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PubMedDate not supplied

Distribution and speciation of metals in surface sediments of Taranto [corrected] gulf (Ionian Sea, Southern Italy).

Concentrations of metals (Al, Fe, Ti, Ni, Mn, Cr, Zn, Cu, Pb) were determined in surface sediments from Taranto gulf (Ionian Sea, Southern Italy) in order to assess the distribution and the bioavailability of metals. Total metal content and speciation of Fe, Ni, Mn, Zn, Cu and Pb were determined. Sediment cores were also sampled in some stations of particular interest. The analytical results show that metals distribution does not show significant variations in relation to depth. Metal distribution in the Taranto gulf is mainly influenced by industrial wastes from Taranto town, by rivers of the Basilicata region and by prevailing anticlockwise marine currents. These factors cause an accumulation of metals in the sediments near to the coasts of Calabria. The statistical analysis, effected by HCA and PCA methods, can be considered a good starting point in order to classify sediment samples and to locate accumulation areas. Metal speciation shows that Fe, Ni and Zn are present in sediments mainly as sulphides, Mn is present principally in an ion-exchange form or bound to carbonate, while Cu and Pb are mainly present in the fraction bounds to humic acids.

Geologic Sediments↗
PubMed2003

Molecular scale speciation of first-row transition elements bound to ligneous material by using X-ray absorption spectroscopy.

To develop a solid scientific basis for maintaining soil quality and formulating effective remediation strategies, it is critical to determine how environmentally-important trace metals are sequestered in soils at the molecular scale. The speciation of Mn, Fe and Cu in soil organic matter has been determined by synchrotron-based techniques: extended X-ray absorption fine structure (EXAFS) and X-ray absorption near edge structure (XANES). We show the structural similarity between the surface complexes of Mn(II), Fe(III) and Cu(II). These cations are bound to the surface through oxygen atoms. Each one presents a more or less tetragonal-distorted octahedral geometry. The use of X-ray absorption spectroscopy provides a relevant method for determining trace-metal speciation in both natural and contaminated environmental materials.

Journal Article↗
PubMed1998

Selenium speciation by interfacing capillary electrophoresis with inductively coupled plasma-mass spectrometry.

The high resolution potential of capillary electrophoresis (CE) makes CE techniques valuable for separations of selenium species. Further, inductively coupled plasma-mass spectrometry (ICP-MS) affords element-specific multi-element detection, providing extremely low detection limits. The combination of CE with ICP-MS promises to become a powerful tool for metal speciation. Therefore, an on-line hyphenation of CE with ICP-MS, which was developed earlier (Michalke, B., Schramel, P., Fresenius' J. Anal. Chem. 1997, 257, 594-599), was modified and applied to selenium speciation. For this reason, capillary zone electrophoresis (CZE) methods were developed, providing the possibility to analyze six Se species of interest in one run: Se (IV), Se (VI), selenium carrying glutathione (GSSeSG), selenomethionine (SeM), selenocystine (SeC), and selenocystamine (SeCM). The final CE method used an alkaline background electrolyte (Na2CO3/NaOH) with separation differentiated from the detection step during hyphenation. This resulted in short separation times (10 min) and a subsequent detection step of 100s. The Se species were sufficiently separated from each other and appeared at 7s (SeCM), 16s (Se [VI]), 22s [SeC], 27s (Se [IV]), 35s [SeM] and 56s (GSSeSG) during the detection step. Detection limits were calculated as 10 or 20 microg Se/L for inorganic Se species and 35-50 microg Se/L for organic Se species.

Electrophoresis, Capillary↗
PubMed2003

Capillary electrophoresis speciation of chromium in leather tanning liquor.

We present a method for the speciation of chromium by capillary electrophoresis. Cr(III) was complexed with diethylenetriaminepentaacetic acid (DTPA) to form a negatively charged complex. Using 20 mM phosphate buffer of pH 8 containing 0.5 mM tetradecyltrimethylammonium hydroxide (TTAOH) at a separation voltage of -15 kV, both forms of chromium CrDTPA(2-) and CrO(4) (2-) were separated in less than 6 min. Direct UV detection at 214 nm was used. The effect of the presence of interfering ions was investigated. The application of the developed method to speciation of chromium in tanning liquor is demonstrated. The obtained results have shown a good correlation with those of flame atomic absorbance spectrometry (FAAS), inductively coupled plasma-mass spectrometry (ICP-MS) and UV/VIS spectrophotometry.

