Cadmium selective

Crown ethers [364] have proved to be an excellent choice as ionophores for the fabrication of ion sensors because of their ability to complex selectively a particular ion. The cadmium selective sensors have been fabricated from poly(vinyl chloride) (PVC) matrix membranes containing macrocyclic ionophores benzo-15-crown-5 [365], monoaza-18-crown-6 [366], dibenzo-24-crown-8 [367], dicyclohexano-18-crown-6 [368], 3,4 ll,12-dibenzo-l,6,... 

Chow et al. have described [407] the electrochemical sensor for cadmium ions with gold electrode modified by 3-mercap-topropionic acid followed by covalently coupling the cadmium selective hexapep-tide His-Ser-Gln-Lys-Val-Phe. 

The objective of this protocol is the fabrication of a light-addressable potentiometric sensor (LAPS) for the detection of the pH value and the cadmium-ion concentration in aqueous solutions. For the pH-sensitive LAPS, use, e.g., Ta205 as a sensor membrane, and for the cadmium-selective LAPS, use a Cd2+-selective chalcogenide glass thin film as a heavy metal-sensitive material. The electrochemical sensor characterisation of the LAPS structure perform current vs. voltage (I/V) and constant current (CC) measurements. 

The first prototype of a technologically improved IWAO was developed and tested with a membrane based on a new H+-selective ketocyanine dye and a commercial cadmium ionophore [39]. Its incorporation in an IWAO allows a highly sensitive and portable optical system to be obtained for an situ chemical analysis as well. The authors propose a flow injection analysis (FIA) system for the determination of cadmium in water samples using a cadmium-selective IWAO, as an alternative method to the ones generally used in analytical control laboratories. It permits enhanced sensitive signals in short response times by taking advantage of the very thin membranes deposited over the circuit. 

Procedure Use an Inductively Coupled Plasma Atomic Emission Spectrometer (ICP-AES), or equivalent instrumentation with similar capabilities. Follow the instrument manufacturer s instructions for setting instrument parameters for assay of cadmium. Select appropriate background correction points for the cadmium analyte according to the recommendations of the instrument manufacturer. Select analytical wavelengths to yield adequate sensitivity and freedom from interference. 

Selective solution of the aluminum from the ahoy using a volatile metal, such as mercury, lead, bismuth, cadmium, magnesium, or zinc, has been investigated. After extracting the aluminum from the original ahoy into the volatile metal, the volatile metal is distilled, leaving pure aluminum. Neither electrolysis nor volatile metal extraction can extract aluminum from iron aluniinide [12004-62-3J, EeAl, titanium aluniinide [12004-78-3] TiAl, or Al C. ... 

Table 1. Physical and Chemical Properties of Selected Cadmium Compounds ...

Table 3. Thermodynamic and Stability Constant Data for Selected Aqueous Cadmium Complexes ...

Copper—cadmium and zinc—chromium oxides seem to provide most selectivity (38—42). Copper chromite catalysts are not selective. Reduction of red oil-grade oleic acid has been accompHshed in 60—70% yield and with high selectivity with Cr—Zn—Cd, Cr—Zn—Cd—Al, or Zn—Cd—A1 oxides (43). The reduction may be a homogeneously catalyzed reaction as the result of the formation of copper or cadmium soaps (44). 

Cadmium, being anodic to steel, behaves quite similarly to zinc in providing corrosion protection when apphea as a coating on steel. Tests of zinc and cadmium coatings should be conducted when it becomes necessaiy to determine the most economical selection for a particular environment. 

The quaternary ammonium salts (QAS) are widely used as ionofores of ion-selective electrodes and extractants of metals halogenic anion complexes. The influence of the QASes nature with various methyl groups contents on the cadmium extraction from bromide media has been investigated. 

Thus, the QASes of the asymmetrical stmcture with improved steric accessibility of the exchange centre show the high selectivity to double-charged cadmium bromide complex ions relative to single-charged ions. 

Some metals, such as cadmium, cobalt, and lead, are selectively car-diotoxic. They depress contractivity and slow down conduction in the cardiac-system. They may also cause morphological alterations, e.g., cobalt, which was once used to prevent excessive foam formation in beers, caused cardiomyopathy among heavy beer drinkers. Some of the metals also block ion channels in myocytes. Manganese and nickel block calcium channels, whereas barium is a strong inducer of cardiac arrhythmia. 

Cadmium is easier to solder and has a lower contact resistance than zinc, and for such reasons it may be selected for certain applications. However, account must be taken of the toxic nature of cadmium and cadmium vapour. 

Theory. Conventional anion and cation exchange resins appear to be of limited use for concentrating trace metals from saline solutions such as sea water. The introduction of chelating resins, particularly those based on iminodiacetic acid, makes it possible to concentrate trace metals from brine solutions and separate them from the major components of the solution. Thus the elements cadmium, copper, cobalt, nickel and zinc are selectively retained by the resin Chelex-100 and can be recovered subsequently for determination by atomic absorption spectrophotometry.45 To enhance the sensitivity of the AAS procedure the eluate is evaporated to dryness and the residue dissolved in 90 per cent aqueous acetone. The use of the chelating resin offers the advantage over concentration by solvent extraction that, in principle, there is no limit to the volume of sample which can be used. 

Crystalline films of 1 1 Li-Zn and Li-Cd are formed by impinging Li ions onto zinc or cadmium sheets, and heating the layer in a magnetic field set at a selected angle to form the film with a major crystallographic axis aligned with the magnetic fields... 

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