Metals, determination spectrometry techniques

In the determination of cadmium in seawater, for both operational reasons and ease of interpretation of the results it is necessary to separate particulate material from the sample immediately after collection. The dissolved trace metal remaining will usually exist in a variety of states of complexation and possibly also of oxidation. These may respond differently in the method, except where direct analysis is possible with a technique using high-energy excitation, such that there is no discrimination between different states of the metal. The only technique of this type with sufficiently low detection limits is carbon furnace atomic absorption spectrometry, which is subject to interference effects from the large and varying content of dissolved salts. 

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... 

Spectrometric techniques based on atomic absorption or the emission of radiation flame atomic absorption spectrometry (FAAS), electrothermal atomic absorption spectrometry (ETAAS), inductively coupled plasma-optical emission spectrometry (ICP-OES), inductively coupled plasma-mass spectrometry (ICP-MS), and cold vapor (CV)/hydride generation (HG), mainly for trace and ultratrace metal determinations. 

Finally, metals (Table 12.8) are determined by UV-VIS spectrophotometry51,92-97 and atomic spectrometry techniques.50,51,98-113... 

The number of applications of atomic techniques based on solid or slurry sampling is so large that only a comparatively minute fraction is discussed in this section. Interested readers are referred to the biannual reviews of Analytical Chemistry and the atomic spectroscopy update in the Journal of Analytical Atomic Spectrometry, among other sources, for more extensive information. A specific review of the uses of graphite atomizers modified with high-melting carbides has been published by Volynsky that includes virtually all metals determined in this manner [74]. 

Hence, it is important to have test methods that can determine metals, both at trace levels and at major concentrations. Thus test methods have evolved that are used for the determination of specific metals as well as the multielement methods of determination using techniques such as atomic absorption spectrometry, inductively coupled plasma atomic emission spectrometry, and X-ray fluorescence spectroscopy. 

Relatively mild conditions are inherent to sample treatment with UV radiation. This approach has mostly been applied to metal determinations by atomic absorption/emission spectrometry and other techniques relying on torches, flames or furnaces. In spectrophotometry, it has been useful in several situations (see Table 8.1) ... 

Voellkopf, U., Paul, M. and Denoyer, E.R. (1992). Analysis of solid samples by ICP-mass spectrometry, Fres. Z. Anal. Chem. 342, 907-916 Wei, S.H.Y. (1973). Enamel microsampling technique for assessing fluoride uptake from topical fluoride treatments in vitro, J. Dent. Res. 52,1268-1272 Williams, D.M. (1979). Trace metal determinations in blood obtained in evacuated collection tubes, Clin. Chim. Acta 99, 23-29... 

Although originally FIA was conceived as a special technique for delivery of a sample segment into the instrument, the combination of flow injection as a sample pretreatment tool with atomic spectrometry has been shown to be of great potential for enhancing the selectivity and sensitivity of the measurements. Moreover, contamination problems are reduced due to the closed system used, making this interface suitable for ultratrace determination of metal species. Hyphenated techniques such as FIA/ SIA with flame atomic absorption spectrometry, inductively coupled plasma (ICP)-optical emission spectrometry, and ICP-mass spectrometry (MS) have been exploited extensively in recent years. The major attraction of FIA-ICP-MS is its exceptional multi-elemental sensitivity combined with high speed of analysis. In addition, the possibility of... 

These are among the most harmful pollutants in sewage. Essential elements (e.g., Fe) as well as toxic metals such as Cd, Hg, and Pb are included. Main sources of heavy metals are industrial wastes, mining, fuels, coal, metal plating, etc. Metal determinations in sewage are preferably carried out by atomic spectrometry (flame and electrothermal atomization), atomic emission spectrometry, inductively coupled plasma-mass spectrometry, stripping voltammetry, spectrophotometry, and kinetic methods. Hg is advantageously determined by the cold vapor technique and As by the hydride technique. 

