Speciation chemistry

Speciation (chemistry) The chemical species in a sample, which includes information on its valence state and specific chemistry. For example, the speciation of arsenic in a groundwater sample may include arsenic fluoride species, such as AsCbF2-. Also, an analytical method that identifies the valence state of a chemical species in a sample. 

Includes bibliographical references and index. ISBN 0-632-05848-X 1. Speciation (Chemistry) 2. Chemistry, Analytic. 3. Environmental chemistry. I. Ure, A. M. II. Davidson, C. M. 

Another key factor in the popularity of the technique is its increasingly widespread use in speciation chemistry. The current awareness of the importance of the chemical form in which an element is present in food (e.g., the oxidation state, the nature of the ligands, and the molecular structure), on its possible absorption and fate inside the body, has made elemental speciation a prominent topic of present research in the food science. If speciation critically influences the bioavailability, essentiality, or toxicity of an element, the analytical techniques that enable species discrimination and quantification gather prominence. ICP-MS has the capability for quantifying metal (metalloid)-containing species in a chromatographic or capillary electrophoresis effluent or, as recently demonstrated, in a gel spot after SDS-PAGE via electrothermal vaporization (ETV) or laser ablation (LA) [4, 5]. Hence, it has firmly established as a sensitive,... 

TABLE 10.4 Silica Speciation Chemistry and Solubility (logioK) ... 

This chapter will review information relevant to the biogeochemical cycle of mercury, specifically (i) the speciation chemistry of mercury, (ii) the fate of mercury in air, water and sediment, and (iii) the effects of landscape changes on mercury fate. The chapter will end with a summary of a recent multidisciplinary mercury mass balance conducted in Kejimkujik Park (Nova Scotia, Canada). 

Recent work has investigated the possibilities of modelling the speciation chemistry of actinides in wound fluids (Lunn 1990). This theoretical work supports the views expressed above that the initial physicochemical form determines the rate of mobilisation from the wound site. Thus, oxides are dissolved in wound fluids to a negligible extent even in the presence of strong chelators such as diethylenetriaminepentaacetate (DTPA). This may have important implications with respect to treatment of wound-contamination incidents where surgical excision is often combined with chelation therapy and wound washing with DTP A (Carbaugh et al. 1989). 

As of the mid-1990s, soluble sihcates are used primarily as sources of reactive siUca (57%), in detergency (qv) (23%), in pulp (qv) and paper (qv) production (7%), for adhesives and binders (5%), and in other appHcations (8%). The stmcture and chemistry of solutions containing polymeric siHcate species have been characterized using modem analytical techniques. This improved understanding of siHcate speciation contributes to the development of new markets. Thus, the sodium silicates constitute a versatile, stable, and growing commodity and are ranked among the top 50 commodity chemicals. 

Prediction of the chemistry of plutonium in near-neutral aqueous media is highly dependent on understanding reactions that may be occurring in such media. One of the most important parameters is the stability and nature of complexes formed by plutonium in its four common oxidation states. Because Pu(III), Pu(IV), and Pu(VI) are readily hydrolysed, complexation reactions generally are studied in mildly to strongly acidic media. Data determined in acid media (and frequently at high concentrations of plutonium) then are used to predict the chemical speciation of plutonium at near-neutral pH and low concentrations of the metal ion. 

The chemistry of waste treatment processes and the development of new processes are fertile areas of research work. The speciation of plutonium in basic and laundry wastes is needed. For example, if soluble plutonium complexes in basic wastes can be destroyed, perhaps ultrafiltration could replace the flocculent-carrier precipitation process. The chemistry of plutonium(VII) and of ferrites—a candidate waste treatment process—needs to be explored.(23)... 

Capodaglio, G., Scarponi, G., K.H. Coole, K.W. Bruland. Lead Speciation in surface seawaters. X Int. Symp. Chemistry of the Mediterranean, Primosten, Yugoslavia, 4-12 May 1988. 

