Copper species speciation/metals

If an aqueous sample is shaken with a volume of immiscible organic solvent, uncharged species tend to be extracted into the organic layer. This liquid-liquid extraction procedure has some applications in speciation studies. For example, organically associated copper species have been isolated by extracting water samples with chloroform, carbon tetrachloride (Slowey et al., 1967) or hexane. The lipid-soluble fraction of copper and other metals has been extracted from natural waters using solvent mixtures such as w-hexane, 10% butanol and w-octanol and 20% butanol in hexane (Stiff, 1971 Florence, 1982). The liquid-liquid extraction efficiencies are possibly low, due to... 

A procedure is developed through which the relative toxicity of metal speciation products can be determined. The procedure is illustrated utilizing data from a published study on the toxicity of copper to VaphyuxL magna and tentative conclusions are drawn with respect to the relative toxicity of certain combinations of species. The experiments necessary to obtain a better description of the relative toxicity of copper species to toxicity are described. 

Numerous and disparate copper criteria are proposed for protecting the health of agricultural crops, aquatic life, terrestrial invertebrates, poultry, laboratory white rats, and humans (Table 3.8) however, no copper criteria are now available for protection of avian and mammalian wildlife, and this needs to be rectified. Several of the proposed criteria do not adequately protect sensitive species of plants and animals and need to be reexamined. Other research areas that merit additional effort include biomarkers of early copper stress copper interactions with interrelated trace elements in cases of deficiency and excess copper status effects on disease resistance, cancer, mutagenicity, and birth defects mechanisms of copper tolerance or acclimatization and chemical speciation of copper, including measurement of flux rates of ionic copper from metallic copper. 

Due to the various health risks of different element species, there are a multitude of applications for natural water samples in this field (e.g., Cr and Sb speciation or Br and I determination).19 The investigation of heavy metal complexes with humic substances by isotope dilution SEC-ICP-MS has been described, for example, by McSheehy and Mester.20 Copper, zinc and molybdenum were found to form complexes with similar size fractions of humic substances in seepage water samples from soils. Sturgeon s group proposed the use of solid phase microextraction (SPME)... 

Florence, T.M. (1977) Trace metal species in fresh waters. Water Res., 11, 681-687. Florence, T.M. (1982) Development of physicochemical speciation procedures to investigate the toxicity of copper, lead, cadmium and zinc towards aquatic biota. Anal. Chim. Acta, 141, 73-94. 

Examples showing that metal speciation is important to metal toxicity include arsenic, copper, selenium, and chromium. While ionic copper (Cu2+) and CuClj are highly toxic, Q1CO3 and Cu-EDTA have low toxicity (Morrison et al, 1989). Toxicity tests show that As(III) is about 50 times more toxic than As(VI). Trivalent chromium is much less toxic than hexavalent chromium, probably because Cr(VI) is much smaller and the chemical structure of chromate is similar to sulfate. A special channel already exists in biomembranes for sulfate transport. While modeling metal speciation is not always possible, and redox equilibrium is not achieved in all natural waters, geochemical modeling of equilibrium species distribution remains one of the methods of discerning metal speciation. 

In aquatic environments, more research is needed on the chemical speciation of silver to evaluate risk to the organism and its consumers. Most silver criteria formulated for the protection of aquatic life are now expressed as total recoverable silver per liter. But total silver measurements do not provide an accurate assessment of potential hazard. Silver ion (Ag+), for example, is probably the most toxic of all silver chemical species and must be accurately measured in the assessment of silver risks in aquatic environments, perhaps as acid-soluble silver. Little is known of the biocidal properties of Ag + andAg + that are the active ingredients in disinfectants and used increasingly in water purification systems of drinking water and swimming pools. The effects of these silver species on organism health clearly must be researched. Silver interactions with other metals and compounds in solution are not well defined. For example, mixtures of salts of silver and copper markedly increased the survival of oyster embryos, but only when... 

The preconcentration techniques described in this review have been or can be applied with some modification to all of the priority pollution metals. Applications to mercury, lead, copper, chromium, and nickel abound in the literature, whereas relatively few refer to the concentrating of beryllium, thallium, and selenium. Despite the growing need to determine the particular metal species in solution, very few authors have outlined the actual species concentrated and the separation factors involved. The area of speciation should continue to grow rapidly as more methods of selectively concentrating particular species become available. In particular, ion exchange and other sorption methods will play an important role. 

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