Reference Electrodes with Polymer-Based Membranes—Comprehensive Performance Characteristics

Abstract

Several types of liquid membrane and solid-state reference electrodes based on different plastics were fabricated. In the membranes studied, equitransferent organic (QB) and inorganic salts (KCl) are dispersed in polyvinyl chloride (PVC), polyurethane (PU), urea-formaldehyde resin (UF), polyvinyl acetate (PVA), as well as remelted KCl in order to show the matrix impact on the reference membranes’ behavior. The comparison of potentiometic performance was made using specially designed standardized testing protocols. A problem in the reference electrode research and literature has been a lack of standardized testing, which leads to difficulties in comparing different types, qualities, and properties of reference electrodes. Herein, several protocols were developed to test the electrodes’ performance with respect to stability over time, pH sensitivity, ionic strength, and various ionic species. All of the prepared reference electrodes performed well in at least some respect and would be suitable for certain applications as described in the text. Most of the reference types, however, demonstrated some weakness that had not been previously highlighted in the literature, due in large part to the lack of exhaustive and/or consistent testing protocols.

Solid-Contact Ion-Selective Electrodes: Response Mechanisms, Transducer Materials and Wearable Sensors

“…(2) In addition to the WE of SC-ISEs, the RE should be given more attention. Currently, polymer-based [92][93][94], ionic liquid-junction [95][96][97], and lipophilic salts modified-polymer [98,99] are the main solid-state REs. Recently, a solid-state RE of Ag/AgI based on a self-referencing pulstrode offers a new strategy [100].…”

Solid-Contact Electrode with Composite PVC-Based 3D-Printed Membrane. Optimization of Fabrication and Performance

“…The potentiometric measurements were performed using a homemade 16-channel set-up. The input impedance was greater than 10 13 Ohms, and the input current was lower than 20 fA for each of the 16 inputs and the reference electrode input. The multi-channel potential-meter was coupled with a personal computer equipped with a 16-bit resolution data acquisition card PCI DAS 6014 (Computer Boards; Norton, MA, USA) or a 16-bit resolution data acquisition card USB1606G (MC Measurements Computing, Norton, MA, USA) and custom-made software.…”

“…Indeed, the materials used and the fabrication technology, the methods of characterization and testing have been, and are, distinctly different, see: [ 7 ]. However, new expectations and a need for ion-monitoring have inspired a boom of interest in designing reference electrodes, which is reflected in numerous reports [ 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 ].…”

“…Of particular importance is the fabrication method of the solid-contact reference electrodes by injection moulding [ 21 ]. For the first time, the application of thermoplastic polymers, such as poly (vinyl acetate) (PVAc) or poly(propylene) (PP), with a high content of equitransferent salts, was demonstrated [ 13 , 15 ]. This method is fast and straightforward, which allows for fabrication in one injection step of the electrodes of different shapes and dimensions.…”

Special Issue “Advances in Artificial and Biological Membranes: Mechanisms of Ionic Sensitivity, Ion-Sensor Designs, and Applications for Ion Measurement”

“…In the very empirical report on plastic membranes with dispersed equitransferent electrolytes, Lingenfelter and co-authors [ 12 ] showed how to obtain the reference electrodes. The research in this area is governed by the idea that there is a wide insensitivity towards ions in the matrices, which is opposite to the aim of ion sensors.…”