Various embodiments of the disclosure provide reference electrodes for use in electrochemical systems (e.g., electrochemical cells) that use molten salt media as the electrolyte of choice. The reference electrodes include a metal core with an outer, solid layer of the metal's oxide, silicide, or carbide. The oxide, silicide, or carbide outer layer may be formed uniformly and with sufficient durability to withstand exposure to molten salt material. The outer layer may be formed by processes configured to form (e.g., grow) the oxide, silicide, or carbide layer directly on the outer surface of the metal core with uniformity of the layer's composition and thickness all along the outer surface of the metal core. Related electrochemical systems are also disclosed.

A reference electrode which is stable over a wide range of temperatures, pressures and chemical conditions is provided. The subject reference electrode according to the present invention comprises a tubular enclosure composed of quartz having a distal, closed end and a proximal, open end. An insulating ceramic rod is seemingly connected to the opening in the closed distal end of the enclosure to form micro-cracks between the ceramic rod and the quartz enclosure (called a cracked junction, CJ). The CJ gives a very tortuous path for ion conduction from inside the reference electrode (RE) to a working electrode (WE). Inside the tubular enclosure is an electrical lead (e.g., a silver wire) disposed in an electrolyte comprising a mixture of alkaline metal salts (e.g., AgCl and KCl), extending from the electrolyte upward through a sealing means at the proximal end of the quartz enclosure.

A sensor element includes: a main pump cell constituted by an inner pump electrode facing a first inner space into which a measurement gas is introduced, an external pump electrode provided on an element surface, and a solid electrolyte located therebetween; and a measurement pump cell constituted by the measurement electrode facing a second inner space which is communicated with the first inner space and functioning as a reduction catalyst for NOx, and a solid electrolyte located therebetween. The inner pump electrode has a planar shape in which two parts of a front end part relatively having a large area and a rear end part relatively having a small area are sequentially connected in this order from an upstream side in a longitudinal direction of the sensor element while satisfying requirements of a predetermined size and area.

An ion selective electrode (ISE) assembly may be installed within a sample path of a biological testing system to measure ion concentration within sample fluid flowing through the sample path. A transducer membrane is placed within a housing and positioned to contact the sample path. A threaded portion is advanced into a socket of the housing and forces the membrane against a sealing portion of the sample path to prevent retention of sample fluid within the housing after testing. Sealing may be accomplished without adhesives or sealants and instead relies upon mechanical pressure of the threaded portion. Another implementation includes a reference measuring electrode and several ion measuring electrodes combined into a single housing. Another implementation includes a reference measuring electrode and several ion measuring electrodes combined into a cartridge that includes a sample well instead of a sample path.

A smart sensor system is provided which uses a monitoring electrode to produce a calibration output that can be used in-situ and in real-time to monitor and address reference electrode drift and to provide information regarding sensor operation. The monitoring electrode uses a redox chemistry that is either a non-active redox species that is not sensitive to changes in a solution being tested/monitored or a redox active species that sets a pH of the local environment proximal to the electrode when the electrode is contacted with a test and/or reference solution. The smart sensor system includes at least one of a solid-state electrochemical sensor; a glass electrode, a reduction oxidation sensor; and/or a glucose sensor and/or a sensor to monitor constituent parts of the solution composition.

A pH sensor for detecting a pH of a sample includes a reference electrode and a glass electrode. The reference electrode includes a hollow tubular housing, and at least one water absorbing unit disposed in the housing and including a porous junction member configured to contact the sample, and a water absorbing member disposed on one side of the porous junction member that is opposite to the sample. The water absorbing member is made by soaking a superabsorbent polymer in potassium chloride solution. The glass electrode is inserted into the water absorbing member, and protrudes from the junction member toward the sample.

ISEs comprising a substrate layer; a carbon nanotube layer disposed on the substrate layer; a conductive metal layer on a portion of the carbon nanotube layer; a conductive polymer disposed on the portion; and an ion-selective membrane disposed on the conductive polymer and methods of making them are provided. A system is also provided for detecting a plurality of analyte ions in a sample comprising a housing; a plurality of ISEs associated with the housing, each electrode comprising an ion-selective membrane to a different analyte ion; a reference electrode associated with the housing; a fluid sample receptacle associated with the housing and in fluid communication with the plurality of ion-selective electrodes and reference electrode.

Embodiments of the invention are directed to a system for detecting neurotransmitters. A non-limiting example of the system includes a porous electrode. A system can also include a pH sensor attached to the porous electrode, wherein the pH sensor includes a sensing electrode and a reference electrode. The system can also include electronic circuitry in communication with the pH sensor.

Systems and methods described herein include a reference electrode for being immersed in a bulk solution. The reference electrode comprises a reservoir having reservoir walls defining a reservoir volume filled with an electrolyte; an electrode in the reservoir, in contact with the electrolyte. The reservoir of the reference electrode is closed except for the presence of at least one pore in at least one of the reservoir walls, the at least one pore being filled with electrolyte and being adapted for allowing ionic contact between the electrolyte in the reservoir and the bulk solution into which the reference electrode is to be immersed.

Provided is a gas sensor which is capable of preferably sensing an ammonia gas, and has excellent durability. A mixed-potential gas sensor includes a sensor element composed of an oxygen-ion conductive solid electrolyte, and a heater provided inside the element. The sensor element includes on a surface thereof a sensing electrode formed of a cermet including Pt, Au and an oxygen-ion conductive solid electrolyte, and also includes a reference electrode formed of a cermet of Pt and an oxygen-ion conductive solid electrolyte, and a porous electrode protective layer whose porosity is 5 to 40% covering at least the sensing electrode. The Au abundance ratio in a surface of noble metal particles forming the sensing electrode is 0.4 or more. The concentration of an ammonia gas is determined on the basis of a potential difference occurring between the sensing electrode and the reference electrode when the sensor element is disposed in a measurement gas and heated to 400 C. to 800 C.