Quantitative speciation

Anoxic water samples, because they contain little in the way of particles, are far easier than aquifer materials to develop radioassays for the measurement of arsenate reduction. Arsenic speciation quantitatively changes from arsenate to arsenite with vertical transition from the surface oxic waters to the anoxic bottom depths of stratified lakes and fjords (55,56). This also occurs in Mono Lake, California (57), a transiently meromictic, alkaline (pH = 9.8), and hypersaline (salinity = 70-90 g/L) soda lake located in eastern California (Fig. 11). The combined effects of hydrothermal sources coupled with evaporative concentration have resulted in exceptionally high ( 200 fiM) dissolved arsenate concentrations in its surface waters. Haloalkaliphilic arsenate-respiring bacteria have been isolated from the lake sediments (26), and sulfate reduction, achieved with... 

Instrumental Quantitative Analysis. Methods such as x-ray spectroscopy, oaes, and naa do not necessarily require pretreatment of samples to soluble forms. Only reUable and verified standards are needed. Other instmmental methods that can be used to determine a wide range of chromium concentrations are atomic absorption spectroscopy (aas), flame photometry, icap-aes, and direct current plasma—atomic emission spectroscopy (dcp-aes). These methods caimot distinguish the oxidation states of chromium, and speciation at trace levels usually requires a previous wet-chemical separation. However, the instmmental methods are preferred over (3)-diphenylcarbazide for trace chromium concentrations, because of the difficulty of oxidizing very small quantities of Cr(III). 

Ressler T, J Wong, J Roos, IL Smith (2000) Quantitative speciation of Mn-bearing particulates emitted from autos burning (methylcyclopentadienyl)manganese tricarbonyl-added gasolines using XANES spectroscopy. Environ Sci Technol 34 950-958. 

Applications Table 8.58 shows the main fields of application of inorganic mass spectrometry. Mass-spectrometric techniques find wide application in inorganic analysis, and are being used for the determination of elemental concentrations and of isotopic abundances for speciation and surface characterisation for imaging and depth profiling. Solid-state mass spectrometry is usable as a quantitative method only after calibration by standard samples. 

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... 

Russell and Rabenstein [43] described a speciation and quantitation method for underivatized and derivatized penicillamine, and its disulfide, by capillary electrophoresis. Penicillamine and penicillamine disulfide were determined by capillary electrophoresis on a capillary (24 cm x 25 pm i.d. or 50 cm x 50 pm i.d. for underivatized thiols) with detection at 357 nm (200 nm for underivatized thiols). The run buffer solution was 0.1 M phosphate (pH 2.3). Detection limits were 20-90 pM without derivatization, and 5-50 pM after derivatization. Calibration graphs were linear from 1 pM to 5 mM thiols. 

And finally, additional research is needed on mercury accumulation and detoxification in comparatively pristine ecosystems. Key uncertainties in understanding the process of mercury uptake in aquatic ecosystems, for example, include relations between water chemistry and respiratory uptake, quantitative estimates of intestinal tract methylation and depuration, and degree of seasonal variability in mercury speciation and methylation-demethylation processes (Post et al. 1996). 

Draper, W.M., D. Wijekoon, and R.D. Stephens. 1991. Speciation and quantitation of Aroclors in hazardous wastes based on congener data. Chemosphere 22 147-163. 

Bioaccumulation is a complicated process that couples numerous complex and interacting factors. In order to directly relate the chemical speciation of an element to its bioavailability in natural waters, it will be necessary to first improve our mechanistic understanding of the uptake process from mass transport reactions in solution to element transfer across the biological membrane. In addition, the role(s) of complex lability and mobility, the presence of competing metal concentrations and the role(s) of natural organic ligands will need to be examined quantitatively and mechanistically. The preceding chapter... 

Scheinost AC, Kretzschmar R, Pflster S, Roberts DR. Combining selective sequential extractions, X-ray absorption spectroscopy, and principal component analysis for quantitative zinc speciation in soil. Environ. Sci. Technol. 2002 36 5021-5028. 

Current EPA analytical methods do not allow for the complete speciation of the various hydrocarbon compounds. EPA Methods 418.1 and 8015 provide the total amount of petroleum hydrocarbons present. However, only concentrations within a limited hydrocarbon range are applicable to those particular methods. Volatile compounds are usually lost, and samples are typically quantitated against a known hydrocarbon mixture and not the specific hydrocarbon compounds of concern or the petroleum product released. By conducting EPA Method 8015 (Modified) using a gas chromatograph fitted with a capillary column instead of the standard, hand-packed column, additional separation of various fuel-ranged hydrocarbons can be achieved. 

IONIC SPECIATION. Ions interact continually in aqueous solution. Ions are complexed with water molecules. Even when we say that a certain ion is uncomplexed, the fact is that the ion is still complexed, in this case with water molecules. Association constants (also known in the literature as stability or formation constants) allow one to quantitate the extent to which an ion is complexed with any particular substance in solution. They also allow comparisons of the relative affinity of different complex-ing agents for a particular chemical substance. Speciation is a chain of linked binding functions (see Fig. 3). Such diagrams show the relative concentrations of the various complexes in solution, and the reversible equilibria existing between these pools are shown by the arrows. 

