Platinum origin

Table 11 summarizes results of spin trapping experiments where PBN-Nu and other ST-Nu" systems have been oxidized anodically at platinum. Originally, all the reactions were suggested to proceed via Nu radicals (Janzen et al., 1980 Walter et al., 1982), but the fact that PBN is oxidized at a lower potential than Cl-, CNO and CN- (Tables 1 and 5) clearly shows that the faster electrochemical process must be PBN— PBN + at the potentials employed. On the other hand, azide ion is oxidized in a faster reaction than any of the spin traps used and thus azide radical is implicated as being trapped. The Cr 4MePyPBN [17] system is a case where possibly Cl is involved in view of the high pa of this spin trap. 

ICP-MS has been employed, as discussed in Section 9.5, for the determination of platinum originating from cisplatin, carboplatin and oxaliplatin in human plasma ultrafiltrate. The method developed was successfully used to support pharmacokinetic studies in cancer patients treated with cisplatin, carboplatin or oxaliplatin.5 Counterfeit products on the drug market, which have important implications for pharmaceutical companies and human health, can be clarified by mass spectrometric isotope ratio measurements. For example, precise and accurate sulfur isotope measurements (a 54S) by MC-ICP-MS, were employed to study the isotope variation of pharmaceuticals and to detect to the origin of counterfeits by Clough el al.6... 

Brouwers, E.E.M., Tibben, M.M., Rosing, H., Hillebrand, M.J.X., Joerger, M., Schellens, J. H.M., Beijnen, J.H. Sensitive inductively coupled plasma mass spectrometry assay for the determination of platinum originating from cisplatin, carboplatin, and oxaliplatin in human plasma ultrafiltrate. J. Mass Spectrom. 41, 1186-1194 (2006)... 

Fraction (A) of O2 Gas Produced in the Decomposition of Hydrogen Peroxide on Platinized Platinum Originating from Two Different Peroxide Molecules Rather than Just a Single Peroxide Moiecuie ... 

A. C. da Costa Junior, M. A. Vieira, A. S. Luna and R. C. de Campos, Determination of platinum originated from antitumoral drugs in human urine by atomic absorption spectrometric methods, Talanta, 2010, 82, 1647-1653. 

Experimentally, the aqueous iron(II) is titrated with cerium(IV) in aqueous solution in a burette. The arrangement is shown in Figure 4.6, the platinum indicator electrode changes its potential (with reference to a calomel half-cell as standard) as the solution is titrated. Figure 4.7 shows the graph of the cell e.m.f. against added cerium(IV). At the equivalence point the amount of the added Ce (aq) is equal to the original amount of Fe (aq) hence the amounts of Ce (aq) and Fe (aq) are also equal. Under these conditions the potential of the electrode in the mixture is ( - - f)/2 this, the equivalence point, occurs at the point indicated. 

These elements formed Group IIB of Mendeleef s original periodic table. As we have seen in Chapter 13, zinc does not show very marked transition-metaf characteristics. The other two elements in this group, cadmium and mercury, lie at the ends of the second and third transition series (Y-Cd, La-Hg) and, although they resemble zinc in some respects in showing a predominantly - - 2 oxidation state, they also show rather more transition-metal characteristics. Additionally, mercury has characteristics, some of which relate it quite closely to its immediate predecessors in the third transition series, platinum and gold, and some of which are decidedly peculiar to mercury. 

Quantitative estimation of cyclohexane in the presence of benzene and aUphatic hydrocarbons may be accompHshed by a nitration-dehydrogenation method described in Reference 61. The mixture is nitrated with mixed acid and under conditions that induce formation of the soluble mononitroaromatic derivative. The original mixture of hydrocarbons then is dehydrogenated over a platinum catalyst and is nitrated again. The mononitro compounds of the original benzene and the benzene formed by dehydrogenation of the cyclohexane dissolve in the mixed acid. The aUphatic compound remains unattacked and undissolved. This reaction may be carried out on a micro scale. 

