Amperometric ion-selective electrodes

Y. Yamamoto. Studies on Amperometric Ion-Selective Electrode Sensors. PhD Thesis, Kyoto University, Kyoto 1991. 

Controlled potential methods have been successfully applied to ion-selective electrodes. The term voltammetric ion-selective electrode (VISE) was suggested by Cammann [60], Senda and coworkers called electrodes placed under constant potential conditions amperometric ion-selective electrodes (AISE) [61, 62], Similarly to controlled current methods potentiostatic techniques help to overcome two major drawbacks of classic potentiometry. First, ISEs have a logarithmic response function, which makes them less sensitive to the small change in activity of the detected analyte. Second, an increased charge of the detected ions leads to the reduction of the response slope and, therefore, to the loss of sensitivity, especially in the case of large polyionic molecules. Due to the underlying response mechanism voltammetric ISEs yield a linear response function that is not as sensitive to the charge of the ion. 

M. Senda, H. Katano, and M. Yamada, Amperometric ion-selective electrode. Voltammetric theory and analytical applications at high concentration and trace levels. J. Electroanal. Chem. 468, 34-41 (1999). 

Z. Samec, E. Samcova, and H.H. Girault, Ion amperometry at the interface between two immiscible electrolyte solutions in view of realizing the amperometric ion-selective electrode. Talcmta 63, 21—32 (2004). 

Y. Yamamoto, et. al.. Potassium and sodium ion sensor based on amperometric ion-selective electrode, Bunseki Kakagu, 39 (11), 655-60... 

Extensive studies have been carried out to derive the voltammetric response of the different types of assisted ion transfer for different techniques, such as cyclic voltammetry and differential pulse voltammetry. This part of electrochemistry at soft interfaces has found many applications, mainly for the determination of complexation constants for liquid extraction [4], and these are of interest not only for nuclear reprocessing but also for the development of amperometric ion-selective electrodes [5]. 

Langmaier, J. Trojanek, A. Samec, Z. (2009). Amperometric Ion-Selective Electrode for alkali metal cations based on a room-temperature ionic liquid membrane. Ekctroanalysis, 21,1977-1983. 

Ion-selective electrodes and amperometric ceUs have had a long history of success in a wide variety of appHcations (8,9). A microelectronics-inspired revolution is also occurring in these devices, brought about by the advent of photoHthographicaHy defined arrays of microelectrodes on planar substrates... 

The duration of the response results primarily from the rate of elution of the sample, and not on any inherent limitation in the response time of the electrode. This is a characteristic of ion-selective electrodes, but amperometric responses depend not only on the duration of elution but also on flow rate because of the hydrodynamic effects discussed previously. 

Studies of the polarized IBTILE provide a fundamental knowledge that makes it possible to explain phenomena occurring at the membranes of ion-selective electrodes. In addition, the rates of ion transfer and assisted ion transfer reactions are proportional to concentrations, which is a basis of an amperometric ion-selective (sensitive) electrode. 

S. Sawada, H. Torii, T. Osakai, and T. Kimoto, Pulse amperometric detection of lithium in artificial serum using a flow injection system with a liquid/liquid-type ion-selective electrode. Anal. Chem. 70, 4286-4290 (1998). 

Sensor A device having a response (ideally) for one particular analyte. Poten-tiometric sensors are typically ion-selective electrodes, while amperometric sensors rely on Faraday s laws. 

Figure 1.11 — Average number of papers on (bio)chemical sensors published annually, based on data from Janata s biannual review. E electrochemical sensors ISEs ion-selective electrodes P potentiometric sensors A amperometric sensors C conductimetric sensors O optical sensors M mass sensors T thermal sensors. (Adapted from [23] with permission of the American Chemical Society).

The use of dual-electrode amperometric detectors provides advantages in sensitivity and detection limits. Series configuration and parallel configuration are both possible. Ion-selective electrodes allow the selective quantification of selected analytes even in complex matrices. 

Electrochemical ion-selective sensors (ISSs), including potentiometric ion-selective electrodes (ISEs) and potentiometric or amperometric gas-selective sensors (GSSs), attracted the interest of clinical chemistry because they offer fast, reliable, inexpensive analytical results in service-free automated analyzers. In this way, the electrochemical sensors satisfy the present demands of central hospital laboratories and peripheral point-of-care medical service points, such as bedside, emergency or first-contact healthcare centers. 

The scope of ion-selective electrodes (ISEs) has been greatly enhanced by employing a poly(vinyl chloride) matrix to entangle sensor cocktail materials. Fbr ISFET devices an in situ photopolymerisation of monobutyl methacrylate provides a viable poly(butyl methacrylate) calcium sensor film with good gate adhesion properties. One or more enzymes can be chemically immobilized on modified nylon mesh. The resultant matrices are suitable for the amperometric assay of carbohydrates in blood and food products. 

The electrochemical analyzers are another important family of liquid analyzers. They include potentiometric, wherein an electric potential is measured and the solution remains unchanged conductive, in which a minute current is measured but the system is essentially unchanged and amperometric, in which a chemical reaction occurs during the course of the measurement. Potentiometric analyzers can measure the presence of dissolved ionized solids in a solution. These measurements include pH, oxidation-reduction potential (ORP), and ion-selective electrodes (ISEs) or probes. 

Osakai et al. used a microcomputer-controlled system for the ion transfer voltammetry procedure [20]. The system used is based on a NEC PC-9801 microcomputer, which was designed by using a polarizable oil-water interface as an ion-selective electrode surface. The system was applied to the determination of acetylcholine ion by cyclic, differential pulse, and normal pulse voltammetry at the PVC-nitrobenzene gel electrode. The amperometric measurement was carried out with voltage pulses of short durations and constant amplitude. 

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