Ion‐Selective Electrode Potentiometry in Environmental Analysis

Abstract

This review will illustrate how it is possible to develop ion-selective electrode (ISE) methodologies that meet the stringent requirements (i.e., high selectivities and very low detection limits) for the analysis of important analytes in the environment, and will present a variety of examples on the application of ISEs in environmental analysis. Despite the experimental biases that have limited the analytical performance of ISEs through apparently high detection limits and modest selectivities, there has been a plethora of research in the application of ISEs in the monitoring of environmentally important trace metals and anions in natural waters and soils. Most popular has been the analysis of free metals in natural waters, as this parameter is known to be a master variable in the uptake and toxicology of trace metals on aquatic biota reflecting the bioavailability of trace metals in the environment. Furthermore, as copper is a major trace metal in coastal waters due to its extensive use in antifouling paints on sea vessels and structures, there are many reports in the literature on the use of the copper ISE in assays of either free copper or the copper complexing capacity of natural waters and soil peats. Moreover, there have been a variety of studies showing a strong correlation between free copper levels and the toxicity of copper on a variety of marine and fresh water organisms. Nevertheless, there are numerous reports in the literature that have used ISEs to monitor important anions such as fluoride, phosphate, sulfate, nitrate, nitrite, chloride, cyanide, etc., as well as other important cations such as ammonium and chromium(VI) in waste and natural waters. In conclusion, this review will present new and interesting perspectives on the application of ISEs in environmental analysis using approaches such as real-time remote monitoring of water quality, shipboard monitoring of environmentally important analytes using flow analysis instrumentation, the use of robust all-solid-state ISEs in submersible instruments for long-term deployment in the field, and innovative analytical approaches such as backside calibration and switchtrodes that avoid standard addition analysis and the concomitant perturbation in analyte speciation in natural samples.

Properties and Customization of Sensor Materials for Biomedical Applications

“…Low-power chemo-and biosensing devices capable of monitoring clinically important parameters in real time represent a great challenge in the analytical field as the issue of sensor calibration pertaining to keeping the response within an accurate calibration domain is particularly significant (1)(2)(3)(4). Diagnostics, personal health, and related costs will also benefit from the introduction of sensors technology (5)(6)(7).…”

“…Santafé et al (113) 4 ] on glucose oxidase activity were also noticed, and this enhancement was employed to perform sensitive chemiluminescent glucose detection (LOD ¼ 4 mM) at pH 8.0 (113).…”

“…ILs can be classified within seven different families on the basis of the ionic structure (91), and typical cations are shown in Figure 2. Their properties depend dramatically on the cation-anion combination (83) and in this sense can be thought as 'designer' or 'fine-tunable' (92) as polarity, viscosity, thermal stability, conductivity, and solvent capacity can be tailored by thoughtful choice of cations and anions (85,93 4 ] is water soluble (94).…”

Electrochemical techniques and sensors for ocean research

“…In an excellent review (De Marco et al, 2007) describe the applications of ion Table 2. Overview of electrochemical techniques.…”

“…Many potential selective electrodes rely on solid state membranes to provide selectivity. The best known is the glass electrode for protons but similar electrodes exist for sodium and fluoride (De Marco et al, 2007). Glass selective microelectrodes were popular with biologists in the early days of intracellular measurements (Thomas, 1979) and although it is still possible to find dedicated instruments such as micro-forges to prepare them, they tend to be replaced by selective cocktails of ionophores or liquid ion exchange resins.…”