Chromium↗
PubMed2004

Speciation of protein-bound trace elements by gel electrophoresis and atomic spectrometry.

The metabolism of trace elements, in particular their binding to proteins in biological systems is of great importance in biochemical, toxicological, and pharmacological studies. As a result there has been a sustained interest over the last two decades in the speciation of protein-bound metals. Various analytical approaches have been employed, combining efficient separation of metalloproteins by liquid chromatography or electrophoresis with high-sensitivity elemental detection. Slab-gel electrophoresis (GE) is a key platform for high-resolution protein separation, and has been combined with autoradiography and various atomic spectrometric techniques for in-gel determination of protein-bound metals. Recently, the combination of GE with state-of-the-art inductively coupled plasma-mass spectrometry (ICP-MS), particularly when linked to laser ablation (LA) for direct gel interrogation, has opened up new opportunities for rapid characterization of metalloproteins. The use of GE and atomic spectrometry for the speciation of protein-bound trace elements is reviewed in this paper. Technical requirements for gel electrophoresis/atomic spectrometric measurement are considered in terms of method compatibilities, detection capability and potential usefulness. The literature is also surveyed to illustrate current status and future trends.

Autoradiography↗
PubMed2005

Capillary electrophoresis on-line coupled with hydride generation-atomic fluorescence spectrometry for speciation analysis of selenium.

A new method for speciation analysis of two inorganic selenium species was developed by on-line coupling of capillary electrophoresis (CE) with hydride generation-atomic fluorescence spectrometry (HG-AFS) and on-line conversion of Se(VI) to Se(IV). Baseline separation of Se(VI) and Se(IV) was achieved by CE in a 50 cm x 75 microm inside diameter (ID) fused-silica capillary at -20 kV using a mixture of 15 mmol.L(-1) NaH2PO4 and 0.5 mmol.L(-1) cetyltrimethylammonium bromide (pH 7.5) as electrolyte buffer. Se(VI) was on-line reduced to Se(IV) by mixing the CE effluent with concentrated HCl. The precision (relative standard deviation, RSD, n=7) ranged from 0.7 to 1.3% for migration time, 6.4 to 3.7% for peak height response, and 5.9 to 6.1% for peak area for the two selenium species at the 500 microg.L(-1) (as Se) level. The detection limits were 33 and 25 microg.L(-1) (as Se) for Se(VI) and Se(IV), respectively. The recoveries of the two selenium species in five locally collected water samples ranged from 88 to 114%. The developed method was applied to speciation analysis of inorganic selenium species in spiked natural water samples.

Electrophoresis, Capillary↗
PubMed2005

Speciation of arsenic compounds in fish and oyster tissues by capillary electrophoresis-inductively coupled plasma-mass spectrometry.

A capillary electrophoresis-inductively coupled plasma-mass spectrometric (CE-ICP-MS) method for the speciation of six arsenic compounds, namely arsenite [As(III)], arsenate [As(V)], monomethylarsonic acid, dimethylarsinic acid, arsenobetaine and arsenocholine is described. The separation has been achieved on a 70 cm length x 75 microm ID fused-silica capillary. The electrophoretic buffer used was 15 mM Tris (pH 9.0) containing 15 mM sodium dodecyl sulfate (SDS), while the applied voltage was set at +22 kV. The arsenic species in biological tissues were extracted into 80% v/v methanol-water mixture, put in a closed centrifuge tube and kept in a water bath, using microwaves at 80 degrees C for 3 min. The extraction efficiencies of individual arsenic species added to the sample at 0.5 microg As/g level were between 96% and 107%, except for As(III), for which it was 89% and 77% for oyster and fish samples, respectively. The detection limits of the species studied were in the range 0.3-0.5 ng As/mL. The procedure has been applied for the speciation analysis of two reference materials, namely dogfish muscle tissue (NRCC DORM-2) and oyster tissue (NIST SRM 1566a), and two real-world samples.