During regeneration the coke is burned off the catalyst. The techniques employed are fairly sophisticated so as to maintain the platinum and any other active metals ia a well dispersed form and to restore the original catalyst activity. Regeneration usually takes several days. 

Contact process for SO3/H2SO4 patented by P. Philips of Bristol, UK (tlie original platinum catalyst was. subsequently replaced by ones ba.sed on V2O5). 

The parent system 3 was reported fw the first time as a product obtained in low yield originating from the vapor-phase cyclodehydrogenaticMi of /V,/V -diphenyl-m-phenylenediamine (137) over a platinum-on-magnesium catalyst (Scheme 17) (61JOC1509). 

Methylcyclopentane-l,3-dione has been prepared in 15% yield by the catalytic reduction of 2-mcthylcyclopentane-l,3,5-trione over platinum.2 The present method is based on the original procedure 3 of Panouse and Sannie with improvements as effected by Boyce and Whitehurst4 and the submitters.6... 

No. 41 or 541 filter paper. Wash the precipitate first with warm, dilute hydrochloric acid (approx. 0.5M), and then with hot water until free from chlorides. Pour the filtrate and washings into the original dish, evaporate to dryness on the steam bath, and heat in an air oven at 100-110 °C for 1 hour. Moisten the residue with 5 mL concentrated hydrochloric acid, add 75 mL water, warm to extract soluble salts, and filter through a fresh, but smaller, filter paper. Wash with warm dilute hydrochloric acid (approx. 0.1M), and finally with a little hot water. Fold up the moist filters, and place them in a weighed platinum crucible. Dry the paper with a small flame, char the paper, and burn off the carbon over a low flame take care that none of the fine powder is blown away. When all the carbon has been oxidised, cover the crucible, and heat for an hour at the full temperature of a Meker-type burner in order to complete the dehydration. Allow to cool in a desiccator, and weigh. Repeat the ignition, etc., until the weight is constant. 

The original blue (K.A. Hofmann, 1908) was obtained from the reaction of Pt(MeCN)2Cl2 with silver salts over some hours. Under these conditions, the nitrite is hydrolysed to acetamide. Very recently, the structure of the complex [(H3N)2Pt(MeCONH)2Pt(NH3)2]4(NO3)10 has been determined (Figure 3.37). The average oxidation state of the platinums in the octamer is 2.25. 

Characteristic x-ray emission spectra, from x-ray excitation, 27, 28 of platinum, measurement by Bragg, 25, 26, 35 origin, 30-34... 

Recently it was demonstrated that a platinum black-PTFE electrode, originally designed for a fuel cell, is excellent for the chlorination of double bonds and, depending on the other electrolysis conditions, it was possible to isolate the dichlorocompound or the chlorohydrin (Danger and Yurchak, 1970). Moreover, if a chlorine cathode is used, the overall process occurs with a net output of energy, i.e. the cell may do external work and the procedure has been named electrogenerative chlorination . 

Most frequently platinum is used as electronically conducting phase of the hydrogen electrode, thus it is mentioned only when explicitly stated also in the original report. 

The addition of various Kolbe radicals generated from acetic acid, monochloro-acetic acid, trichloroacetic acid, oxalic acid, methyl adipate and methyl glutarate to acceptors such as ethylene, propylene, fluoroolefins and dimethyl maleate is reported in ref. [213]. Also the influence of reaction conditions (current density, olefin-type, olefin concentration) on the product yield and product ratios is individually discussed therein. The mechanism of the addition to ethylene is deduced from the results of adsorption and rotating ring disc studies. The findings demonstrate that the Kolbe radicals react in the surface layer with adsorbed ethylene [229]. In the oxidation of acetate in the presence of 1-octene at platinum and graphite anodes, products that originate from intermediate radicals and cations are observed [230]. 

---