Platinum trace analysis

Rudolph, E., Hann, S., Stingeder, G., Reiter, C. Ultra-trace analysis of platinum in human tissue samples. Anal. Bioanal. Chem. 382, 1500-1506 (2005)... 

Zimmermann, S., Menzel, C.M., Berner, Z., Eckhardt, J.D., Stiiben, D., Alt, F., Messerschmidt, J., Taraschewski, H., Sures, B. Trace analysis of platinum in biological samples a comparison between sector field ICP-MS and adsorptive cathodic stripping voltammetry following different digestion procedures. Anal. Chim. Acta 439, 203-209 (2001)... 

The largest group of elements comprises those isolated from solution in the elemental form as a result of reduction, usually electrochemical. In acid solution, the electrolytic deposition of metal on a solid cathode is limited to noble and semi-noble metals. Trace analysis of copper and its compounds may serve as an example [100]. An anodic dissolution technique may be applied for the isolation of macroscopic amounts of copper. A sample in the form of a bar, plate, or wire is the anode in the electrolytic system. When current is passed through the electrolyte (nitric acid + persulphate), Cu is deposited on the graphite cathode, while most trace elements accumulate in the solution. In the trace analysis of platinum, the matrix has been also separated on a cathode [101]. 

Gold, silver, mercury, and platinum metals, as well as Se and Te, can be precipitated from acid solution in the elemental form by reduction with chemical reagents such as zinc, NH2OH, N2H4, SO2, or formic acid. In the trace analysis of high purity mercury the sample (about 100 g) is dissolved in HNO3 and the solution is warmed in the presence of formic acid. First of all, nitric acid, then mercury, is reduced. The mercury forms a separate liquid phase, and the impurities remain in the aqueous solution [102]. In the trace analysis of silver, the sample is dissolved in nitric acid, then formic acid and mercury are added. The silver liberated on reduction dissolves in the mercury to form an amalgam [102]. 

In summarizing this very brief survey, it is quite clear that ICP-MS seems to have an enormous potential in environmental trace analysis. The method is still developing therefore any final conclusions will be premature. Obviously however it is able to cover the determination of a large number of elements including very heavy elements, rare earth elements and platinum metals in a variety of environmental matrices. It is perhaps worth mentioning that when results from analysis of SRMs are presented the spectacular number of reliably determined elements decreases to 15-25 which indicates that still a lot of investigations have to be performed in order the method to occupy a realistic place among other instrumental techniques for environmental trace analysis. 

The above presentation indicates that ETAAS may be considered a powerful method in environmental trace analysis. About 25-30 elements may be determined in environmental materials, including platinum metals. CVAAS is the best method for Hg and HGAAS for the hydride-forming elements. It is however not the general practice to determine all these elements in a single study. The usual number of routinely determined elements are about ten to 12. An evidence in that respect may be found in the reports on standardization of various reference materials. Eor example in the process of standardization of IAEA SL-1 (La Brecque et al., 1987) acceptable AAS results have been reported for Ag, Ca, Cd, As, Al., Fe, Hg, Mn, Ni, Pb, Cu, Rb and Zn. 

Marczenko Z., Kasiura K., Krasiejko M. Cation-exchange separation and colorimetric determination of some elements in trace analysis of platinum-rhodium (10%) alloys. Microchimica Acta 1969 57 625-633. 

Implements for Trace Analysis of Platinum Group Metals... 

Determination of platinum- Nd YAG 266 nm Quantitative trace analysis of gold Dussubieux and Van... 

I.S. Krull, X.-D. Ding, S. Braverman, C. Selavka, F. Hochberg and L.A. Stemson, Trace analysis for ci5-platinum anti-cancer dmgs via LCEC, J. Chromatogr. Sci., 1983, 21, 166-173. 

The counter electrode consists normally of a platinum wire or a glassy carbon electrode. Either of these electrodes is suitable for trace analysis and requires no pre-treatment, unless platinum is being determined in seawater in which case a glassy carbon counter electrode should be used. 

Brummer SB, McHardy J, Turner MJ (1977) Electrical stimulation with Pt electrodes Trace analysis for dissolved platinum and other dissolved electrochemical products. Brain Behav Evol 14 10-22... 

Chemical and catalytic. This grade of platinum is for conversion to catalysts, gauzes and chemical compounds. Spectrographic analysis is employed to control the presence of trace impurities harmful in these applications. 

Podbielniak analysis See POD analysis. pad bel ne.ak a.nal a sos poison CHEM A substance that exerts inhibitive effects on catalysts, even when present only In small amounts for example, traces of sulfur or lead will poison platinum-based catalysts. poiz an )... 

Kolbe noted also the formation of traces of methyl acetate and butyl valerate from electrolysis of acetate and valerate respectively. Careful analysis of reaction products by Petersen (1900) identified compounds which are today formulated as being derived from carbocations formed by loss of one electron from the alkyl radical [50]. Propanoic acid gives mostly ethene while butanoic acid and 2-methyl-propanoic acid give mostly propene. Acetate and long chain alkylcarboxylates give mostly the Kolbe type dimer hydrocarbon on electrolysis of their potassium salts in concentrated solution at a platinum electrode, using high current density and low temperatures [51]. 

Both compounds crystallize with the cadmium diiodide structure (space group P3ml) as previously reported on polycrystalline samples.3 For platinum disulfide, ao = 3.542(1) A and c0 = 5.043(1) A, and for platinum ditelluride, a0 = 4.023(1) A and c0 = 5.220(3) A. Direct chemical analysis for the component elements was not carried out. Instead, precision density and unit-cell determinations were performed to characterize the samples. The densities of both compounds as determined by a hydrostatic technique with heptadecafluorodeca-hydro-l-(trifluoromethyl)naphthalene as the density fluid4 indicated that they are slightly deficient in platinum. For platinum disulfide, = 7.86 g/cm3 and Pmeas = 7.7(1) gm/cm3, and for platinum ditelluride, p = 10.2 gm/cm3 and Pmeas = 9.8(1) gm/cm3. In a typical experiment an emission spectrum of the platinum disulfide showed that phosphorus was present in less than 5 ppm. A mass spectroscopic examination of the platinum ditelluride revealed a small doping by sulfur (less than 0.4%) and traces of chlorine and phosphorus (less than 100 ppm). 

One of the contamination problems that was encountered illustrates the types of problems that occur in this work. A consistently high material balance was being obtained for copper. One of the platinum crucibles had been used before in the analysis of copper-containing materials. Vigorous cleaning procedures had not removed all of the copper. Now, separate virgin platinum crucibles are used for the trace work and contamination from this source has been eliminated. 

Water analysts often report trace impurities in water as "parts per million — that is, parts by weight of impurity per million parts by weight of water. In an analysis, 2.5 liters of a water sample are evaporated to a very small volume in a platinum dish the residue is treated with a sensitive reagent that develops a red color, whose intensity is a measure of the amount of nickel present. The amount of nickel present is found to be 0.41 mg. How many parts per million of nickel were present in the original sample of water (Assume that the density of water is 1 g/ml.)... 

Herr, W, and R. Wolfle A Gamma-Gamma Coincidence Arrangement for Activation-Analysis Determination of Trace Amounts of Selenium and Iridium in Minerals, Nickel, Iron and Platinum Metals. Z. Anal. Chem. 209, 213 (1965). 

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