Manceau, A. Lanson, B. Schlegel, M.L. Harge, J.C. Musso, M. Eybert-Berard, L. Haze-marm, J.-L. Chateigner, D. Lamble, G.M. (2000) Quantitative Zn speciation in smelter-contaminated soils by EXAFS spectroscopy. Am. J. Sd. 300 289-343 Manceau, A. Nagy, K.L. Spadini, L. Ragnars-dottir, K.V. (2000 a) Influence of anionic layer structure of Fe-oxyhydroxides on the structure of Cd surface complexes. J. Colloid Interface Sd. 228 306-316... 

Individual VOC. The term VOC is commonly used to describe speciated measurements of individual organics. The almost universal approach to the identification and measurement of individual VOC is GC with either FID or mass spectrometry (MS). GC-MS is used to establish the identity of a particular compound through the combination of retention times and mass spectra and, of course, can also be used for quantification. However, for a given type of air mass, GC-FID is commonly used for more extensive quantitative measurements after the individual peaks have been identified. For reviews of various aspects of sampling and measurement of VOC in air, see Westberg and Zimmerman (1993), Apel et al. (1994), Klemp et al. (1994), Sacks and Akard (1994), and Dewulf and Van Langen-hove (1997). 

OSTERGREN, J. D., BROWN, G. E. JR., PaRKS, G. A. Tingle, T. N. 1999. Quantitative speciation of lead in selected mine tailings from Leadville, CO. Environmental Science Technology, 33, 1627-1636. 

Accuracy. Quantitative estimates of radionuclide solubility and speciation need reliable thermodynamic data, that is,... 

A speciation of particular interest is to detect the presence of species in different oxidation states in the sample. The determination of the presence of two or even more oxidation states of a given species, and eventually their relative quantitation, is a highly important analytical target in a variety of applications. The determination of the Fe III)/Fe II) ratio in raw and ceramic materials is probably one of the most... 

The book has been structured into roughly three parts. First (Chap. 1), an overview of analytical methods applied in the study of cultural goods is presented to situate electrochemical methods in their analytical context. The second part contains voltammetric methods devoted to the identification (Chap. 2), speciation (Chap. 3), and quantitation (Chap. 4) of microsample components from works of art and/or cultural and archaeological pieces. The third part of the book presents selected examples of the deterioration of metal artifacts, outlining aspects peculiar to the cultural heritage conservation field (Chap. 5), and describes hisforic and current issues regarding electrochemical techniques used in restoration treatments and preventive conservation (Chap. 6). 

Magnesium speciation (Section ni.A) in serum was carried out using an anion exchange column for protein separation, with mobile phase at pH 7.4 the effluent was collected in an automatic fraction collector. On-line quantitation of the protein fractions was carried out by DA-UVD, and Mg determination was carried out from the automatic sampler in a GFAAS apparatus, measuring at 202.8 nm . ... 

Multi-element trace analysis is an important prerequisite for the quality assurance of foodstuffs with respect to the characterization of non-essential, toxic and essential (nutrient) elements as pollutions or as mineral elements relevant to health. Contamination with heavy metals such as Cd, Pb or Hg has become a serious problem with increasing environmental (artificial) contamination e.g., due to industrial pollution. The increasing use of inorganic mass spectrometric techniques (especially of ICP-MS) in the analysis of foodstuffs for multi-element analysis of trace elements or the detection of selected elements and species at a low concentration level has resulted from advances in very sensitive and quantitative measurements of metals, metalloids and several non-metals, including their speciation. 

This chapter provides some insight into the chemistry of a number of commonly used polymeric sorbents. Particular focus is placed on the chemical identification of contaminants typically associated with each of the following types of polymeric sorbents Amberlite XAD resins, Ambersorb XE resins, and PUF. Emphasis is placed on the chemical speciation of solvent-extractable organic contaminants present in a number of these sorbents as received from the manufacturer. Both qualitative and quantitative data on a micrograms-per-gram (parts-per-million) basis are provided as determined by combined gas chromatography-mass spectrometry (GC-MS). 

Reduced forms of sulfur, such as sulfide and thiols, also react rapidly with Mn02 (26-28) as well as with FeOx. However, sulfur in fresh water is often present in substoichiometric amounts with respect to iron. Thus little or no free reduced S is present even under strongly anoxic conditions because of the formation of very insoluble FeS x species. Our equilibrium calculations (29) indicate that complexation with reduced sulfur species is not a quantitatively important aspect of Mn speciation in Lake Richard B. Russell (RBR). However, this result does not rule out the occurrence of such species as transient intermediates. 

The underlying chemistry of the organometals, which determines their tendency to speciate and which determines their molecular identification and analysis (qualitative and quantitative) in environmental or biological matrices. 

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