Environmental potentiometric sensors sensor selectivity

Ion selective electrodes (ISEs) or, in a wider sense, potentiometric sensors have demonstrated its usefulness to yield information of chemical species in automated and autonomous operation. This feature has fostered their use in the monitoring of numerous processes, in the industrial, clinical and environmental fields, among others. Current practice with these devices relies on sensors with high selectivity only in this way, a simple determination of a single ion is possible in presence of its interferents. Some reluctances on the broadening of their use are surely due to the fact that ISEs are not specific but show high selectivity towards a reduced number of ions. 

The most representative potentiometric sensors are ion-selective electrodes (ISEs), as shown in Fig. 1. They are common in environmental analysis today and some typical ISEs are summarized in Table 1. The measurement of the ion of interest depends on the potential difference across the membrane between the sample solution and the inner reference electrolyte (Fig. 1 left, iimer reference electrode). The membrane potential obtained from the difference between the ISE and the reference electrode (Fig. 1 right,... 

Ion-selective electrodes (ISEs) constitute an example of potentiometric sensors that offer several advantages over other analytical techniques for the analysis of environmentally important ions. Specifically, the sensing platform of a membrane-based ISE consists of an ion carrier (ionophore) entrapped within a liquid polymeric membrane. The membrane does offer some interaction with numerous species, but the main interaction governing the selectivity of the sensor is between the analyte/interferences and the ionophore. Once an ionophore that offers the preferred selectivity has been developed and the polymer components that are ionophore-compatible have been optimized, the production of a functional ISE is rather facile and rapid. Presently, ISEs have been reported for several species including metal ions, anions, surfactants, and gases (5). 

Sulfadimethoxine (SMD) is a dmg frequently used to prevent the spreading of diseases in freshwater fish aquaculture, but its control is important to avoid environmental contamination. A potentiometric sensor selective to SMD was built inside a micropipette tip [211] by immersing a PVC membrane loaded with 1 % of meTO-tetra(phenyl)porphyrinate manganese(lll) chloride in a reference solution. This electrode gave near Nemstian response (54.1 mV/decade) and excellent detection limit (2.4 x 10 mol L ) was attained. For the quantification of SO2, a selective electrode was prepared by incorporation of Cio-(tetraphenyl)porphyr-inate zinc(ll) in a PVC membrane plasticized with 2-nitrophenyl-phenylether [212]. The new electrode presented a selective response to sulphite, with good linearity in an interval larger than four decades of concentration and slope of -59.5 mV per decade, and detection limit of 3.7 x 10 mol L . This sensor presented high... 

Potentiometric ion-selective electrodes (ISEs) are one of the most important gronps of chemical sensors. The application of ISEs has evolved to a well-established rontine analytical technique in many fields, inclnding clinical and environmental analysis, physiology, and process control. The essential part of ISEs is the ion-selective membrane that is commonly placed between two aqueous phases, i.e the sample and inner solutions that contain an analyte ion. The membrane may be a glass, a crystalline solid, or a liquid (1). The potential difference across the membrane is measured with two reference electrodes positioned in the respective aqueous phases... 

An older general review by Stefan et al. [2] considers mathematical modeling for data processing (including a variety of chemometric methods such as linear and nonlinear partial least squares, fuzzy neural networks, and multivariate analysis of variance), designs for electrochemical sensor arrays as well as applications in environmental, food and clinical analysis. Arrays of potentiometric ion-selective electrodes, piezoelectric crystal sensors, and voltammetric biosensors, as well as the electronic nose gas-phase sensor arrays are reviewed. 

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