Platinum carcinogenic potential

The most important conclusion to be made from these studies is the great importance of hydrophobicity in the modulation of the potential for mutagenicity and carcinogenicity. Hansch and coworkers have showed that compounds that require S9 activation to become mutagenic in bacteria all have log Kow terms with coefficients near 1.0 (Debnath et al., 1994). Other QSARs show that where a direct chemical reaction with DNA appears to occur, without metabolic activation, no hydrophobic term enters into the equation (Hansch et al., 2001). In these cases, usually only the electronic (reactivity) properties are important. Notable examples of QSARs based on electronic terms and without a hydrophobic term relate to the mutagenicity to Salmonella of aniloacridines, di-platinum analogs, lactones, and epoxides. All of these examples are for chemicals that do not require activation (Hansch et al., 2001). 

Nitrite Nitrite is an important indicator of fecal pollution in natural waters as well as a potential precursor of carcinogenic species. A rush of flow and sequential injection spectrophotometric method based on Griess-type reactions has been proposed, also coupled to online sorbent enrichment schemes. The catalytic effect of nitrite on the oxidation of various organic species constitutes the basis of fairly sensitive spectrophotometric methods. Fluorometric methods based on the formation of aromatic azoic acid salts, quenching of Rhodamine 6G fluorescence, and direct reaction with substituted tetramine or naphthalene species have been also reported. Indirect CL methods usually involve conversion into nitric oxide and gas-phase detection as mentioned in the foregoing section. The redox reaction between nitrite and iodide in acidic media is the fundamental of a plethora of flow injection methodologies with spectrophotometric, CL, or biamperometric detection. New electrochemical sensors with chemically modified carbon paste electrodes containing ruthenium sites, or platinum electrodes with cellulose or naphthalene films, have recently attracted special attention for amperometric detection. 

The release of VOCs into the environment has widespread environmental imph-cations. Pollution by VOCs has been linked to the increase in photochemical smog and ozone depletion. In addition, many VOCs are themselves toxic and/or carcinogenic. The US Clean Air Act of 1990 was one of the first measures to call for a 90% reduction in the emissions of 189 toxic chemicals, with 70% of these classed as VOCs, by 1998. Hence, in recent years, the development of effective technologies for the removal of VOCs from the atmosphere has increased in importance with the introduction of legislation to control their release. Various methods have been proposed, and one of the best is heterogeneous catalytic oxidation. This has the advantage over the more common original thermal oxidation process, since it requires less supplementary fuel and is therefore a less expensive process. However, the characteristics of the catalyst selected for this process are of vital importance for successful operation, and potential problems such as lifetime and deactivation must be solved if catalytic oxidation is to be employed universally. Catalysts currently in use include noble metals, notably platinum and palladium, and those based on metal oxides, however, irrespective of the type of catalyst, the most important characteristics are activity and selectivity for total oxidation. 

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