Andreae, M. O. (1979). Arsenic speciation in seawater and interstitial waters the role of biological-chemical interactions on the chemistry of a trace element. Limnol. Oceanog. 24,440-452. 

Vol. 135. Element Speciation in Bioinorganic Chemistry. Edited by Sergio Caroli... 

Okamoto K and Yoshinaga J (1999) Proper use of reference materials for elemental speciation studies. In Fajgelt A and Parkany M, eds. The use of matrix reference materials in environmental analytical processes, pp 46-56. Royal Sodety of Chemistry, Cambridge. 

Today it has become clear that the effect of trace elements in living systems, in food, and in the environment depends on the chemical form in which the element enters the system and the final form in which it is present. The form, or species, clearly governs its biochemical and geochemical behaviour. lUPAC (the International Union for Pure and Applied Chemistry) has recently set guidelines for terms related to chemical speciation of trace elements (Templeton et al. 2000). Speciation, or the analytical activity of measuring the chemical species, is a relatively new scientific field. The procedures usually consist of two consecutive steps (i) the separation of the species, and (2) their measurement An evident handicap in speciation analysis is that the concentration of the individual species is far lower than the total elemental concentration so that an enrichment step is indispensable in many cases. Such a proliferation of steps in analytical procedure not only increases the danger of losses due to incomplete recovery, chemical instability of the species and adsorption to laboratory ware, but may also enhance the risk of contamination from reagents and equipment. 

The list of elements and their species listed above is not exhaustive. It is limited to the relatively simple compounds that have been determined by an important number of laboratories specializing in speciation analysis. Considering the economic importance of the results, time has come to invest in adequate CRMs. There is a steadily increasing interest in trace element species in food and in the gastrointestinal tract where the chemical form is the determinant factor for their bioavailability (Crews 1998). In clinical chemistry the relevance of trace elements will only be fully elucidated when the species and transformation of species in the living system have been measured (ComeUs 1996 Cornelis et al. 1998). Ultimately there will be a need for adequate RMs certified for the trace element species bound to large molecules, such as proteins. 

Cornelis R (1996) Involvement of analytical chemistry in chemical speciation of metals in clinical samples. Ann Clin Lab Sd 26 252-263. 

Principles and Characteristics The fastest growing area in elemental analysis is in the use of hyphenated techniques for speciation measurement. Elemental spe-ciation analysis, defined as the qualitative identification and quantitative determination of the individual chemical forms that comprise the total concentration of an element in a sample, has become an important field of research in analytical chemistry. Speciation or the process yielding evidence of the molecular form of an analyte, has relevance in the fields of food, the environment, and occupational health analysis, and involves analytical chemists as well as legislators. The environmental and toxicological effects of a metal often depend on its forms. The determination of the total metal content... 

Applications Speciation analysis is particularly important in plant and animal biochemistry and nutrition (food/food supplements), clinical biochemistry, industrial chemistry and environmental chemistry. In the... 

L. Ebdon, L. Pitts, R. Comehs, H. Crews, O.F.X. Donard and Ph. Quevauviller (eds), Trace Element Speciation for Environment, Food, Health, The Royal Society of Chemistry, Cambridge (2001). 

Ph. Quevauviller, Methods Performance Studies for Speciation Analysis, The Royal Society of Chemistry, Cambridge (1998). 

Van Luik, A.E. and Jurinak, J.J., Equilibrium chemistry of heavy metals in concentrated electrolyte solution, in Chemical Modeling in Aqueous Systems Speciation, Sorption, Solubility and Kinetics, Jenne, E.A., Ed., ACS Symp. Series 93, American Chemical Society, Washington, 1979, pp. 683-710. 

Photothermal Spectroscopy Methods for Chemical Analysis. By Stephen E. Bialkowski Element Speciation in Bioinorganic Chemistry. Edited by Sergio Caroli Laser-Enhanced Ionization Spectrometry. Edited by John C. Travis and Gregory C. Turk Fluorescence Imaging Spectroscopy and Microscopy. Edited by Xue Feng Wang and Brian Herman... 

---