The need for the determination of metallic constituents or impurities in pharmaceutical products has, historically, been addressed by ion chromatographic methods or various wet-bench methods (e.g. the USP heavy metals test). As the popularity of atomic spectroscopy has increased, and the equipment has become more affordable, spectroscopy-based techniques have been routinely employed to solve analytical problems in the pharmaceutical industry. Table 1 provides examples of metal determinations in pharmaceutical matrices, using spectroscopic techniques, and the reasons why these analyses are important. Flame atomic absorption spectrometry (FAAS), graphite furnace atomic absorption spectrometry... 

The solubility, or rather the total concentration, of an element in solution is an entity that is typically not too complicated to determine with techniques (e.g. mass spectrometry, inductively coupled plasma etc.) that are common tools in most laboratories. Often, the total concentration of a metal in a system is dominated by hydrolysis reactions and can be expressed as... 

Chemical analysis of the metal can serve various purposes. For the determination of the metal-alloy composition, a variety of techniques has been used. In the past, wet-chemical analysis was often employed, but the significant size of the sample needed was a primary drawback. Nondestmctive, energy-dispersive x-ray fluorescence spectrometry is often used when no high precision is needed. However, this technique only allows a surface analysis, and significant surface phenomena such as preferential enrichments and depletions, which often occur in objects having a burial history, can cause serious errors. For more precise quantitative analyses samples have to be removed from below the surface to be analyzed by means of atomic absorption (82), spectrographic techniques (78,83), etc. 

MetaUic impurities in beryUium metal were formerly determined by d-c arc emission spectrography, foUowing dissolution of the sample in sulfuric acid and calcination to the oxide (16) and this technique is stUl used to determine less common trace elements in nuclear-grade beryUium. However, the common metallic impurities are more conveniently and accurately determined by d-c plasma emission spectrometry, foUowing dissolution of the sample in a hydrochloric—nitric—hydrofluoric acid mixture. Thermal neutron activation analysis has been used to complement d-c plasma and d-c arc emission spectrometry in the analysis of nuclear-grade beryUium. 

The methods of choice for beryUium oxide in beryUium metal are inert gas fusion and fast neutron activation. In the inert gas fusion technique, the sample is fused with nickel metal in a graphite cmcible under a stream of helium or argon. BeryUium oxide is reduced, and the evolved carbon monoxide is measured by infrared absorption spectrometry. BeryUium nitride decomposes under the same fusion conditions and may be determined by measurement of the evolved nitrogen. Oxygen may also be determined by activation with 14 MeV neutrons (20). The only significant interferents in the neutron activation technique are fluorine and boron, which are seldom encountered in beryUium metal samples. 

Surface analysis has made enormous contributions to the field of adhesion science. It enabled investigators to probe fundamental aspects of adhesion such as the composition of anodic oxides on metals, the surface composition of polymers that have been pretreated by etching, the nature of reactions occurring at the interface between a primer and a substrate or between a primer and an adhesive, and the orientation of molecules adsorbed onto substrates. Surface analysis has also enabled adhesion scientists to determine the mechanisms responsible for failure of adhesive bonds, especially after exposure to aggressive environments. The objective of this chapter is to review the principals of surface analysis techniques including attenuated total reflection (ATR) and reflection-absorption (RAIR) infrared spectroscopy. X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), and secondary ion mass spectrometry (SIMS) and to present examples of the application of each technique to important problems in adhesion science. 

As was suggested in the preceding discussion, most of the arene complexes isolated by metal-atom techniques are benzene derivatives. However, heterocyclic ligands are also known to act as 5- or 6-electron donors in transition-metal 7r-complexes (79), and it has proved possible to isolate heterocyclic complexes via the metal-atom route. Bis(2,6-di-methylpyridine)Cr(O) was prepared by cocondensation of Cr atoms with the ligand at 77 K (79). The red-brown product was isolated in only 2% yield the stoichiometry was confirmed by mass spectrometry, and the structure determined by X-ray crystal-structure analysis, which supported a sandwich formulation. 

HPLC (in both NP and RP modes) is quite suitable for speciation by coupling to FAAS, ETAAS, ICP-MS and MIP-MS [571,572]. Coupling of plasma source mass spectrometry with chromatographic techniques offers selective detection with excellent sensitivity. For HPLC-ICP-MS detection limits are in the sub-ng to pg range [36]. Metal ion determination and speciation by LC have been reviewed [573,574] with particular regard to ion chromatography [575]. 

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