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PubMed2006

Speciation of Cr(III) and Cr(VI) in environmental samples by solid phase extraction on Ambersorb 563 resin.

A simple and sensitive method for the speciation, separation and preconcentration of Cr(VI) and Cr(III) in natural water, soil and sediment samples was developed. Cr(VI) has been separated from Cr(III) and preconcentrated as Cr(III)-diphenylcarbazone complex by using Ambersorb 563 resin and determined by spectrophotometric method at 540 nm. Effect of analytical parameters such as sulfuric acid concentration, ligand volume, type of elution solution, sample volume, amount of resin and foreign ions were investigated. The presented procedure was successfully applied for the chromium speciation in various environmental samples with successfully results.

Absorption↗
PubMed2006

Application of the Rietveld method to assess chromium(VI) speciation in chromite ore processing residue.

The Rietveld method allows the quantification of crystalline phases and amorphous material identified by X-ray powder diffraction (XRPD) and other diffraction methods. The method assists in determining the speciation of contaminants in solid matrices both qualitatively and quantitatively in a statistically defensible approach, as it does not focus on a microscale. Rietveld was applied to chromite ore processing residue (COPR), a cementitious waste containing hexavalent chromium. Calcium aluminum chromium oxide hydrates (CACs) were the crystalline phases identified by XRPD that bind Cr(6+) in COPR according to their chemical formula. Rietveld quantification, combined with mass balances on Cr(6+), showed that CACs may bind Cr(6+) in variable percentages, ranging from 25% to 85%. Analysis of duplicate samples showed that material variability is the predominant factor of uncertainty in evaluating the role of CACs in Cr(6+) speciation, provided that a consistent quantification strategy is pursued. The choice of strategy was performed on the basis of the pertinent literature, preliminary analyses of the equipment and the software settings, and mass balances. The correlation between the average CAC-bound Cr(6+) concentration and the total Cr(6+) for five samples (R(2)=0.94), extracted from different zones and soil borings, suggests that CACs are a primary sink for Cr(6+) in COPR.

Aluminum Oxide↗
PubMed2006

Speciation of Cr(III) and Cr(VI) after column solid phase extraction on Amberlite XAD-2010.

A speciation procedure for Cr(III) and Cr(VI) based on column solid phase extraction on Amberlite XAD-2010 and flame atomic absorption spectrometry combination. Cr(VI) was quantitatively recovered on Amberlite XAD-2010 resin at pH range of 2.0-3.0 as its diethyldithiocarbamate complex, while the recoveries of Cr(III) was below 5%. The influences of the various parameters including amounts of the reagents, eluent type and its volume, sample volume, etc., on the quantitative recoveries were examined. The interference of matrix and coexistent elements for method were studied. The detection limit (corresponding to three times the standard deviation of the blank) and the enrichment factor for Cr(VI) were found to be 1.28 microg/L and 25, respectively. To verify the accuracy of the method, drinking water certified reference material (CRM-TMDW-500) was analyzed and the results obtained were in good agreement with the certified value. The proposed method has been successfully applied to the speciation of Cr(III) and Cr(VI) in water samples and preconcentration of total chromium in environmental samples.

Chromium↗
PubMed2006

Cr(VI) and Cr(III) speciation on Bacillus sphaericus loaded diaion SP-850 resin.

A speciation procedure for chromium(III) and chromium(VI) in the environmental samples has been established in the presented work. The procedure presented based on quantitative biosorption of chromium(III) on Bacillus sphaericus loaded Diaion SP-850 at pH 5. The Cr(VI) recoveries at pH 5 were below 5% on the biosorbent. After reduction of Cr(VI) by concentrated H(2)SO(4) and ethanol, the system was applied to the total chromium. Cr(VI) was calculated as the difference between the total chromium content and the Cr(III) content. Optimal analytical conditions including pH, amounts of biosorbent, etc. for Cr(III) recoveries were investigated. The influences of the some alkaline and earth alkaline ions and some transition metals on the recoveries were also investigated. The capacity of biosorbent for chromium(III) was 6.95 mgg(-1). The detection limit (3 sigma) of the reagent blank for chromium(III) was 0.50 microgL(-1). The procedure was successfully applied to the speciation of chromium(III) and chromium(VI) in natural water samples (R.S.D. lower than 5%, recoveries greater than 95%).

