All-Solid-State Reference Electrodes Based on Colloid-Imprinted Mesoporous Carbon and Their Application in Disposable Paper-based Potentiometric Sensing Devices

• Published in: Analytical chemistry (Washington) 2015-03, Vol.87 (5), p.2981-2987
• Main Authors: Hu, Jinbo, Ho, Kieu T, Zou, Xu U, Smyrl, William H, Stein, Andreas, Bühlmann, Philippe
• Format: Article
• Language: English
• Subjects: Carbon; Colloids; Computer integrated manufacturing; Contact; Electrodes; Joining; Membranes; Porosity; Sensing devices; Solids
• ISSN: 0003-2700; 1520-6882
• DOI: 10.1021/ac504556s

Reference electrodes are used in almost every electroanalytical measurement. Here, all-solid-state reference electrodes are described that employ colloid-imprinted mesoporous (CIM) carbon as solid contact and a poly­(vinyl chloride) reference membrane to contact the sample. Such a reference membrane is doped with a moderately hydrophilic ionic liquid and a hydrophobic redox couple, leading to well-defined constant potentials at the interfaces of this membrane to the sample and to the solid contact, respectively. Due to the intrinsic properties of CIM carbon, reference electrodes with a CIM carbon solid contact exhibit excellent resistance to common interfering agents such as light and O2, with outstanding potential stability in continuous potentiometric measurements. The potential drift of CIM carbon-based reference electrodes without redox couple is as low as 1.7 μV/h over 110 h, making them the most stable all-solid-state reference electrodes reported so far. To demonstrate the compatibility of CIM carbon-based reference electrodes with miniaturized potentiometric systems, these reference electrodes were integrated into paper-based potentiometric sensing devices, successfully replacing the conventional reference electrode with its reference electrolyte solution. As a proof of concept, disposable paper-based Cl– sensing devices that contain stencil-printed Ag/AgCl-based Cl– selective electrodes and CIM carbon-based reference electrodes were constructed. These sensing devices are inexpensive, easy to use, and offer highly reproducible Cl– measurements with sample volumes as low as 10 μL.