Cadmium-lead couple

The Troc group played an important role in Boger s synthesis of Teichopla-nin.243 Considerable effort was expended in optimising the conditions for its removal An example is the deprotection shown in Scheme 8.109. Various metals were used as reductants such as zinc, cadmium and cadmium-lead couple, but the best results (80% yield) were obtained using zinc-lead couple in M aqueous ammonium acetate in THF at room temperature. Zinc-lead couple is easily prepared. Yellow lead oxide is dissolved in warm aqueous acetic acid (1 1) and the solution added to a vigorously stirred suspension of zinc dust in deionised water. The zinc darkens as lead deposits on its surface, and forms clumps that... 

Koehler, F.M., Rossier, M., Waelle, M., Athanassiou, E.K., Limbach, L.K., Grass, R.N., Gunther, D. and Stark, W.J. (2009) Magnetic EDTA coupling heavy metal chelators to metal nanomagnets for rapid removal of cadmium, lead and copper from contaminated water. Chemical Communications, (32), 4862—4864. 

Intramolecular coupling between the aliphatic carbonyl group and a nitrile function can be achieved by reduction at a tin cathode in isopropanol. This reaction allows the formation of five- or six-membered rings only and in good yields. It has been extensively employed as a stage in the construction of condensed ring sesquiterpenes. The use of other cathode materials, cadmium, lead, or zinc, and of dime thy Iformamide as solvent resulted... 

For chemical monitoring, a list of priority substances has been established that includes metals such as cadmium, lead, and nickel. As far as metals are concerned, voltammetric techniques and more precisely electrochemical stripping analysis has long been recognized as a powerful technique in environmental samples. In particular, anodic stripping voltammetry (ASV) coupled with screen-printed electrodes (SPEs) is a great simplification in the design and operation of on site heavy metal determination in water, for reasons of cost, simplicity, speed, sensitivity, portability and simultaneous multi-analyte capabilities. The wide applications in the field for heavy metal detection were extensively reviewed (Honeychurch and Hart, 2003 Palchetti et al., 2005). 

Silva, M.M., Arruda, M.A.Z., Krug, F.J., et al. (1998). On-line separation and preconcentration of cadmium, lead and nickel in a fuUerene (Cgg) minicolumn coupled to flow injection tungsten coil atomic absorption spectrometry. Anal. Chim. Acta, 368, 255-63. 

Pozebon, D., Dressier, V. L., and Curtius, A. J. (1998). Determination of copper, cadmium, lead, bismuth and selenium(IV) in sea-water by electrothermal vaporization inductively coupled plasma mass spectrometry after on-line separation. J. Anal. At. Spectrom. 13(5), 363. 

Samples Analyzed by Inductively Coupled Plasma (ICP) Metals — Where two or more of the following analytes are requested on the same filter, an ICP analysis may be conducted. However, the Industrial Hygienist should specify the metals of interest in the event samples cannot be analyzed by the ICP method. A computer print-out of the following 13 analytes may be typically reported Antimony, Beryllium, Cadmium, Chromium, Cobalt, Copper, Iron, Lead, Manganese, Molybdenum, Nickel, Vanadium, Zinc. Arsenic — Lead, cadmium, copper, and iron can be analyzed on the same filter with arsenic. 

Contact of brass, bronze, copper or the more resistant stainless steels with the 13% Cr steels in sea-water can lead to accelerated corrosion of the latter. Galvanic contact effects on metals coupled to the austenitic types are only slight with brass, bronze and copper, but with cadmium, zinc, aluminium and magnesium alloys, insulation or protective measures are necessary to avoid serious attack on the non-ferrous material. Mild steel and the 13% chromium types are also liable to accelerated attack from contact with the chromium-nickel grades. The austenitic materials do not themselves suffer anodic attack in sea-water from contact with any of the usual materials of construction. 

Cathodic electrodeposition of microcrystalline cadmium-zinc selenide (Cdi i Zn i Se CZS) films has been reported from selenite and selenosulfate baths [125, 126]. When applied for CZS, the typical electrocrystallization process from acidic solutions involves the underpotential reduction of at least one of the metal ion species (the less noble zinc). However, the direct formation of the alloy in this manner is problematic, basically due to a large difference between the redox potentials of and Cd " couples [127]. In solutions containing both zinc and cadmium ions, Cd will deposit preferentially because of its more positive potential, thus leading to free CdSe phase. This is true even if the cations are complexed since the stability constants of cadmium and zinc with various complexants are similar. Notwithstanding, films electrodeposited from typical solutions have been used to study the molar fraction dependence of the CZS band gap energy in the light of photoelectrochemical measurements, along with considerations within the virtual crystal approximation [128]. 

