Ultratrace constituents

The constituents determined in an analytical procedure can cover a huge range in concentration. In some cases, analytical methods are used to determine major constituents. These constituents are present in the relative weight range of 1% to 100%. Many of the gravimetric and some of the volumetric procedures discussed in Part III are examples of major constituent determinations. As shown in Figure 8-2, species present in the range of 0.01% to 1% are usually termed minor constituents, whereas those present in amounts between 100 ppm (0.01%) and 1 ppb are termed trace constituents. Components present in amounts less than 1 ppb are usually considered to be ultratrace constituents. 

Determination of Hg in the ppb to pspm range in a 1-p.L ( I mg) sample of river water would be a micro analysis of a trace constituent. Determinations of trace and ultratrace constituents are particularly demanding because of potential interferences and contaminations. In extreme cases, determinations must be per-... 

Suitable for ultratrace contents through to major constituents... 

For many methods of elemental analysis, the organic constituents of plant material are eliminated either by dry ashing or by wet digestion (Sulcek and Povondra, 1989). Stoeppler (1991) has summarised the most frequently used decomposition methods for trace and ultratrace analysis of biological and environmental materials. 

Mass spectrometry (MS) is being used increasingly as an analytical tool to solve complex problems in biochemistry and medicine. As a matter of fact, there are five ways that mass spectrometry can be applied to problems in these areas (Roboz, 1975) (1) confirmation of identity, (2) identification of unknowns, (3) elucidation of the structure of complex molecules, (4) quantitation of selected constituents present in ultratrace quantities, and (5) dynamic analysis of major constituents in vivo. 

Minerals The main mineral constituents in milk are calcium and chlorine, magnesium chloride, phosphate, and citrate. Minerals in milk are mainly present as soluble salts or in colloidal form associated with caseins. Their concentrations may vary enormously. Thus, the minerals present in milk can be classified according to their concentration level as major and minor elements, with small quantitative contributions from trace and ultratrace elements. The total content of minerals in mammalian milks should correspond to the growth requirements of each biological species. Accordingly, the mineral total content in cow milk is four times higher than in human milk. 

Role of Copper in the Enzyme System. It is now well recognized among workers in the ultratrace-metal field that copper is an essential nutrient for all forms of life, being the vital constituent of all living cells (32), The essentiality of copper is by virtue of its ability to catalyze biological oxidation whether the copper is in the protein-boimd or ionic form, although it is likely that the ionic copper is able to do this more eflBciently than the protein-bound copper (33),... 

Tellurium is used in the metallurgical industry as an alloy constituent. Tellurium improves the acid resistance of lead used in batteries. It is also used in the manufacture of heat- and abrasive-resistant rubber. Tellurium is obtained as a by-product in the electrolytic refining of copper. In the semiconductor industry, the ultratrace level determination of tellurium in tellurium-doped single crystals is often required. Tellurium species are highly toxic. 

Environmental and agricultural studies involve a number of different materials that need to be analysed. The principal test materials encountered by the analyst in this sector are soils, sediments, air, dusts, water, plant material and animal tissue. For completely practical reasons, we need to know the composition of these media over wide concentration ranges, from major constituents to elements at ultratrace levels. One is especially interested in the way elements are transferred between media, their biological role and metabolic pathways, and their ultimate fate. 

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