Adsorption↗
PubMed2004

Proteomic traces of speciation.

Recent work has shown that the network of structural similarity between protein domains exhibits a power-law distribution of edges per node. The scale-free nature of this graph, termed the protein domain universe graph or PDUG, may be reproduced via a divergent model of structural evolution. The performance of this model, however, does not preclude the existence of a successful convergent model. To further resolve the issue of protein structural evolution, we explore the predictions of both convergent and divergent models directly. We show that when nodes from the PDUG are partitioned into subgraphs on the basis of their occurrence in the proteomes of particular organisms, these subgraphs exhibit a scale-free nature as well. We explore a simple convergent model of structural evolution and find that the implications of this model are inconsistent with features of these organismal subgraphs. Importantly, we find that biased convergent models are inconsistent with our data. We find that when speciation mechanisms are added to a simple divergent model, subgraphs similar to the organismal subgraphs are produced, demonstrating that dynamic models can easily explain the distributions of structural similarity that exist within proteomes. We show that speciation events must be included in a divergent model of structural evolution to account for the non-random overlap of structural proteomes. These findings have implications for the long-standing debate over convergent and divergent models of protein structural evolution, and for the study of the evolution of organisms as a whole.

Bacterial Proteins↗
PubMed2005

Metal speciation and environmental impact on sandy beaches due to El Salvador copper mine, Chile.

Several coastal rocky shores in northern Chile have been affected by the discharges of copper mine tailings. The present study aims to analyze the chemical speciation of heavy metals in relation to the diversity of sessile species in the rocky intertidal benthic community on the northern Chilean coast, which is influenced by the presence of copper mine tailings. In particular, the chemical forms of Cd, Cu, Fe, Mn, Ni, Pb and Zn in beach sediment samples collected in the area influenced by El Salvador mine tailings were studied using a sequential chemical extraction method. In general, all the elements present a maximum concentration in the area near the actual discharge point (Caleta Palito). With regard to Cu and Mn, the concentrations range between 7.2-985 and 746-22,739 microg/g respectively, being lower than background levels only in the control site of Caleta Zenteno. Moreover, the correlation coefficients highlight that Fe, Mn and Ni correlate significantly and positively in the studied area, showing a possible common, natural origin, whilst Cu shows a negative correlation with Fe, Mn and Ni. It could be possible that Cu has an anthropogenic origin, coming from mining activity in the area. Cd, Fe, Mn, Ni, Pb and Zn are mostly associated with the residual phase, whilst Cu presents a different speciation pattern, as resulted from selective extractions. In fact, Cu is highly associated with organic and exchangeable phases in contaminated localities, whilst it is mainly bound to the residual phase in control sites. Moreover, our results, compared to local biological diversity, showed that those sites characterized by the highest metal concentrations in bioavailable phase had the lowest biodiversity.

Biodiversity↗
PubMed2005

Evaluation of DGT as a metal speciation tool in wastewater.

This paper aims to evaluate the performance of the diffusive gradient in thin film technique (DGT) as a speciation tool for metals in wastewater. The validity of metal sampling by DGT in wastewater was checked. DGT was used in parallel with the Daphnia magna acute toxicity test in order to obtain information on the speciation of copper and cadmium in diluted and spiked filtered wastewater (raw and treated) from two treatment plants. Combining the chemical (DGT) and the biological methods (D. magna toxicity test) allowed metal to be fractionated into inorganic, labile organic and inert organic metal. Copper was mainly found as inert organic complexes, whereas the major part of cadmium was found to be labile organic complexes. The proportion of inert organic copper complexes was higher in the presence of treated wastewater than in raw wastewater. The use of restricted gels in DGT devices discriminated more labile organic cadmium than labile organic copper, indicating that cadmium weak ligands have more complex structures than copper weak ligands. In our experimental conditions (i.e. a high metal to ligand ratio), DGT, even equipped with restricted gels, was able to accumulate labile organic complexes. This result highlights that the ecotoxicological interpretation of DGT measurement should be considered carefully. DGT is a reliable tool to assess the chemical characteristics of metals (i.e. reactivity) in wastewater, but it does not ensure that only inorganic metal is measured.

