On the example of a colorimetric sodium assay, this work demonstrates the implementation of a classical cation-exchange optode relying on an ionophore-doped plasticized PVC membrane into a paper-based analytical device (PAD). An ion-selective optode (ISO) system has been arranged into a vertically-assembled PAD (vPAD) integrating a pH-buffering function. Capillary force-driven sample liquid transportation through the paper matrix enabled pH-adjustment prior to the optical detection of the analyte cation. Functionalized paper layers with inkjet-deposited ISO membranes were combined with whole device lamination to attain a stable ion-exchange equilibrium required for the theoretical behavior of ISOs. Whole device lamination limited rapid evaporation of sample liquid on vPADs to avoid an increase of target concentration. Sigmoidal response curves between 10⁻⁵ and 1 M of Na⁺ at pH 5.0–7.0 have been confirmed on vPADs, following the theory defined by the cation-exchange equilibrium reaction. Finally, the influence of the cellulosic paper substrate matrix acting as a cation-exchanger on the optode response behavior has been evaluated and compared with conventional plastic film optodes.

中文翻译：

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将增塑的基于PVC的阳离子选择性光电二极管系统实施到用于比色钠检测的纸基分析设备中†

在比色钠测定的例子中，这项工作证明了经典的阳离子交换光电极的实现，该离子交换光电极依靠离子载体掺杂的增塑的PVC膜进入基于纸张的分析装置（PAD）中。离子选择光电（ISO）系统已被安排到具有pH缓冲功能的垂直组装的PAD（vPAD）中。毛细管力驱动的样品液体通过纸质基质传输之前，可以在光学检测分析物阳离子之前进行pH调节。将具有喷墨沉积ISO膜的功能化纸层与整个设备层压结合在一起，以获得ISO理论行为所需的稳定离子交换平衡。整个设备的层压限制了vPAD上样品液体的快速蒸发，从而避免了目标浓度的增加。遵循阳离子交换平衡反应定义的理论，已在vPAD上证实了pH为5.0-7.0的Na ^{+ -5}和1M。最后，已评估了纤维素纸基材基质作为阳离子交换剂对光电二极管响应行为的影响，并将其与常规塑料薄膜光电二极管进行了比较。