title: Paper-based potentiometric ion sensing.
abstract: This 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.
authors.affiliation: Department of Chemistry and Chemical Biology, Harvard University , 12 Oxford Street, Cambridge, Massachusetts 02138, United States.
authors.forename: Wen-Jie
authors.initials: WJ
authors.lastname: Lan
authors.forename: Xu U
authors.initials: XU
authors.lastname: Zou
authors.forename: Mahiar M
authors.initials: MM
authors.lastname: Hamedi
authors.forename: Jinbo
authors.initials: J
authors.lastname: Hu
authors.forename: Claudio
authors.initials: C
authors.lastname: Parolo
authors.forename: E Jane
authors.initials: EJ
authors.lastname: Maxwell
authors.forename: Philippe
authors.initials: P
authors.lastname: Bühlmann
authors.forename: George M
authors.initials: GM
authors.lastname: Whitesides
mesh_terms: D017736:Ion-Selective Electrodes; D010209:Paper; D011199:Potentiometry / Q000379:methods*