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 PVCbased 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.

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

“…10,11 A recent example that demonstrates the difficulty of integrating conventional reference electrodes into affordable and disposable sensing devices is that of the paper-based ion sensors that were recently developed for the analysis of Cl -, K + , Na + , and Ca 2+ . 12 Different from other paper-based potentiometric sensors where paper was used either as a substrate to mechanically support the solid contact [13][14][15][16] or as a microfluidic sampling tool, 17 wax-imprinted paper used in this design served as a substrate to support the electrodes, the reference electrolyte, and the sample. Although highly miniaturized, these ion sensors still employed a conventional reference system that contained a stencil-printed Ag/AgCl electrode coupled with a KCl solution as reference electrolyte.…”

Thin Layer Samples Controlled by Dynamic Electrochemistry

“…Paper has been widely used as sampling element in microfluidic paper-based analytical devices. [21] However, its ability to create a well-defined thin aqueous layer has not yet explored in electrochemical sensor design.…”

A Paper-Based “Pop-up” Electrochemical Device for Analysis of Beta-Hydroxybutyrate

“…26,28,30–35 We have also incorporated ion-selective membranes into these devices to make ion-selective electrodes. 36 These EPADs can perform a wide range electrochemical methods (e.g., potentiometry, voltammetry, chronoamperometry, and coulometry) to detect a variety of analytes. 14,32,36–44 …”