Animals↗
PubMed2006

PM10 speciation and determination of air quality target levels. A case study in a highly industrialized area of Spain.

The paper shows how PM speciation studies allow the evaluation of the strategies to be followed to diminish PM pollution in highly industrialized areas with a large number of potential pollution sources. Evolution of levels and speciation of PM10 in the ceramic producing area of Castelló (East Spain) was studied from April 2002 until December 2005. PM10 levels were measured at one rural (Borriana-rural), two suburban (Almassora and Onda) and three urban (Borriana-urban, L'Alcora and Vila-real) sites, all influenced by the ceramics industry. Average PM10 levels varied between 27 and 36 microg/m3 for the study period. Evaluation of 1996-2005 PM data from Onda shows a clear decrease of PM levels since the beginning of 2002. Summer peak levels and winter minima occurred at both rural and suburban sites, whereas urban sites had no clear seasonal trend, with high PM10 episodes being due variously to local, regional, and African dust intrusion events. PM10 chemical analysis at four of the sites showed the dominant constituent to be mineral matter, exceeding by 5-12 microg/m3 the usual ranges of annual mineral loadings in PM10 at comparable Spanish urban or regional background sites with no industrial influence. Given current PM10 loadings, we recommend a lowering target of 3-5 microg/m3 of the annual mean at the urban sites, which should be achievable given available emission abatement techniques.

Air Pollution↗
PubMed2006

Simultaneous tracing of 76Se-selenite and 77Se-selenomethionine by absolute labeling and speciation.

Nutritional selenocompounds are transformed into the assumed common intermediate selenide, which is utilized for the synthesis of selenoenzymes or transformed into methylated metabolites for excretion. Hence, selenocompound metabolites can be traced only with labeled selenium. Here we applied a new tracer method for the metallomics of biometals using simultaneous speciation of each metallome labeled with different homo-elemental isotopes to metabolism and availability of selenium. Rats were depleted of endogenous natural abundance selenium by feeding a single selenium stable isotope ((82)Se-selenite) and then administered (76)Se-selenite and (77)Se-selenomethionine ((77)Se-SeMet)simultaneously. Biological samples were subjected to quantification and speciation analysis by HPLC-ICPMS. Metabolites of the labeled (76)Se and (77)Se and interaction with endogenous selenium were traced and examined without interference from the corresponding endogenous natural abundance isotopes. Differences in the distribution and metabolism among organs and between the two nutritional selenocompounds were compared under exactly identical biological and analytical conditions: (1) selenite was distributed more efficiently than SeMet in organs and body fluids except the pancreas. (2) SeMet was taken up by organs in its intact form. (3) Selenium of SeMet origin was distributed selectively in the pancreas and mostly bound to a protein together with intact SeMet. (4) Selenosugars A and B but not trimethylselenonium (TMSe) were detected in the liver. (5) Selenosugar B and TMSe were detected in the kidneys.

Animals↗
PubMed2005

Characterization of cadmium uptake in human intestinal crypt cells HIEC in relation to inorganic metal speciation.

Cadmium (Cd) uptake was studied under inorganic exposure conditions in normal human intestinal crypt cells HIEC. The uptake time course of 0.3 microM Cd in a serum-free chloride medium was analyzed according to a first order equation with rapid initial (U0) and maximal (Umax) accumulation values of 14.1+/-1.4pmol/mgprotein and 41.4+/-2.0 pmol/mgprotein, respectively. The presence of a 300-fold excess of unlabeled Cd dramatically decreased tracer uptake, showing the involvement of specific mechanism(s) of transport. Our speciation studies revealed the preferential uptake of the free ion Cd2+, but also suggested that CdCln(2-n) species may contribute to Cd accumulation. Specific mechanisms of transport of very high and similar affinity (Km approximately 5 microM) have been characterized under both chloride and nitrate exposure conditions, but a two-fold higher capacity (Vmax) was estimated in the nitrate medium used to increase [Cd2+] over chlorocomplex formation. A clear inhibition of 109Cd uptake was observed at external acidic pH under both exposure media. An La-inhibitible 46% increase in 109Cd uptake was obtained in nominally Ca-free nitrate medium, whereas Zn provided additional inhibition. These results show different kinetic parameters for Cd uptake as a function of inorganic metal speciation. Cd2+ uptake would not involve the H+-coupled symport NRAMP2 but would be related instead to the Ca and/or Zn pathways. Because proliferative crypt cells play a critical role in the renewal process of the entire intestinal epithelium, studies on the impact of Cd on HIEC cell functions clearly deserve further investigation.

