Platinum concentrations

F1 NMR of chemisorbed hydrogen can also be used for the study of alloys. For example, in mixed Pt-Pd nanoparticles in NaY zeolite comparaison of the results of hydrogen chemisorption and F1 NMR with the formation energy of the alloy indicates that the alloy with platinum concentration of 40% has the most stable metal-metal bonds. The highest stability of the particles and a lowest reactivity of the metal surface are due to a strong alloying effect. 

Procedure To an aliquot of the sample solution containing 12.5 - 305 p.g of platinum(IV) were added 5 ml of hydrochloric acid - sodium acetate buffer of pH 2.1, 1 ml of O.IM Cu(II) sulphate solution, and 3.0 ml of 0.5% propericiazine solution. The solution was diluted to 25 ml with distilled water, mixed thoroughly, and the absorbance measured at 520 nm against a reagent blank solution after 10 min. The platinum concentration of the sample solution was determined using a standar d calibration curve. 

From results on interatomic distances derived from analysis of EXAFS data, one can draw some conclusions about the structure of platinum-iridium clusters (13,17). If the clusters were truly homogeneous, the interatomic distance characteristic of the platinum EXAFS should be identical to that characteristic of the iridium EXAFS. When we analyze EXAFS data on the clusters, however, we do not find this simple result. We find in general that the distances are not equal. The data indicate that the clusters are not homogeneous in other words,the environments about the platinum and iridium are different. We conclude that the platinum concentrates at the surface or boundary of the clusters. In the case of very highly dispersed platinum-iridium clusters on alumina, the clusters may well have "raft-like" two dimensional structures, with platinum... 

The platinum concentrations in the platinized carbon blacks are reported to be between 10 and 40% (by mass), sometimes even higher. At low concentrations the specific surface area of the platinum on carbon is as high as lOOm /g, whereas unsupported disperse platinum has surface areas not higher than 10 to 15m /g. However, at low platinum concentrations, thicker catalyst layers must be applied, which makes reactant transport to reaction sites more difficult. The degree of dispersion and catalytic activity of the platinum depend not only on its concentration on the carrier but also on the chemical or electrochemical method used to deposit it. 

Platinum is a relatively rare earth metal usually found with related metals osmium and iridium. While it has a number of industrial applications, its common consumer application is in catalytic converters. This application has actually increased platinum concentrations in roadside dust. The ability of platinum and its derivatives to kill cells or inhibit cell division was discovered in 1965. Platinum-based drugs, such as cisplatin, are used to treat ovarian and testicular cancer, and cancers of the head and neck, as well as others. Unfortunately, the toxic side effects of these agents often limit their usefulness. 

Attempts to support colloidal platinum particles with surfactant zinc porphyrin micelles allow hydrogen production at lower platinum concentrations than when the porphyrin and the particle are separate but an irreversible electron donor is still necessary for hydrogen production.116... 

Similarly, Feazell et al. tethered platinum (IV) prodrug complexes onto SWNTs through PL-PEG linkage.84 The resulting platinum (IV) complex-SWNT conjugates [SWNT-Pt (IV)] showed dramatic enhancement of cytotoxicity to Ntera-2 cancer cells, while the free platinum (IV) complex was nearly nontoxic. The cellular platinum concentration of SWNT-Pt (IV) was six times higher than that of untethered platinum (IV) complex, suggesting the effective delivery of platinum (IV) via SWNTs.84... 

For the m-cornplcxcs, a dimerization reaction to q-hydroxo species can occur (Scheme 1). Such areaction becomes significant at high platinum concentrations [20], when the pH is in the 5-7 range [24] or when the aqua species remain in solution for long periods [17]. It can be also observed with triamineaqua complexes [16]. 

Fig. 7. IC50 vs. LC50 values for HeLa cells treated with a series of platinum complexes. LC50 was determined by a colony-counting assay. /C50 was the platinum concentration at which EGFP expression was reduced to 50% of control.

Cicchella, D., De Vivo, B., and Lima, A. (2003). Palladium and platinum concentration in soils from the Napoli metropolitan area, Italy Possible effects of catalytic exhausts. Sci. Total Environ. 308 (1-3), 121-131. 

S. Rauch, H. Hemond, Sediment-based evidence of platinum concentration changes in an urban lake near Boston, Massachusetts, Environ. Sci. Technol., 37 (2003), 3283D3288. 

J. Messerschmidt, F. Alt, U. Jerono, G. Tolg, J. Angerer, K. H. Schaller, Investigations of platinum concentration within body Buids of non-exposed and occupation-ally exposed persons, 6th International Workshop of Trace Element Analytical Chemistry in Medicine and Biology, Neuherberg, 1991, pp. 24D26. 

R. Schierl, G. Fruhmann, Airborne platinum concentrations in Munich city buses, Sci. Total Environ., 182 (1996), 21D23. 

The alumina used to support the platinum in the infrared work mentioned above is composed of non-porous spheres with diameters in the 50-200 range. The supported platinum particles are approximately 5oX in diameter. The platinum concentration is 9.1 wt %. 

In addition, a two-fold molar excess of SiH groups was used in order to achieve an optimum crosslinking yield (see below). As Fig. 4 shows, the mixture achieves its final storage modulus value after 1.5 h at a reaction temperature of 30 °C with a platinum concentration of 1.5 ppm, i.e., after this time the network is fiilly formed. 

Vinyl-terminated polydimethyl siloxanes react with hydrogen silanes according to second order kinetics. The same kinetics are found in model reactions on monofunctional reactants at a lower concentration range. Also, a direct proportionality between the rate of reaction and platinum concentration is observed in both cases. Network formation does not inhibit the reaction. Polymers with lateral vinyl groups and very short chain polymers with vinyl end groups have q)proximately zero order kinetics with... 

Hutchinson, E.J., Farago, M.E., Simpson, P.R. Changes in platinum concentrations in soils and dusts from UK cities. In Zereini, F., Alt, F. (eds.) Anthropogenic platinum-group element emissions. Their impact on men and environment, pp. 57-64. Springer, Berlin (2000)... 

Probst, T.U., Rietz, B., Alfassi, Z.B. Platinum concentrations in Danish air samples determined by instrumental neutron activation analysis. J. Environ. Monit. 3, 217-219 (2001)... 

All combinations of platinum with other additives lead lo a decreased balance point temperature. The largest effect of platinum in the fuel and on the filter is observed when it is used in combination with a cerium additive. The minimum temperature is lowered with a total of 160 K. Copper and iron are more active as an individual additive, whereas the minimum temperature is higher when these additives are used, instead of cerium, in combination with the platinum additive and filter. The lowest additive concentration studied with this equipment was platinum/cerium 0.5/5 ppni/ppm. Field tests showed that the platinum concentration can be reduced to 0.25 ppm. A typical back pressure of the system at balance temperature is around 80 mbar. 

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