Halide sensor

Jayaraman, S., Haggie, P., Wachter, R. M., Remington, S. J. and Verkman, A. S. (2000). Mechanism and cellular applications of a green fluorescent protein-based halide sensor. J. Biol. Chem. 275, 6047-50. 

Beyer T., Hahn P., Hartwig S., Konz W., Scharring S., Katzir A., Steiner H., Jakusch M., Kraft M., Mizaikoff B.,, Mini spectrometer with silver halide sensor fiber for in situ detection of chlorinated hydrocarbons, Sensors Actuators B, 2003 90 319 - 323. 

Sequence-specific biosensor, 183, 185 Selectivity, 92, 143, 147, 155 Selectivity coefficient, 143 Self-assembled monolayers, 39, 118 Selenium, 85 Sensor, 171 Silver halide, 159 Simulation, 35... 

Urbano E., Offenbacher H., Wolfbeis O.S., Optical Sensor for Continuous Determination of Halides, Anal. Chem. 1984 56 427. 

Goebel R., Krska R., Kellner R., Katzir A., Development of Protective Polymer-Coatings for Silver-Halide Fibers and Their Application as Threshold Level Sensors for Chlorinated Hydrocarbons in Sea-Water, Fresenius J. Anal. Chem. 1994 348 780-781. 

The design of fluorescent sensors is of major importance because of the high demand in analytical chemistry, clinical biochemistry, medicine, the environment, etc. Numerous chemical and biochemical analytes can be detected by fluorescence methods cations (H+, Li+, Na+, K+, Ca2+, Mg2+, Zn2+, Pb2+, Al3+, Cd2+, etc.), anions (halide ions, citrates, carboxylates, phosphates, ATP, etc.), neutral molecules (sugars, e.g. glucose, etc.) and gases (O2, CO2, NO, etc.). There is already a wide choice of fluorescent molecular sensors for particular applications and many of them are commercially available. However, there is still a need for sensors with improved selectivity and minimum perturbation of the microenvironment to be probed. Moreover, there is the potential for progress in the development of fluorescent sensors for biochemical analytes (amino acids, coenzymes, carbohydrates, nucleosides, nucleotides, etc.). 

Many fluorescent molecular sensors for halide ions (except F ) are based on collisional quenching of a dye. In particular, the determination of chloride anions in living cells is done according to this principle. Examples of halide ion sensors are given in Figure 10.29. 

Tab. 10.4. Stern-Volmer constants (M 1) of halide molecular sensors in aqueous solutions (see chemical formulae in Figure 10.29) (data from Biwersi et al., 1994)...

In the early part of this century, many types of solid electrolyte had already been reported. High conductivity was found in a number of metal halides. One of the first applications of solid electrolytes was to measure the thermodynamic properties of solid compounds at high temperatures. Katayama (1908) and Kiukkola and Wagner (1957) made extensive measurements of free enthalpy changes of chemical reactions at higher temperatures. Similar potentiometric measurements of solid electrolyte cells are still made in the context of electrochemical sensors which are one of the most important technical applications for solid electrolytes. 

A fiber-optic device has been described that can monitor chlorinated hydrocarbons in water (Gobel et al. 1994). The sensor is based on the diffusion of chlorinated hydrocarbons into a polymeric layer surrounding a silver halide optical fiber through which is passed broad-band mid-infrared radiation. The chlorinated compounds concentrated in the polymer absorb some of the radiation that escapes the liber (evanescent wave) this technique is a variant of attenuated total reflection (ATR) spectroscopy. A LOD for chloroform was stated to be 5 mg/L (5 ppm). This sensor does not have a high degree of selectivity for chloroform over other chlorinated aliphatic hydrocarbons, but appears to be useful for continuous monitoring purposes. 

In addition to the sensors dealt with in Section 3.3.1.1, which could equally have been included in this Section as they use consumable immobilized reagents and regenerable fluorophores, Frei et al. developed a sensor for HPLC determinations based on the solid-state detection cell depicted in Fig. 3.38.B, where they immobilized 1-bromonaphthalene for measuring phosphorescence quenchers. Experiments demonstrated the sensor s usefulness for determining nitrate with a detection limit of ca. 10" M and an RSD of 4% for an analyte concentration of M. However, the scope of application of this sensor to chromatographically separated anions is rather narrow owing to the low sensitivity of the quenched phosphorescence detection for iodide and other halides [268]. 

In the method proposed by van Staden for the determination of three halides, these are separated in a short colunm packed with a strongly basic ion-exchange resin (Dowex i-X8) that is placed in an FI manifold. A laboratory-made tubular silver/silver halide ion-selective electrode is used as a potentiometric sensor. Van Staden compared the response capabilities of the halide-selective electrodes to a wide concentration range (20-5000 pg/mL) of individual and mixed halide solutions in the presence and absence of the ion-exchange column. By careful selection of appropriate concentrations of the potassixun nitrate carrier/eluent stream to satisfy the requirements of both the ion-exchange column and the halide-selective electrode, he succeeded in separating and determining chloride, bromide and iodide in mixed halide solutions with a detection limit of 5 /xg/mL [130]. 

A sensor for halides, Ch, Br and I , using fluorescence quenching of either acridinium or quinidinium-based fluorescent reagents covalently bound to a glass support via carbodiimide has been described. Other examples are sensors for Na, K+ and Ca. ... 

Polyphenylene and polyfluorene have been extensively used as fluorescence-based sensors, and several chromogenic forms of these polymers have been reported. Incorporation of monomers with additional coordination sites into these polymers has led to the development of a variety of different anion sensors, mostly for halide ions (Lee et al. 2004 Zhou et al. 2005 Vetrichelvan et al. 2006 Kim et al. 2007). Extension of these materials toward recognition of more complex analytes should be possible. 

Redox potential pH Ionic activities Inert redox electrodes (Pt, Au, glassy carbon, etc.) pH-glass electrode pH-ISFET iridium oxide pH-sensor Electrodes of the first land and M" /M(Hg) electrodes) univalent cation-sensitive glass electrode (alkali metal ions, NHJ) solid membrane ion-selective electrodes (F, halide ions, heavy metal ions) polymer membrane electrodes (F, CN", alkali metal ions, alkaline earth metal ions)... 

Chemical sensors, those that measure the presence or concentration of chemical species, are the subject of this book. Until recently, they received even less attention than other sensors in general, they are not as well developed. They have the same need to be small, inexpensive, and accurate as other sensors. However, accomplishing these requirements for chemical sensors is often more difficult than for other sensors because chemical sensors are noted for interferences. For example, a chloride sensor may be sensitive to other halides. One popular way to counter this limitation is to use an array of somewhat different sensors, each responsive to the same set of related compounds but with different sensitivity. The output of the sensor array can be processed by a computer to give greater accuracy than a single sensor for the concentration of one compound. Unfortunately, this approach tends to gain better accuracy at the expense of increased size and cost. 

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. 

---