Algorithms↗
PubMed2004

Recent speciation in the Formica rufa group ants (Hymenoptera, Formicidae): inference from mitochondrial DNA phylogeny.

This study examines phylogenetic relationships among six species of the Formica rufa group ants (F. polyctena, F. rufa, F. lugubris, F. paralugubris, F. aquilonia, and F. pratensis). The phylogeny based on a 2051bp fragment of mtDNA including cyt b, tRNASer, and ND1 genes supports the division of the group into three major clusters: one with the species F. polyctena and F. rufa, one with F. aquilonia, F. lugubris, and F. paralugubris, and the third one with F. pratensis. The interspecific divergence estimates (mean 0.98 +/- 0.15% for the main phylogenetic groups) imply that radiation took place during the Pleistocene. Comparison of the divergence estimates among the F. rufa group species with divergence estimates among other closely related species of insects suggests that speciation in the group was relatively fast, and the mitochondrial lineages of F. polyctena and F. rufa have not fully separated. The haplotype tree shows also signs of transfer of mtDNA between species through hybridisation. The distribution of polygyny (multiple queens per nest) along the branches of the tree indicates that the social type characterised by highly polygynous societies and large colonial networks, has originated at least three times. The species F. aquilonia and F. paralugubris that build such large supercolonies, cluster tightly together with very little nucleotide variation, suggesting that this type of social organisation could be a factor promoting speciation in the ants.

Animals↗
PubMed2005

Speciation history of the North American funnel web spiders, Agelenopsis (Araneae: Agelenidae): phylogenetic inferences at the population-species interface.

Intra- and interspecific relationships of 12 out of 13 described species as well as a potential new species in the spider genus Agelenopsis (Araneae: Agelenidae) were analyzed using sequence data from two mitochondrial genes, cytochrome oxidase I (COI) and 16S ribosomal RNA. Approximately half of the species examined formed well-supported monophyletic groups, whereas the rest of the species were part of well-supported monophyletic species groups. Rather than viewing cases where species were not identified as being monophyletic as poor taxonomy, these cases more likely represent recent speciation and offer insights into the process of speciation. The clade with the lowest levels of interspecific sequence divergence was found in eastern North America, whereas western species displayed much higher levels of interspecific divergence. These patterns appear to extend below the species level as well, with southwestern species exhibiting the highest levels of intraspecific sequence divergence and geographic structuring. The relationship between Agelenopsis and Barronopsis, a genus once considered a sub-genus of Agelenopsis, was also examined. The two genera are reciprocally monophyletic but more generic level sampling is needed to confirm an apparent sister relationship between the two.

Animals↗
PubMed2006

Genetic divergence and speciation in lowland and montane peruvian poison frogs.

Amazonia is famous for high biodiversity, and the highlands of the transition zone between the Andes and the lowlands of the Amazon basin show particularly high species diversity. Hypotheses proposed to explain the high levels of diversity in the highlands include repeated parapatric speciation across ecological gradients spanning the transition zone, repeated allopatric speciation across geographic barriers between the highlands and lowlands, divergence across geographic barriers within the transition zone, and simple lineage accumulation over long periods of time. In this study, we investigated patterns of divergence in frogs of the genus Epipedobates (family Dendrobatidae) using phylogenetic and biogeographic analyses of divergence in mitochondrial DNA (1778 aligned positions from genes encoding cyt b, 12S and 16S rRNA for 60 Epipedobates and 11 outgroup specimens) and coloration (measured for 18 specimens representing nine species in Epipedobates). The majority of phenotypic and species diversity in the poison frog genus Epipedobates occurs in the transition zone, although two morphologically conserved members of the genus are distributed across the lowlands of the Amazon basin. Phylogenetic analysis reveals that there is a single highland clade derived from an ancestral colonization event in northern Peru by a population of lowland ancestry. Epipedobates trivittatus, a widespread Amazonian species, is a member of the highland clade that reinvaded the lowlands. Comparative analyses of divergence in coloration and mtDNA reveals that divergence in coloration among populations and species in the highlands has been accelerated relative to the lowlands. This suggests a role for selection in the divergence of coloration among populations and species.

