Solid-Contact Potentiometric Anion Sensing Based on Classic Silver/Silver Insoluble Salts Electrodes without Ion-Selective Membrane

Abstract

Current solid potentiometric ion sensors mostly rely on polymeric-membrane-based, solid-contact, ion-selective electrodes (SC-ISEs). However, anion sensing has been a challenge with respect to cations due to the rareness of anion ionophores. Classic metal/metal insoluble salt electrodes (such as Ag/AgCl) without an ion-selective membrane (ISM) offer an alternative. In this work, we first compared the two types of SC-ISEs of Cl− with/without the ISM. It is found that the ISM-free Ag/AgCl electrode discloses a comparable selectivity regarding organic chloride ionophores. Additionally, the electrode exhibits better comprehensive performances (stability, reproducibility, and anti-interference ability) than the ISM-based SC-ISE. In addition to Cl−, other Ag/AgX electrodes also work toward single and multi-valent anions sensing. Finally, a flexible Cl− sensor was fabricated for on-body monitoring the concentration of sweat Cl− to illustrate a proof-of-concept application in wearable anion sensors. This work re-emphasizes the ISM-free SC-ISEs for solid anion sensing.

A Solid-Contact Reference Electrode Based on Silver/Silver Organic Insoluble Salt for Potentiometric Ion Sensing

“…The flexible SC-RE was finally conditioned in 10 –5 M NaCl solution overnight before use. For the working electrode of Cl – -SC-ISEs, the process is similar to a previous work . The sputtered Ag electrode was further oxidized in 0.05 M FeCl 3 for 10 s to obtain the flexible Ag/AgCl electrode for sweat Cl – detection.…”

“…For the working electrode of Cl − -SC-ISEs, the process is similar to a previous work. 42 The sputtered Ag electrode was further oxidized in 0.05 M FeCl 3 for 10 s to obtain the flexible Ag/AgCl electrode for sweat Cl − detection. Three Cl − -SC-ISEs were fabricated in parallel, which could simultaneously measure the concentration of sweat Cl − .…”

New Materials Used for the Development of Anion-Selective Electrodes—A Review

“…A comparison of the analytical parameters of various perchlorate electrodes is presented in Table 4. Two kinds of electrodes differing in the type of layer providing sensitivity to chloride ions were reported in [57]. One of the electrodes had an ion-selective membrane with chloride ionophore(I) (Figure 10b), which was applied to an Ag|AgCl electrode, while the other ISE was a classical silver chloride electrode without an ionophore and ISM.…”

Recent Advances in Wearable Potentiometric pH Sensors

“…At present, the reported entities that can be detected by wearable bio(chemical)sensors involve multiple species, including pH, Na + , K + , Ca 2+ , NH 4 + , Cl − , glucose, dopamine, urea, etc. [ 1 , 5 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 ]. Among them, the detection of pH is particularly significant—it is used as a routine indicator because it participates in most biochemical reactions in the human body [ 32 , 33 , 34 ].…”