Lan, Wen-JieZou, Xu U.Hamedi, Mahiar MaxHu, JinboParolo, ClaudioMaxwell, E. JaneBühlmann, PhilippeWhitesides, George2015-06-292014Lan, Wen-Jie, Xu U. Zou, Mahiar M. Hamedi, Jinbo Hu, Claudio Parolo, E. Jane Maxwell, Philippe Bühlmann, and George M. Whitesides. 2014. “Paper-Based Potentiometric Ion Sensing.” Analytical Chemistry 86 (19) (October 7): 9548–9553. doi:10.1021/ac5018088.0003-2700http://nrs.harvard.edu/urn-3:HUL.InstRepos:16883005This paper describes the design and fabrication of ion-sensing electrochemical paper-based analytical devices (EPADs) in which a miniaturized paper reference electrode is integrated with a small ion-selective paper electrode (ISPE) for potentiometric measurements. Ion-sensing EPADs use printed wax barriers to define electrochemical sample and reference zones. Single-layer EPADs for sensing of chloride ions include wax-defined sample and reference zones that each incorporate a Ag/AgCl electrode. In EPADs developed for other electrolytes (potassium, sodium, and calcium ions), a PVC-based ion-selective membrane is added to separate the sample zone from a paper indicator electrode. After the addition of a small volume (less than 10 μL) of sample and reference solutions to different zones, ion-sensing EPADs exhibit a linear response, over 3 orders of magnitude, in ranges of electrolyte concentrations that are relevant to a variety of applications, with a slope close to the theoretical value (59.2/z mV). Ion-selective EPADs provide a portable, inexpensive, and disposable way of measuring concentrations of electrolyte ions in aqueous solutions.en-USJournal Article2015-06-2910.1021/ac5018088