Animals↗
PubMed1997

Parasite speciation within or between host species?--phylogenetic evidence from site-specific polystome monogeneans.

Partial nuclear 28S ribosomal RNA and mitochondrial cytochrome c oxidase subunit I (COI) gene sequences (953 and 385 nucleotides, respectively) of one fish monogenean (outgroup) and six polystome monogeneans (four Polystomoides spp. from the oral cavities and urinary bladders of freshwater turtles in Australia and Malaya, two Neopolystoma spp. from the urinary bladder and conjunctival sac of a freshwater turtle in Australia) were used to examine the question of whether congeneric species infecting different sites in the same host species have speciated in that host by adapting to different sites, or whether species infecting a particular site in one host have given rise to species infecting the same site in different hosts. Results show unequivocally that congeneric species infecting the same site, even of host species belonging to different suborders and occurring on different continents, are more closely related than congeneric species infecting different sites of the same host species. This is interpreted as meaning that speciation has not occurred in one host. Morphological evolution of polystomes has been very slow: few differences between species and even genera have evolved over a period of at least 150 Myr, and this is matched by low substitution rates of nucleotides, and the ambiguous position of species of different genera, depending on whether COI or 28S rDNA sequences are used.

Animals↗
PubMed2000

Speciation of selenium compounds with ion-pair reversed-phase liquid chromatography using inductively coupled plasma mass spectrometry as element-specific detection.

For selenium speciation analysis, the hyphenation of chromatographic separation with element-specific detection has proved a useful technique. A powerful separation system, which is capable of resolving several biologically and environmentally important selenium compounds in a single column, is greatly needed. However, that has been difficult to achieve. In this paper eight selenium compounds, namely, selenite [Se(IV)], selenate [Se(VI)], selenocystine (SeCys), selenourea (SeUr), selenomethionine (SeMet), selenoethionine (SeEt), selenocystamine (SeCM) and trimethylselenonium ion (TMSe+), were separated by using mixed ion-pair reagents containing 2.5 mM sodium 1-butanesulfonate and 8 mM tetramethylammonium hydroxide as a mobile phase. The separation of these anionic, cationic and neutral organic selenium compounds on a LiChrosorb RP18 reversed-phase column took only 18 min at a flow-rate of 1.0 ml/min with isocratic elution, and baseline separation among the six organic Se compounds was achieved. Inductively coupled plasma mass spectrometry (ICP-MS) was employed as element-specific detection. A comparison of ICP-MS signal intensity obtained with a Barbington-type nebulizer and with an ultrasonic nebulizer (USN) was made. Different signal enhancement factors were observed for the various selenium compounds when a USN was used. The speciation technique was successfully applied to the study on chemical forms of selenium in a selenium nutritional supplement. Selenomethionine was found to be the predominant constituent of selenium in the supplement.

Chromatography, High Pressure Liquid↗
PubMed2003

The potential of organic (electrospray- and atmospheric pressure chemical ionisation) mass spectrometric techniques coupled to liquid-phase separation for speciation analysis.

The use of mass spectrometry based on atmospheric pressure ionisation techniques (atmospheric pressure chemical ionisation, APCI, and electrospray ionisation, ESI) for speciation analysis is reviewed with emphasis on the literature published in and after 1999. This report accounts for the increasing interest that atmospheric pressure ionisation techniques, and in particular ESI, have found in the past years for qualitative and quantitative speciation analysis. In contrast to element-selective detectors, organic mass spectrometric techniques provide information on the intact metal species which can be used for the identification of unknown species (particularly with MS-MS detection) or the confirmation of the actual presence of species in a given sample. Due to the complexity of real samples, it is inevitable in all but the simplest cases to couple atmospheric pressure MS detection to a separation technique. Separation in the liquid phase (capillary electrophoresis or liquid chromatography in reversed phase, ion chromatographic or size-exclusion mode) is particularly suitable since the available techniques cover a very wide range of analyte polarities and molecular mass. Moreover, derivatisation can normally be avoided in liquid-phase separation. Particularly in complex environmental or biological samples, separation in one dimension is not sufficient for obtaining adequate resolution for all relevant species. In this case, multi-dimensional separation, based on orthogonal separation techniques, has proven successful. ESI-MS is also often used in parallel with inductively coupled plasma MS detection. This review is structured in two parts. In the first, the fundamentals of atmospheric pressure ionisation techniques are briefly reviewed. The second part of the review discusses recent applications including redox species, use of ESI-MS for structural elucidation of metal complexes, characterisation and quantification of small organometallic species with relevance to environment, health and food. Particular attention is given to the characterisation of biomolecules and metalloproteins (metallothioneins and phytochelatins) and to the investigation of the interaction of metals and biomolecules. Particularly in the latter field, ESI-MS is the ideal technique due to the softness of the ionisation process which allows to assume that the detected gas-phase ions are a true representation of the ions or ion-biomolecule complexes prevalent in solution. It is particularly this field, important to biochemistry, physiology and medical chemistry, where we can expect significant developments also in the future.

