Influence of Ionic Liquids on the Selectivity of Ion Exchange-Based Polymer Membrane Sensing Layers

Deep Eutectic Solvents Enhance Stability of Ag/AgCl Solid State Miniaturised Reference Electrode

A new class of solid-state miniaturised reference electrodes with a deep eutectic solvent as an alternate enhancement electrode system is described. A simple and accurate stable electrochemical sensor was prepared by developing a conventional reference electrode using an Ag/AgCl planar micro-reference electrode covered with a PVC polymer. A conductive deep eutectic solvent (DES), ethaline, was added in small quantities and mixed with an internal electrolyte to maintain the Cl− ion concentration in the constructed electrode. The fabricated microelectrode showed good stability, reproducibility, and long-term stability against varying concentrations of different ions. The potential response of the fabricated microelectrode was studied under varying concentrations of Cl− ions in the presence of 0.1 to 1.0% DES in a concentrated electrolyte system (20 mM Na2SO4). The stability of the fabricated microelectrode was addressed against Br− and Cl− ions using different inorganic salts, and the potential measurements were found to be insensitive toward all responsive ions. The stability response of the fabricated microelectrode against Cl− ions was optimised in the presence of 1.0% DES. The experimental data showed good agreement with the potential change of the fabricated electrode in the presence of the supporting DES electrolyte. The liquid junction-free PVC solid-state miniaturised reference electrode demonstrated a constant potentiometric measurement over a long period of time. The concentrated supporting DES electrolyte solution (20 mM) exhibited better stability values and was a more suitable fabricated microelectrode than other additive concentrations. The long-term stability of the developed microelectrode displayed a good lifetime and high stability of around 60 days.

Organic Bioelectronic Devices for Metabolite Sensing

Electrochemical detection of metabolites is essential for early diagnosis and continuous monitoring of a variety of health conditions. This review focuses on organic electronic material-based metabolite sensors and highlights their potential to tackle critical challenges associated with metabolite detection. We provide an overview of the distinct classes of organic electronic materials and biorecognition units used in metabolite sensors, explain the different detection strategies developed to date, and identify the advantages and drawbacks of each technology. We then benchmark state-of-the-art organic electronic metabolite sensors by categorizing them based on their application area (in vitro, body-interfaced, in vivo, and cell-interfaced). Finally, we share our perspective on using organic bioelectronic materials for metabolite sensing and address the current challenges for the devices and progress to come.

Simultaneous Detection of Ammonium and Nitrate in Environmental Samples Using on Ion-Selective Electrode and Comparison with Portable Colorimetric Assays

Simple, robust, and low-cost nitrate- and ammonium-selective electrodes were made using substrate prepared from household materials. We explored phosphonium-based ILs and poly (methyl methacrylate)/poly(decyl methacrylate)(MMA-DMA) copolymer as matrix materials alternative to classical PVC-based membranes. IL-based membranes showed suitability only for nitrate-selective electrode exhibiting linear concentration range between 5.0 × 10^-6 and 2.5 × 10^-3 M with a detection limit of 5.5 × 10^-7 M. On the other hand, MMA-DMA-based membranes showed suitability for both ammonium- and nitrate-selective electrodes, and were successfully applied to detect NO₃^- and NH₄⁺ in water and soil samples. The proposed ISEs exhibited near-Nernstian potentiometric responses to NO₃^- and NH₄⁺ with the linear range concentration between 5.0 × 10^-5 and 5.0 × 10^-2 M (LOD = 11.3 µM) and 5.0 × 10^-6 and 1.0 × 10^-3 M (LOD = 1.2 µM), respectively. The power of ISEs to detect NO₃^- and NH₄⁺ in water and soils was tested by comparison with traditional, portable colorimetric techniques. Procedures required for analysis by each technique from the perspective of a non-trained person (e.g., farmer) and the convenience of the use on the field are compared and contrasted.