Determinations metals

Luce T A and Bennemann K H 1998 Nonlinear optical response of noble metals determined from first-principles electronic structures and wave functions calculation of transition matrix elements P/rys. Rev. B 58 15 821-6... 

Table. Extraction-spectrophotometric methods of metals determination...

DIBROMO-PADAPH AS THE REAGENT FOR PLATINUM METALS DETERMINATION... 

The most universal method for sample destmction before SPh metal determination (Ee, Mo, A1 and etc.) is the sulfur acid digestion at high temperature by Kjeldall. It can be enforced by microwave decomposition in the microwave oven. 

The results of the complexation study of Cu(II), Pb(II), Zn(II), Fe(III), Hg(II), Cd(II), Sn(IV), Zr(IV), Ti(IV) with arsenazo III, sulfonazo III, SPADNS, Eriochrome T, Acid Chrome Dai k Blue, Xylenol Orange, Methyl Thymol Blue, Pyrocatechol Violet, Chrome Azurol S, Eriochrome Cyanin R, Basic Blue K, Methyl Violet, Brilliant Green, Rhodamine C and Astraphoxin in solid phase. The obtained data ai e used for the working out of a new method of metal determination. 

This chapter introduces the generic metals. But rather than bore you with a catalogue we introduce them through three real engineering examples. They allow us not only to find examples of the uses of the main generic metals but also to introduce the all-important business of how the characteristics of each metal determine how it is used in practice. 

Exfoliation corrosion is especially prevalent in aluminum alloys. The grain structure of the metal determines whether exfoliation corrosion will occur. In this form of corrosion, degradation propagates below the surface of the metal. Corrosion products in layers below the metal surface cause flaking of the metal. 

In the search for new fluorometric reagents for trace metal determinations, ferroin-type compounds, namely 2-(2-pyridyl)-2//- and 2-(3-isoquinolyl)-3//-imidazo[4,5-/i]quinolines, and their silver, lead, and zinc chelates were tested for luminiscence in aqueous ethanol solutions at various pH values (80TAL1021). 

Otto, M. et. al. "Spectrophotometric Multicomponent Analysis Applied to Trace Metal Determinations", Anal. Chem. 1985 (57) 63-69. 

It must be noted that there are a number of more or less arbitrary assumptions made in this work30,31 which need justification, as well as parameters whose values should be calculated rather than assumed. For instance, the importance of the distance dl9 taken as equal to Rc, has been mentioned. In principle, the value of this distance is a consequence of the forces between components of the metal and molecules of solvent, and would be calculated in a consistent model of the complete interface. This was pointed out by Yeager,18 who noted that the electron density tail of the metal determines the distance of closest approach of solvent in the interface, as well as the behavior of the solvent dipoles on the surface. Since changing qM will move the electron density tail in and out, dx should depend on the state of charge of the interface. In fact, it turns out31 that if dx varies linearly with surface charge according to... 

It was generally agreed that any determinations of trace metals carried out on seawater prior to about 1975 are questionable, principally due to the adverse effects of contamination during sampling, which were then little understood and lead to artificially high results. It is only in the past few years that methods of adequate sensitivity have become available for true ultra-trace metal determinations in water. 

Mart [86] has described typical sample bottle cleaning routine for use when taking samples for very low level metal determinations. 

Maximum power heating, the L vov platform, gas stop, the smallest possible temperature step between thermal pretreatment and atomisation, peak area integration, and matrix modification have been applied in order to eliminate or at least reduce interferences in graphite furnace AAS. With Zeeman effect background correction, much better correction is achieved, making method development and trace metal determinations in samples containing high salt concentrations much simpler or even possible at all. 

Bond et al. [791 ] studied strategies for trace metal determination in seawater by ASV using a computerised multi-time domain measurement method. A microcomputer-based system allowed the reliability of the determination of trace amounts of metals to be estimated. Peak height, width, and potential were measured as a function of time and concentration to construct the database. Measurements were made with a potentiostat polarographic analyser connected to the microcomputer and a hanging drop mercury electrode. The presence of surfactants, which presented a matrix problem, was detected via time domain dependent results and nonlinearity of the calibration. A decision to pretreat the samples could then be made. In the presence of surfactants, neither a direct calibration mode nor a linear standard addition method yielded precise data. Alternative ways to eliminate the interferences based either on theoretical considerations or destruction of the matrix needed to be considered. 

