Potentiometric sensors solid-state electrode

Ramirez-Salgado, J. and Fabry, P. (2003) Study of CO2 electrodes in open devices of potentiometric sensors. Solid State Ionics,... 

Potentiometric Sensors Inthe field of ion-selective electrodes, considerable progress has been achieved in the last few years. By buffering the primary ions concentration on a low level in the internal solution, ionic fluxes in the membrane are affected [424-426]. Thus, primary ion leakage into sample solution is hindered, resulting in a tremendous shift of detection limits to lower values for Pb +-selective electrodes, the detection limit up to 10 M level has been achieved for internal solution electrodes [424, 427] and below 10 M for all-solid-state electrodes with conducting polymer solid... 

Amperometric sensing of gases is based on solid ion-conducting materials, as described for potentiometric gas sensors. Solid-state amperometric gas sensors measure the limiting current (ij) flowing across the electrochemical cell upon application of a fixed voltage so that the rate of electrode reaction is controlled by the gas transport across the cell. The diffusion barrier consists of small-hole porous ceramics. The limiting current satisfies the relationship ... 

The general trend to miniaturize chemical sensors and to make them cheap and easier for handling has led to the development of potentiometric sensors with solid internal contact. This class of sensors includes different types of solid-state electrodes, solid-state contact, and coated wire electrodes as well as ion-selective field-effect transistors (FETs). 

The majority of solid electrolyte sensors are based on proton conductors (Miura et al. 1989, Alberti and Casciola 2(X)1). Metal oxides that can potentially meet the requirements for application in solid electrolyte sensors are listed in Table 2.7. These proton condnctors typically do not have high porosity but rather can reach 96-99% of the theoretical density (Jacobs et al. 1993). Similar to oxygen sensors, solid-state electrochemical cells for hydrogen sensing are typically constructed by combining a membrane of solid electrolyte (proton conductor) with a pair of electrodes (electronic conductors) Most of the sensors that use solid electrolytes are operated potentiometrically. The voltage produced is from the concentration dependence of the chenucal potential, which at eqnihbrium is represented by the Nemst equation (Eq. 2.3). 

Zosel J, Schiffel G, Gerlach F, Ahlbom K, Sasum U, Vashook V, Guth U (2006) Electrode materials for potentiometric hydrogen sensors. Solid State Ionics 177 2301-2304... 

A PT-modified vitreous carbon electrode can be used as a universal response potentiometric sensor. This all-solid-state electrode is readily prepared, responds rapidly, and has good stability and reproducibility [798]. A potentiometric iodide sensor based on a PMT film electrode has been developed. This... 

Keywords Poly(vinyl) chloride, potentiometric sensors, polymer membrane, liquid contact electrodes, solid-state electrodes, determination of anti-inflammatory drugs, pharmaceutical... 

Metal/metal oxides are the materials of choice for construction of all-solid-state pH microelectrodes. A further understanding of pH sensing mechanisms for metal/metal oxide electrodes will have a significant impact on sensor development. This will help in understanding which factors control Nemstian responses and how to reduce interference of the potentiometric detection of pH by redox reactions at the metal-metal oxide interface. While glass pH electrodes will remain as a gold standard for many applications, all-solid-state pH sensors, especially those that are metal/metal oxide-based microelectrodes, will continue to make potentiometric in-vivo pH determination an attractive analytical method in the future. 

J. Bobacka. T. Lindfors, A. Lewenstam. and A. Ivaska, All-Solid-State Ion Sensors Using Conducting Polymers as Ion-to-Electron Transducers, Am. Lab., February 2004, 13 A. Konopka, T. Sokalski, A. Michalska, A. Lewenstam, and M. Maj-Zurawska, Factors Affecting the Potentiometric Response of All-Solid-State Solvent Polymeric Membrane Calcium-Selective Electrode for Low-Level Measurement, Anal. Chem. 2004, 76, 6410 M. Fouskaki and... 

Traditionally, potentiometric sensors are distinguished by the membrane material. Glass electrodes are very well established especially in the detection of H+. However, fine-tuning of the potentiometric response of this type of membrane is chemically difficult. Solid-state membranes such as silver halides or metal sulphides are also well established for a number of cations and anions [25,26]. Their LOD is ideally a direct function of the solubility product of the materials [27], but it is often limited by dissolution of impurities [28-30]. Polymeric membrane-based ISEs are a group of the most versatile and widespread potentiometric sensors. Their versatility is based on the possibility of chemical tuning because the selectivity is based on the extraction of an ion into a polymer and its complexation with a receptor that can be chemically designed. Most research has been done on polymer-based ISEs and the remainder of this work will focus on this sensor type. 