The determination of lead in blood is the most widespread clinical use of ASV The technique is attractive because it is rapid, simple and reproducible A recent advance is to couple ASV to flow injection analysis in order to automate the process so that smaller samples and shorter analysis time can be achieved Lead is also routinely determined in bonemeal meant for human consumption by ASV Both lead and cadmium are determined in agricultural crops by ASV... 

Zhang Z-W, Shimbo S, Ochi N, et al. 1997. Determination of lead and cadmium in food and blood by inductively coupled plasma mass spectrometry a comparison with graphite furnace atomic absorption spectrometry. Science of the Total Environment 205(2-3) 179-187. 

Although the pyrolysis temperature can be raised up to 630 °C to reduce the nonspecific absorption (B profile), the determination of lead is a problem because the appearance temperature of lead corresponds to the maximum absorbance of the matrix signal (point X). Furthermore, the background absorbance of 1.5 A is at the limit of capability of the deuterium arc corrector. This high background, coupled with the poorer sensitivity of lead (compared to that of cadmium), limits the analytical capability of the direct determination of lead in seawater. 

Unlike halogenated solvents, it does not produce noxious substances in the inductively coupled plasma, has a very low aqueous solubility, and yields hundredfold concentration in one step. Detection limits ranged from 0.02 jtg/l (cadmium) to 0.6 pg/1 (lead). The results indicate that the proposed procedure should be useful for the precise determination of metals in oceanic water, although a higher sensitivity would be necessary for lead and cadmium. 

Berndt et al. [740] have shown that traces of bismuth, cadmium, copper, cobalt, indium, nickel, lead, thallium, and zinc could be separated from samples of seawater, mineral water, and drinking water by complexation with the ammonium salt of pyrrolidine- 1-dithiocarboxylic acid, followed by filtration through a filter covered with a layer of active carbon. Sample volumes could range from 100 ml to 10 litres. The elements were dissolved in nitric acid and then determined by atomic absorption or inductively coupled plasma optical emission spectrometry. 

Mykytiuk et al. [184] have described a stable isotope dilution sparksource mass spectrometric method for the determination of cadmium, zinc, copper, nickel, lead, uranium, and iron in seawater, and have compared results with those obtained by graphite furnace atomic absorption spectrometry and inductively coupled plasma emission spectrometry. These workers found that to achieve the required sensitivity it was necessary to preconcentrate elements in the seawater using Chelex 100 [121] followed by evaporation of the desorbed metal concentrate onto a graphite or silver electrode for isotope dilution mass spectrometry. 

Sheppard, B. S., Heitkemper, D. T., and Gaston, C. M. (1994). Microwave digestion for the determination of arsenic, cadmium and lead in seafood products by inductively coupled plasma-atomic emission and mass spectrometry. Analyst 119 1683-1686. 

It is briefly reported that the European Commission will issue a White Paper on PVC within the next couple of months. The Paper will probably be a mix of both legislation and voluntary commitments. A Green Paper on PVC was adopted by the EC in July 2000. This raised six issues to be addressed substitution, production process, cadmium stabilisers, lead stabilisers, phthalates and waste management. 

Chang, M.J., Walker, K., McDaniel, R.L. and Connell, C.T. (2005) Impaction collection and slurry sampling for the determination of arsenic, cadmium, and lead in sidestream cigarette smoke by inductively coupled plasma-mass spectrometry. Journal of Environmental Monitoring, 7(12), 1349-54. 

Coal contains several elements whose individual concentrations are generally less than 0.01%. These elements are commonly and collectively referred to as trace elements. These elements occur primarily as part of the mineral matter in coal. Hence, there is another standard test method for determination of major and minor elements in coal ash by ICP-atomic emission spectrometry, inductively coupled plasma mass spectrometry, and graphite furnace atomic absorption spectrometry (ASTM D-6357). The test methods pertain to the determination of antimony, arsenic, beryllium, cadmium, chromium, cobalt, copper, lead, manganese, molybdenum, nickel, vanadium, and zinc (as well as other trace elements) in coal ash. 

A method has been published for the determination of a variety of metals in diluted blood and serum using inductively coupled plasma atomization with mass spectrometric detection.3 Blood was diluted tenfold and serum fivefold with a solution containing ammonia, Triton X-100 surfactant, and EDTA. Detection limits adequate for measurement in blood or serum were found for cadmium, cobalt, copper, lead, rubidium, and zinc. 

Sugino 448 obtained the crossed coupling product 147 in 70% yield and current efficiency on coelectrolysis of acrylonitrile and acetone in aqueous sulfuric acid at a mercury cathode. At lead and cadmium mixed couplingwas suppressed and hydrocarbon formation increased. With methyl ethyl ketone and diethyl ketone crossed coupling was achieved in 60% and 30% yield, respectively. With acetone and maleic acid 10% terebic acid (148) was obtained. Tomilov 449- coupled acetone and acrylic acid in 95% yield (70% current efficiency) to... 

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