Animals↗
PubMed2006

Speciation of chromium by selective separation and preconcentration of Cr(III) on an immobilized nanometer titanium dioxide microcolumn.

Nanometer titanium dioxide immobilized on silica gel (immobilized nanometer-scale TiO2 particles) was prepared by a sol-gel method and characterized by X-ray diffraction and scanning electron microscopy. The adsorptive behavior of Cr(III) and Cr(VI) on immobilized nanometer TiO2 was assessed. Cr(III) was selectively sorbed on immobilized nanometer TiO2 in the pH range of 7-9, while Cr(VI) was found to remain in solution. A sensitive and selective method has been developed for the speciation of chromium in water samples using an immobilized nanometer TiO2 microcolumn and inductively coupled plasma atomic emission spectrometry. Under optimized conditions (pH 7.0, flow rate 2.0 mL/min), Cr(III) was retained on the column, then eluted with 0.5 mol/L HNO3 and determined by ICP-AES. Total chromium was determined after the reduction of Cr(VI) to Cr(III) by ascorbic acid. The adsorption capacity of immobilized nanometer TiO2 for Cr(III) was found to be 7.04 mg/g. The detection limit for Cr(III) was 0.22 ng/mL and the RSD was 3.5% (n = 11, c = 100 ng/ mL) with an enrichment factor of 50. The proposed method has been applied to the speciation of chromium in water samples with satisfactory results.

Adsorption↗
PubMed2006

Cloud point extraction combined with electrothermal vaporization inductively coupled plasma mass spectrometry for the speciation of inorganic selenium in environmental water samples.

A new method based on cloud point extraction (CPE) separation and electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICPMS) detection has been proposed for the speciation of inorganic selenium in environmental waters. When the temperature of the system is higher than the cloud point temperature (CPT) of the selected surfactant Triton X-114, the complex of Se(IV) with ammonium pyrrolidine dithiocarbamate (APDC) seems to be extracted into the surfactant-rich phase, whereas the Se(VI) remains in aqueous solutions. Thus, an in situ separation of Se(IV) and Se(VI) could be realized. The concentrated analyte was introduced into the ETV-ICP mass spectrometer for determination of Se((IV) after dilution with 200 microL methanol. Se(VI) was reduced to Se(IV) prior to determining total selenium, and its assay was based on subtracting Se(IV) from total selenium. The main factors affecting the CPE and the vaporization behavior of the analyte were investigated in detail. Under the optimized experimental conditions, the limit of detection (LOD) for Se(IV) was 8.0 ng/L with an enhancement factor of 39 when 10 mL of sample solution was preconcentrated to 0.2 mL. The relative standard deviation (RSD) was found to be 3.9% (C(Se(IV)) = 1.0 microg/L, n = 7). The proposed method was applied to the speciation of inorganic selenium in different environmental water samples with the recovery for the spiked samples in the range of 82-102%.

Environmental Monitoring↗
PubMed1998

Chemical speciation dynamics and toxicity assessment in aquatic systems.

The key to risk assessment of contaminant effects in the environment (water, sediments, soil) is the ability to document cause-and-effect relationships. In ecotoxicological research, biotic responses are related to quantified contaminant concentrations, which in most cases are still expressed in terms of "total elemental concentration" and not in terms of "elemental species." However, it becomes evident that the abundance and distribution of pollutants in the environment, their bioavailability, and their toxicity to aquatic and terrestrial organisms (including humans) can often be better understood in terms of "elemental species." The persistence, mobility, chemical reactivity, sorption dynamics, and so on of contaminants in soil and water are governed by a range of changing physicochemical parameters (pH, temperature, organic matter, suspended solids, etc.), which finally dictate the effects at the organism level. Examples are given to demonstrate that knowledge of the nature and concentration of elemental species of pollutants is crucial in assessing the impact of contaminants on aquatic ecosystems. The experimental approach to evaluate chemical speciation dynamics in relation to toxic effects is illustrated in a case study on the acute toxicity of aluminum in mixing zones at the confluence of rivers with different pH values. This study under nonequilibrium ecosystem conditions has provided new insights into the mechanism of toxicity of aluminum to freshwater organisms. In conclusion, an integrative approach by environmental chemists and ecotoxicologists is recommended to evaluate environmental pollution. Studies on the assessment of the impact of changing physicochemical parameters on the transformation kinetics and chemical speciation of pollutants, which finally determine toxicity and bioconcentration in organisms, deserve more attention in environmental toxicology.