Holzbecker and Ryan [825] determined these elements in seawater by neutron activation analysis after coprecipitation with lead phosphate. Lead phosphate gives no intense activities on irradiation, so it is a suitable matrix for trace metal determinations by neutron activation analysis. Precipitation of lead phosphate also brings down quantitatively the insoluble phosphates of silver (I), cadmium (II), chromium (III), copper (II), manganese (II), thorium (IV), uranium (VI), and zirconium (IV). Detection limits for each of these are given, and thorium and uranium determinations are described in detail. Gamma activity from 204Pb makes a useful internal standard to correct for geometry differences between samples, which for the lowest detection limits are counted close to the detector. 

This picture of chemisorbed atoms on jellium, although much too simple, illustrates a few important aspects of chemisorption. First, the electron levels of adsorbed atoms broaden due to the interaction with the s-electron band of the metal. This is generally the case in chemisorption. Second, the relative position of the broadened adsorbate levels with respect to the Fermi level of the substrate metal determines whether charge transfer between metal and adatom takes place and in which direction. 

In an interlaboratory comparison of metal determinations in soils the element boron is mentioned [7]. 

Lynch et al. [21] have described a method for the determination of organic carbon in silty lake sediments. In this method the air-dried and sifted (-250 mesh) sample is leached with 4M nitric acid-0.1M hydrochloric acid for 1.5h at 90-95°C, and the extinction of the cooled, clean solution is measured at 500nm. The extinction correlates well with weight loss (%) on heating the sample between 120 and 800°C. The precision is 26%. The same leach solution can be used for trace-metal determinations. 

Note if determinations of certain volatile elements such as mercury or selenium are required it is necessary to carry out these analyses on the wet sample as received (to avoid loss of element by drying at 105°C). The dry weight of material in the sample is obtained by determining moisture in a separate position of the sample and applying a correction to the sample weight used in metals determination. 

Titrations consist of the observation of one or several measures as a function of the addition of an appropriate reagent. Reagents are typically acids or bases or ligands in metal determinations. Measurements are typically pH and/or absorption spectra. We concentrate on the data analysis of these two types. It should be straightforward for the reader to adapt the algorithms to other observations. Currently, most titrations are done under computer control, either by commercial auto-titrators or by assemblies of burettes, sensors and vessels in the research laboratories. This is not crucial and the analysis of such a titration is essentially identical with the analysis of a manual titration. 

Ion exchanger colorimetry has been used as a sensitive and rapid method for vanadium analysis by immobilization of 2[2-(3-5-dibromopyri-dyl)azo]-5-dimethylaminobenzoic acid onto an ion exchanger resin AG 1X2 [75]. Solid phase fluorimetry can be useful for the analysis of very dilute solutions in water analysis or trace metal determination thus a chelating 8-(benzene-sulfonamido)quinoline, immobilized on Amberlite XAD2 support, has been used for the spectrofluorimetric determination of Zn(II) and Cd(II) [76]. 

Other applications of supported liquid membranes have been related to metal speciation. For example, recently a system for chromium speciation has been developed based on the selective extraction and enrichment of anionic Cr(VI) and cationic Cr(III) species in two SLM units connected in series. Aliquat 336 and DEHPA were used respectively as carriers for the two species and graphite furnace atomic absorption spectrometry used for final metal determination. With this process, it was possible to determine chromium in its different oxidation states [103]. 

Ottaway, J. M. Heavy metals determinations by atomic absorption and emission spectrometry in Analytical Techniques for Heavy Metals in Biological Fluids, (ed.) Facchetti, S., Amsterdam—Oxford—New York Elsevier 1983... 

Metallic biomaterials (metals such as Ti or its alloys and others) are used for the manufacture of orthopaedic implants due to their excellent biocompatibility with respect to electrical and thermal conductivity and their mechanical properties, e.g., for hard tissue replacement such as total hip and knee joints, for fracture healing aids such as bone plates and screws or dental implants. For example, Co-Cr-Mo alloys are employed for metal-on-metal hip bearings in total joint replacements. Problems with implants occur because of ion release in patients with metal implants. To control this ion release, the ultratrace determination of Co, Cr and Mo in the blood (or serum) and urine of patients with Co-Cr-Mo alloy hip implants is carried out routinely in the author s laboratory. The trace metal determination of Co, Cr and Mo in complex matrices such as urine and blood by ICP-MS is not trivial due to the low concentrations expected in the sub-ngmF1 range, the possible danger of contamination during sample collection, sample preparation and the... 

---