the formation of detrimental water layers in all-solid-state ion-selective electrodes. With FTIR-ATR, one can monitor the accumulation of different forms of water, i.e., monomeric, dimeric, clustered, and bulk water.

Characterization of Salophen Co(III) Acetate Ionophore for Nitrite Recognition

“…Among the techniques used here, ATR gives us information about the "in-situ" processes that occur in the membrane phase. In other reports, ATR-IR was primarily used for monitoring water penetration into the liquids membranes, but rarely for monitoring reaction processes within membranes [14][15][16][17][18][19]. Other techniques such UV-Vis cyclic voltammetry and potentiometry were used for validating the proper functioning of the proposed sensor.…”

Pre-Polarized Hydrophobic Conducting Polymer Solid-Contact Ion-Selective Electrodes with Improved Potential Reproducibility

“…[18][19][20][21] The role of the SC is to provide a stable inner phase boundary potential 20,22,23 at the substrate/SC and SC/ISM interfaces, and to prevent the aqueous layer formation at the inner interface, which coupled to diffusion of ionic species within the ISM may lead to potential instability. 24 As all ISMs exhibit water uptake [25][26][27][28][29][30][31] , the prevention of the aqueous layer formation 32,33 with ill-defined ion activity has proven to be a major challenge.…”

Tetra(p‐tolyl)borate‐Functionalized Solvent Polymeric Membrane: A Facile and Sensitive Sensing Platform for Peroxidase and Peroxidase Mimetics

“…For example, the use of fluorous membrane allowing for especially strong ion pair formation and weak interfering ion solvation could elevate the selectivities toward alkylammonium cations over inorganic ions by several orders of magnitude, [40] which may also yield intriguing sensitivities for organic intermediates in the o-PD oxidation. Since potential responses of intermediates are dictated by the ion exchange process across the membranesample interface, the sensitivity could be improved by use of more rigid membrane matrix such as poly(acrylates) to suppress the target ion diffusion into the membrane bulk [41] or a rotating electrode configuration to enhance the transport of target ion from the sample solution into the sample-membrane interface. [42] The regenerability of the intermediate-sensitive SPME is important for its practical use.…”