Aluminum↗
PubMed1999

Effects of organic pollutants on soil microbial activity: the influence of sorption, solubility, and speciation.

The Fe(III) reduction test was used to measure the toxicity of 12 organic chemicals [dichlorophenoxyacetic acid (2,4-D), trichlorophenoxyacetic acid (2,4,5-T), atrazine, picloram, 4-chlorobenzeneamine, pentachlorophenol (PCP), hexachlorobenzene (HCB), 1,1-bis-4-chlorophenyl-2,2,2-trichloroethane (DDT), trichloroethene, benzene, phenol, linear alkylbenzenesulfonate (LAS)]. The different inherent toxicity of the pollutants is strongly modified by interactions with the soils. The total amounts that cause 10, 50, and 90% inhibitions (effective doses, ED10, ED50, ED90) can be statistically related to soil parameters that control the sorption and solubility of the chemicals. Sorption experiments with 2,4-D, 2,4,5-T, PCP, and LAS confirm that the degree of sorption and the concentration in the soil solution are important for potential toxic effects. However, toxic solution concentrations of a chemical (effective concentrations, EC10, EC50, EC90) also vary considerably. For some chemicals the influence of soil pH on their speciation in the soil solution is mainly responsible for this, e.g., the transformation from anionic to nonionic species with decreasing pH. The nonionic species of 2,4-D, 2,4,5-T, and PCP formed under acidic conditions are more toxic than the anionic species. Thus, depending on the chemical parameters of the soils that determine the degree of sorption and the speciation of toxicants in the liquid phase, soils either can "buffer" high loads of toxicants or can be very sensitive toward contamination.

Dose-Response Relationship, Drug↗
PubMed1993

Adaptation on fluctuating fitness landscapes: speciation and the persistence of lineages.

The NK landscape model of adaptive evolution introduced by Kauffman & Levin (1987) is modified to simulate diversification of monophyletic lineages. Extinction probability is made a function of fitness, and speciation probability a function of the number of fitter one mutant neighbors, which is analogous to genetic potential. Dynamics of adaptive walks are measured as the total number of phenotypically defined species per generation. Changes in species number are described for static and varying landscapes. Persistence of lineages is incompatible with static fitness landscapes and requires that most component species do not reach adaptive optima. Differences in N:K ratios, and therefore in morphological integration, strongly affect speciation rates and could play a role in species sorting.

Adaptation, Physiological↗
PubMed2001

Differences in (G+C) content between species: a commentary on Forsdyke's "chromosomal viewpoint" of speciation.

Forsdyke (1999) has recently argued that differences in (G+C)%, or G+C content, may trigger new species formation. He further argues that the genic model has shortcomings that can be overcome by his "chromosomal" (hereafter, "G+C") model. We disagree on several counts. First, we do not accept that the genic model has the shortcomings suggested by Forsdyke. There is an abundance of empirical support for the contribution of individual genes, as well as of mapped chromosomal regions, to post-zygotic reproductive isolation (and Haldane's rule). Further, we argue that the G+C model suffers from the same theoretical difficulties as other speciation models based on underdominance. We also question the evidence Forsdyke uses to support his model. Finally, we describe analyses of G+C content in a well-studied model system of speciation (the Drosophila melanogaster species complex), the results of which are incompatible with the G+C model. Thus, while Forsdyke's G+C model cannot be explicitly ruled out, it is not directly supported by empirical data. In contrast, the genic model is well supported by empirical data, holds up on theoretical grounds, and does not require any assistance from the G+C model.

Animals↗
PubMed2000

Molecular phylogenetics of the holly leafminers (Diptera: Agromyzidae: Phytomyza): species limits, speciation, and dietary specialization.