In order to fully utilize solid-state ion sensors in potentiometric measurements there is a need for a durable and reliable solid-state reference electrode as well. It was shown recently that it is possible to construct... 

Improvement of the geometric structure of the working electrode by a well-controlled PEVD process benefits the performance of a CO sensor in many ways. To optimize kinetic behavior, the response and recovery times of CO potentiometric sensors were studied at various auxiliary phase coverages. This was realized by a unique experimental arrangement to deposit the Na COj auxiliary phase in-situ at the working electrode of type III potentiometric CO sensors by PEVD in a step-wise fashion. Since the current and flux of solid-state transported material in a series of PEVD processes can be easily moiutoredto control the amount of deposit... 

The mechanism of functioning of potentiometric chemical sensors, of which most commonly are developed and used membrane ion-selective electrodes (ISE), is based on change of distribution of ions on the interface membrane-electrolyte. Thus, there are designed solid-state and plasticized membrane of different chemical composition, which can be tailored to choose and transport ions with a selected... 

Solid-state reference electrodes for potentiometric sensors are currently under research. The main problem to be faced in developing this type of electrode lies in connecting the ionic conducting (usually aqueous) solution with an electronic conductor. Since the reference electrode has to maintain a defined potential, the electrochemical reaction with components of the electrolyte has to be avoided. Oxides, mixed oxides, and polyoxometalate salts of transition elements can be proposed for preparing solid-state reference electrodes. Tested compounds include tungsten and molybdenum oxides (Guth et al., 2009). 

Guth, U., Gerlach, E, Decker, M., Oelssner, W, and Vonau, W. 2009. Solid-state reference electrodes for potentiometric sensors. Journal of Solid State Electrochemistry 13, 27-39. 

Solid-state electrochemistry, as a subsection of electrochemistry, emphasizes phenomena in which the properties of sohds play a dominant role. This includes phenomena involving ionically and/or electronically conducting phases (e.g., in potentiometric or conductometric chemical sensors). As far as classical electrochemical cells are concerned, one refers not only to all-solid-state cells with sohd electrolytes (e.g., ceramic fuel cells), but also to cells with hquid electrolytes, such as modern Li-based batteries in which the storage within the sohd electrode is crucial [1-3]. 

Holzinger, M., Maier, J. and Sitte, W. (1996) Fast CO2-selective potentiometric sensor with open reference electrode. Solid State Ionics, 86-88, 1055-62. 

Wachsman, E.D. (2003) Selective potentiometric detection of NOx ky differential electrode equilibria. Proceedings of the Electrochemical Society, 2000-32 Solid-State Ionic Devices II Ceramic Sensors, The Electrochemical Society, Penrrington, New Jersey, pp. 215-21. 

Potentiometry—the measurement of electric potentials in electrochemical cells—is probably one of the oldest methods of chemical analysis still in wide use. The early, essentially qualitative, work of Luigi Galvani (1737-1798) and Count Alessandro Volta (1745-1827) had its first fruit in the work of J. Willard Gibbs (1839-1903) and Walther Nernst (1864-1941), who laid the foundations for the treatment of electrochemical equilibria and electrode potentials. The early analytical applications of potentiometry were essentially to detect the endpoints of titrations. More extensive use of direct potentiometric methods came after Haber developed the glass electrode for pH measurements in 1909. In recent years, several new classes of ion-selective sensors have been introduced, beginning with glass electrodes more or less selectively responsive to other univalent cations (Na, NH ", etc.). Now, solid-state crystalline electrodes for ions such as F , Ag", and sulfide, and liquid ion-exchange membrane electrodes responsive to many simple and complex ions—Ca , BF4", CIO "—provide the chemist with electrochemical probes responsive to a wide variety of ionic species. 

The common element in all the electrochemical solid-state CO2 sensors is the solid electrolyte as an ionic conductor. According to the way the measurement is performed, they can be classified into two groups amperimetric and potentiometric. Electrochemical sensors for CO2 detection are usually mixed potential sensors, a subcategory of potentiometric sensors to detect other gases than oxygen. The mixed potential sensors generally involve oxide semiconductors as electrode materials. 

PPy is known to exhibit anionic or cationic potentiometric responses depending on the doping ion. PPy films doped with mobile inorganic anions show anionic sensitivity, while PPy films doped with anions of low mobility such as sulfate, large organic anions, or polyanions show cationic sensitivity. This bifunctionality of ionic and redox sensitivity makes PPy apphcable as an all-sohd-state, ion-selective electrode. All-solid-state, potentiometric PPy sensors were developed for potassium and sodium sensing, which showed better response time, selectivity and most importantly long-term stabihty than the coated wire electrode [130]. 

---