Nickel analytical determination

The application of the Chelex 100 resin separation and preconcentration, with the direct use of the resin itself as the final sample for analysis, is an extremely useful technique. The elements demonstrated to be analytically determinable from high salinity waters are cobalt, chromium, copper, iron, manganese, molybdenum, nickel, scandium, thorium, uranium, vanadium, and zinc. The determination of chromium and vanadium by this technique offers significant advantages over methods requiring aqueous final forms, in view of their poor elution reproducibility. The removal of sodium, chloride, and bromide allows the determination of elements with short and intermediate half-lives without radiochemistry, and greatly reduces the radiation dose received by personnel. This procedure was successfully applied in a study of... 

In recent years, mercury film ultramicroelectrodes have received wider application in electroanalytical practice [51,54,55]. Such electrodes are especially useful in analytical determinations, since they combine the features of ultramicroelectrodes (Chap. 12) with those of mercury film electrodes. In this case, the mercury can be deposited on carbon fibers, but many prefer a metallic support which is wetted by mercury. The solubility of the supporting metal in mercury should be low. Iridium [54] and silver [55], as well as platinum and nickel, have been used as supporting metals. Surprisingly, even gold fibers wetted by mercury have been very successfully used as electrodes in microchromatography and capillary electrophoresis detectors (Chap. 27). 

In chromium baths, ion chromatography allows the determination of the major and minor anionic components [165, 166]. Major components include chromic acid itself and sulfuric acid acting as an anionic catalyst minor components include fluoride or hexafluorosilicate, chloride, and organic acids such as methanesulfonic acid. Methanesulfonic acid is added to the bath to improve the deposition on nickel. Analytical monitoring of chromic acid plating baths is of... 

Nickel also is deterrnined by a volumetric method employing ethylenediaminetetraacetic acid as a titrant. Inductively coupled plasma (ICP) is preferred to determine very low nickel values (see Trace AND RESIDUE ANALYSIS). The classical gravimetric method employing dimethylglyoxime to precipitate nickel as a red complex is used as a precise analytical technique (122). A colorimetric method employing dimethylglyoxime also is available. The classical method of electro deposition is a commonly employed technique to separate nickel in the presence of other metals, notably copper (qv). It is also used to estabhsh caUbration criteria for the spectrophotometric methods. X-ray diffraction often is used to identify nickel in crystalline form. 

Xu Y, Liang Y. 1997. Combined nickel and phosphate modifier for lead determination in water by electrothermal atomic absorption spectrometry. Journal of Analytical Atomic Spectrometry 12(4) 471-474. 

Figure 8 shows the spectra of CO adsorbed on our samples they were taken at a CO pressure of about 1 torr. To facilitate comparison, the extinction per square meter of nickel surface, as calculated from the spectra and the analytical data of the samples, has been plotted versus the wave-number. It should be borne in mind that in the calculation of the extinction values, use has been made of the experimentally determined nickel surface areas. Hence, all inaccuracies in the surface area measurements will be reflected in the values of extinction per square meter (E/m2). 

Electrocatalysis in oxidation has apparently first been shown for ascorbic acid oxidation by Prussian blue [60] and later by nickel hexacyanoferrate [61]. More valuable for analytical applications was the discovery in the early 1990s of the oxidation of sulfite [62] and thiosulfate [18, 63] at nickel [62, 63] and also ferric, indium, and cobalt [18] hexacyanoferrates. More recently electrocatalytic activity in thiosulfate oxidation was shown also for zinc [23] hexacyanoferrate. Prussian blue-modified electrodes allowed sulfite determination in wine products [64], which is important for the wine industry. 

The results obtained by various calibrations in the determination of nickel and copper are shown in Tables 1.2 and 1.3. Table 1.4 gives the differences between sampling devices for copper, as determined by each participant, when these are significant at the 95% and 90% levels of confidence. Only the results of participants that had acceptable analytical performance, as measured by precision and agreement with contemporary consensus values for deep North Atlantic waters (Table 1.5), were used for drawing conclusions. 

Boyle and Edmond [679] determined copper, nickel, and cadmium in 100 ml of seawater by coprecipitation with cobalt pyrrolidine dithiocarba-mate and graphite atomiser atomic absorption spectrometry. Concentration ranges likely to be encountered and estimated analytical precisions (lcr) are l-6nmol/kg ( 0.1) for copper, 3-12nmol/kg ( 0.3) for nickel, and 0.0-1.1 nmol/kg ( 0.1) for cadmium. 

The nomenclature of nickel compounds should be further standardized (WHO 1991). Analytical methods must be developed and standardized in order to facilitate speciation of nickel compounds in atmospheric emissions, biological materials, and in other environmental samples (NAS 1975 WHO 1991). Studies are needed to elucidate the biogeochemical nickel cycle on a global scale and determine its potential for long-range transport (WHO 1991). 

Bruland, K. W., Franks, R. P., Knauer, G. A. and Martin, J. H. (1979). Sampling and analytical methods for the determination of copper, cadmium, zinc and nickel at the nanogram per liter level in sea water, Anal. Chim. Acta, 105, 233-245. 

Analytical Methods for Determining Nickel in Biological Samples... 

The speciation and physicochemical state of nickel is important in considering its behavior in the environment and availability to biota. For example, the nickel incorporated in some mineral lattices may be inert and have no ecological significance. Most analytical methods for nickel do not distinguish the form of nickel the total amount of nickel is reported, but the nature of the nickel compounds and whether they are adsorbed to other material is not known. This information, which is critical in determining nickel s lability and availability, is site specific. Therefore, it is impossible to predict nickel s environmental behavior on a general basis. 

Analytical methods and detection limits for nickel in biological materials are reported in Table 6-1. The presence of nickel in other biological materials such as hair and nails can be determined by the same analytical techniques used for blood and tissue after suitable procedures for dissolving the sample have been utilized (Stoeppler 1980 Takagi et al. 1986, 1988). 

Analytical methods and detection limits for standard methods of determining nickel in environmental media are reported in Table 6-2. If the determination of dissolved nickel is required, samples should be filtered with a 0.45-pm membrane filter. 

Methods for Determining Biomarkers of Exposure and Effect. Nickel concentrations in hair, nails, blood, or urine are elevated in exposed individuals. A correlation has been established between nickel levels in urine, plasma, and feces in occupationally exposed workers and nickel levels in air (Angerer and Lehnert 1990 Bemacki et al. 1978 Hassler et al. 1983). If the identity of the nickel compounds to which workers are exposed is known, nickel levels in urine and plasma can be used as a biomarker for nickel exposure (Sunderman 1993). Available analytical methods can determine the nickel levels in these media in both unexposed and occupationally exposed persons. Methods to determine nickel speciation in biological media require further development. 

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