A molecular phylogenetic analysis was conducted to determine relationships and to investigate character evolution in the Phytomyza ilicis group of leafmining flies on hollies (Aquifoliaceae: Ilex). A total of 2207 bp of the mitochondrial cytochrome oxidase I and II genes were sequenced for all known holly leafminers, as well as for several undescribed members of this group. Maximum-parsimony analysis of the sequence data indicates that these leafminers form a monophyletic group with the inclusion of an undescribed leafminer that feeds on the distantly related plant Gelsemium sempevirens (Loganiaceae). Species boundaries of previously known and of undescribed holly leafmining species were confirmed with the molecular data, with one exception. Optimization of variable ecological and morphological characters onto the most parsimonious phylogeny suggests that these traits are evolutionarily labile, requiring multiple instances of convergence and/or reversal to explain their evolutionary history. Speciation in holly leafminers is associated with host shifts and appears to involve colonization of new hosts more often than cospeciation as the hosts diverge. Monophagy is the most common feeding pattern in holly leafminers, and more generalized feeding is inferred to have evolved at least two separate times, possibly as a prelude to speciation.

Animals↗
PubMed1994

The role of molecular genetics in speciation studies.

Systematists and population geneticists can both use molecular data sets to construct evolutionary trees (species and gene trees, respectively), and then use the resulting historical framework to test a variety of hypotheses. The greatest prospect for future advances in our understanding of speciation is to extend these historical approaches to the species/population interface, for only by straddling this interface can we actually study the processes involved in the origin of a new species. This chapter illustrates how the bottom-up historical approaches used in population genetics can be extended upwards to this critical interface in order to separate the effects of population structure from population history, to rigorously test the species status of a group, and to test hypotheses about the process of speciation by using gene trees to define a nested, statistical analysis of biogeographic and other types of data.

Animals↗
PubMed1990

Cadmium speciation studies in the intestine of Lumbricus terrestris by electrophoresis of metal proteins complexes.

Cadmium speciation of the intestinal compartment of the earthworm species, Lumbricus terrestris, has been investigated using polyacrylamide gel electrophoresis under non-denaturing conditions. Worms exposed to Cd(NO3)2 supplemented soils have been studied and compared to control samples. Prior to electrophoresis, the worm intestines were removed and dissected. Proteins in the crude intestinal extracts were separated using polyacrylamide gel electrophoresis. The cadmium distribution in the proteins has also been described. In a second set of experiments, cadmium bound to proteins was first isotopically exchanged with labelled cadmium (109Cd) and then cadmium speciation was performed using gel electrophoresis. Autoradiography of this gel shows an intense band in the contaminated sample whereas this band was absent in the control sample. These results show that one type of major protein has a strong affinity for cadmium in the worm intestinal extract. This type of protein had a migration close of that of rabbit liver metallothionein used for comparison.

Animals↗
PubMed1979

A comparison of interfertility and in vitro DNA-DNA reassociation as criteria for speciation in the genus Kluyveromyces.

Hybridization studies based on the use of the prototrophic selection technique were undertaken to compare interfertility and DNA-DNA reassociation as criteria for speciation purposes in the yeast genus Kluyveromyces. Degrees of DNA-DNA reassociation greater than 70% between strains, as reported in the literature, were found to correlate with high recombination frequencies. Degrees of DNA-DNA reassociation less than 20% between strains did, however, not invariably coincide with the absence of interfertility between strains. If interfertility is accepted as criterion for conspecificity, the hitherto reported low degrees (less than 20%) of DNA-DNA reassociation in Kluyveromyces cannot confidently be employed for speciation purposes.

Ascomycota↗
PubMed1976

Olfactory discrimination as an isolating mechanism in speciating mole rats.

Olfactory discrimination was tested in two chromosome forms of the speciating fossorial rodent, Spalax ehrenbergi, in Israel. Females of the chromosome forms 2n = 52 and 2n = 58 were tested for male odour discrimination, the source of odour being either case litter or urine. Estrous females of both forms preferred homochromosomal odurs, whereas diestrous females showed no discrimination. These results suggest that olfactory discrimination may serve as a reproductive isolating mechanism in the speciation of mole rats.

Animals↗