Atmospheric Pressure↗
PubMed2003

Speciation of Pt(II) and Pt(IV) in spiked extracts from road dust using on-line liquid chromatography-inductively coupled plasma mass spectrometry.

The emission of platinum from automobile catalytic exhaust converters is well known and the accumulation of Pt in road dust has been studied by the analysis of total Pt contents. However, there are few studies on the speciation of the emitted Pt-compounds in the environment. A separation method with HPLC-UV has been developed by Nachtigall et al. [Chromatogr. A 775 (1997) 197] with aqueous standards of Pt(II)- and Pt(IV)-chloro complexes. Due to the limited selectivity and sensitivity of the UV-detection this method is not suitable for Pt-speciation in road dust extracts. Therefore, in this study the method of Nachtigall et al. was modified to realize an on-line coupling to ICP-MS with the advantage of Pt-specific detection. Calibration was performed with aqueous standards and spiked road dust extracts. Calibration curves were linear with low residual standard deviation (1.3-3.1% for the aqueous standards) and approximately 10-times lower detection limits compared to the HPLC-UV-method. Moreover, the stability of the model species was investigated using isocratic as well as gradient separation. Isotopic ratios of 194Pt, 195Pt, 196Pt and 198Pt were determined for quality control. A new mathematical correction method for the HfO-interference on the 195Pt-signal was developed. Additionally, the elution pattern of further elements in the road dust extracts was monitored and total element contents were determined in unspiked road dust extracts.

Calibration↗
PubMed1998

Application of capillary zone electrophoresis-inductively coupled plasma mass spectrometry and capillary isoelectric focusing-inductively coupled plasma mass spectrometry for selenium speciation.

The high resolution potential of capillary electrophoresis (CE) makes CE techniques valuable for separations of selenium species, both, organic and inorganic. Such effective separations of charged species are possible using the CZE mode (Z = zone). Very powerful separations can be achieved by capillary isoelectric focusing, when analysing molecules showing different isoelectric points (pI) values, such as organic Se species. Inductively coupled plasma (ICP) MS is an element-specific multi-element detector, providing extremely low detection limits. The combination of CE with ICP-MS promises a powerful tool for metal speciation. Therefore, an online hyphenation of CE [using capillary zone electrophoresis (CZE) or capillary isoelectric focusing (cITP) model] with ICP-MS, which was developed earlier, was modified and applied to selenium speciation. Separation was differentiated from the detection step during hyphenation. This resulted in short separation times (10 min) and a subsequent detection step lasting 100 s. Firstly, a CZE method was applied, providing a separation of six Se species of interest in one run [Se(IV), Se(VI), selenium carrying glutathione (GSSeSG), selenomethionine (SeM), selenocystine (SeC), selenocystamine (SeCM)]. This CZE method used an alkaline background electrolyte (Na2CO3/NaOH). The Se species were separated sufficiently from each other. Detection limits were calculated as 10 or 20 micrograms Se l-1 for inorganic Se species and 30-50 micrograms Se l-1 for organic Se species. The method was applied to standard mixtures and body fluids like human milk and serum. Secondly, a cIEF separation (pH range 2-10) was employed for organic Se species only in parallel. Detection limits were around 10-30 micrograms Se l-1. The method was applied to standard mixtures and body fluids like human milk and serum.

Electrophoresis, Capillary↗