Chloride sensors

Huber C., Werner T., Krause C., Wolfbeis O.S., Leiner M.J.P., Overcoming the pH-Dependency of Optical Sensors a pH-Independent Chloride Sensor Based on Co-Extraction, Anal. Chim. Acta 1999, 398 137. 

Ceresa A, Qin Y, Peper S, Bakker E (2003) Mechanistic insights into the development of optical chloride sensors based on the [9]mercuracarborand-3 ionophore. Anal Chem 75 133-140... 

If the oxygen sensitive dye is replaced by a pH sensitive dye, optical pH sensors can be produced. Thus miniaturization of these sensors is easy, and multisensing systems can be set up. Different sensor types for biotechnical application are described in the literature (e.g., ethanol and chloride sensors) [23,24]. 

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. 

Urushi, a natural lacquer, has been used on the ISFET surface [89] to make, amongst other devices, a chloride sensor. The natural lacquer has a long curing time (10 days) but this can be shortened to 2-3 days with the use of formaldehyde as a crosslinking agent [90] and has been successfully used in the production of a nitrate sensor. 

Sol-gel methods have been used to form membranes on sensor surfaces by the mixing of the ion-sensitive molecule with alkoxysilanes which then crosslink to form a hard, transparent coating on the sensor. For example, tridodecyl-methylammonium chloride-doped films were used as a chloride sensor and showed Hofmeister-type selectivity [91]. Long cure times (several days), however, represent a disadvantage in this process [91]. 

Sodium, potassium and chloride sensors were evaluated using undiluted serum specimens with no sample pretreatment of any kind. The performance data set, summarized by Table II, comprises a minimum of 8 sensors and 60 samples. The bicarbonate assays were performed separately on serum specimens buffered at pH 9.0. Clinical efficacy is normally judged by the response linearity, precision and... 

Figure 16.15 Structures of Ru(bpy)3-based fluorescent chloride sensors...

Chloride content. By embedding the combined chloride/resistivity sensor elements mentioned above (Figure 17-2), the activity of the free chloride ions in the pore solution of concrete can be monitored over time at different depths. The potential of the embedded chloride sensors is measured versus a Mn02 reference electrode and converted by Nernst s law to chloride concentration. In several field applications, hundreds of chloride sensors worked well over several years [15]. A more detailed description of the chloride sensor, its calibration and long-term stability is given in references [20,22]. 

A major concern in this study was localization of the tip of the double-barreled microelectrode (Fig. 1) in the intracellular compartment of proximal tubular cells. The reference barrel is the electrical sensor the other barrel being the chemical (potassium or chloride) sensor. The leads of the two barrels were connected to one electrometer and this gave the ionic potential. The leads of the reference barrel and an external 3 M NaCl single pipette were connected to another electrometer and the PD between them represented the membrane potential. The ionic potential (K or Cl") and the... 

These host mercuracarborand molecules were applied in Ion Selective Electrodes (ISE) and membrane formulations, as selective optical chloride sensors, as sensitive liquid/polymeric membrane electrodes for anions and as catalysts. ... 

A disadvantage of all three designs was that the detection of chloride is irreversible—the silver chloride does not revert back to either silver nitrate or silver chromate when the concentration of chloride ions decreases. It has been suggested that a reversible chloride sensor may be based on the absorption peak at 0.360 xm for salt water. 

Cosentino, R, Grossman, B., Shieh, C., et al., Fiber-Optic Chloride Sensor Development, Journal of Geotechnical Engineering, 121(8) 610-617 (1995). 

These days, the use of a pH glass indicator electrode and an Ag/AgCl reference electrode along with a high-resistance electrometer is not common practice. Instead, a combined pH/silver-silver chloride sensor shown in Eigure 5.4 is conunonly used... 

FIGURE 5.4 Schematic of a combined pH/silver-silver chloride sensor. (1) Ag/AgCl reference electrode, (2) salt bridge, (3) filling hole, (4) reference electrode solution, (5) internal buffer solution, (6) Ag/AgCl internal electrode, (7) pH-sensitive glass membrane, and (8) Pt wires. 

FIGURE 5.5 Schematic of a system for measuring pFf (1) test solution, (2) combined pH glass/silver-silver chloride sensor (see Figure 5.4), and (3) magnetic stirrer. 

Gallardo J, Alegret S, Valle MD (2004) A flow-injection electronic tongue based on poten-tiometric sensors for the determination of nitrate in the presence of chloride. Sensors Actuators B 101 72-80... 

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