Quantitative Speciation Research Articles

Evaluation of Quantitative Sulfur Speciation in Gas Oils by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry: Validation by Comprehensive Two-Dimensional Gas Chromatography

Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) has been applied for the quantitative speciation of sulfur containing compounds in gas oil (GO). For this purpose, ionization and mass spectrometric parameters have been studied and optimized with a set of standard compounds and GO samples. Comprehensive two-dimensional gas chromatography (GCxGC) was used as the reference method. To allow a quantitative comparison between FT-ICR MS and GCxGC results for GO samples, FT-ICR MS parameters were optimized and data obtained by both techniques were standardized. Response factors were established for two ionization modes: atmospheric pressure photo ionization (APPI) and electrospray after selective derivatization of sulfur compounds (MeESI). To test the validity of the developed MS methods, a third GO was analyzed and response factors were applied. Comparison with GCxGC results showed good agreement for sulfur families (deviation within 5% and 15% for MeESI and APPI data, respectively). Abundances of individual isomer groups match within 40% in most cases. These results principally demonstrate the suitability of FT-ICR MS for a quantitative analysis of sulfur compounds (by DBE and carbon number distribution pattern) in petroleum middle distillates. This approach has the potential to be extended to higher- and non-boiling petroleum fractions where quantitative speciation is presently not available.

Arsenic Speciation and Phytoavailability in Contaminated Soils Using a Sequential Extraction Procedure and XANES Spectroscopy

In this study, a sequential extraction procedure (SEP) and X-ray absorption near edge structure (XANES) spectroscopy were used to determine the solid-phase speciation and phytoavailability of arsenic (As) of historically contaminated soils from As containing pesticides and herbicides and soils spiked with As in the laboratory. Brassica juncea was grown in the contaminated soils to measure plant available As in a glasshouse experiment. Arsenic associated with amorphous Fe oxides was found to be the dominant phase using both SEP and XANES spectroscopy. Arsenic predominantly existed in arsenate (As(V)) form in the soils; in a few samples As was also present in arsenite (As(III)) form or in scorodite mineral. Arsenic concentration in shoots showed significant (p < 0.001-0.05) correlations with the exchangeable As (r = 0.85), and amorphous Fe oxides associated As evaluated by the SEP (r = 0.67), and As associated with amorphous Fe oxides as determined by XANES spectroscopy (r = 0.51). The results show that As in both fractions was readily available for plant uptake and may pose a potential risk to the environment. The combination of SEP and XANES spectroscopy allowed us the quantitative speciation of As in the contaminated soils and the identification of valence and mineral forms of As. Such detailed knowledge on As speciation and availability is vital for management and rehabilitation of As-contaminated soils.

Quantitative HPLC-ICP-MS analysis of antimonyredox speciation in complex sample matrices: new insights into the Sb-chemistry causing poor chromatographic recoveries

In solution antimony exists either in the pentavalent or trivalent oxidation state. As Sb(III) is more toxic than Sb(V), it is important to be able to perform a quantitative speciation analysis of Sb's oxidation state. The most commonly applied chromatographic methods used for this redox speciation analysis do, however, often show a low chromatographic Sb recovery when samples of environmental or biological origin are analysed. In this study we explored basal chemistry of antimony and found that formation of macromolecules, presumably oligomeric and polymeric Sb(V) species, is the primary cause of low chromatographic recoveries. A combination of HPLC-ICP-MS, AFFF-ICP-MS and spin-filtration was applied for analysis of model compounds and biological samples. Quantitative chromatographic Sb redox speciation analysis was possible by acidic hydrolysis of the antimony polymers prior to analysis. Sample treatment procedures were studied and the optimum solution was acidic hydrolysis by 1 M HCl in the presence of chelating ligands (EDTA, citrate), which stabilise the trivalent oxidation state of Sb.

Quantitative speciation of heavy metals in soil and crops of agricultural fields of Islamabad, Pakistan

Two root crops: carrot (Daucus carota) and spring onion (Allium fistulosum) and soil samples were selected from the agricultural fields located near Islamabad, Pakistan to determine their elemental content. Field soil speciation of the two crops was also carried out to analyse the correlation of the elements in field crop and soil. Concentrations of selected elements were evaluated in the leaf, stem, root and flowering part of the crops using flame atomic absorption spectrophotometry. The results showed that elements are mostly concentrated in soil rather than crop parts following the sequence Zn>Cu>Pb>Ni>Cr>Cd. Furthermore, soil speciation showed that Ni and Cr are more prevalent in the Fe–Mn oxide fraction, Zn and Cd as the carbonate bound fraction and Cu is found in the organic bound form. However, concentrations of Pb are similar across the carbonate, Fe–Mn oxide and organic bound fractions. The highest average concentration of Zn is found as the carbonate bound fraction (2.09 ± 0.005 mg kg−1) and Cu as the organic bound (1.51 ± 0.029 mg kg−1) in soil samples taken from the agricultural field of Daucus carota.

Global approach for the selection of high temperature comprehensive two-dimensional gas chromatography experimental conditions and quantitative analysis in regards to sulfur-containing compounds in heavy petroleum cuts

Extending the knowledge on sulfur-containing compounds is crucial for the petroleum industry because they contribute to atmospheric pollution by combustion. Most of them are concentrated in heavy petroleum cuts, such as vacuum gas oils (VGOs). However, the resolution of the existing analytical methods does not allow a quantitative speciation of S-compounds contained in VGOs. Therefore, a high temperature GC×GC chromatograph hyphenated to a SCD was implemented in this study to obtain a quantitative S-compounds speciation. Firstly, various thermally stable stationary phases, in particular the new ionic liquid IL59 and Mega Wax-HT, were investigated in 1D-GC as a way to reduce the number of columns sets to be used in GC×GC. Consequently, several normal and reversed configurations of these columns were selected and tested in GC×GC. Then, a decision method was applied to facilitate the choice of the best combination of columns. Finally, the most adapted methods led to an innovative group type quantification and to a quantitative distribution of heavy sulfur species contained in a VGO sample. These results represent a major step towards the study of S-compounds in heavy petroleum cuts.

Iron solid-phase differentiation along a redox gradient in basaltic soils

Iron compounds in soil are multifunctional, providing physical structure, ion sorption sites, catalytic reaction-centers, and a sink for respiratory electrons. Basaltic soils contain large quantities of iron that reside in different mineral and organic phases depending on their age and redox status. We investigated changes in soil iron concentration and its solid-phase speciation across a single-aged (400 ky) lava flow subjected to a gradient in precipitation (2200–4200 mm yr −1) and hence redox history. With increasing rainfall and decreasing Eh, total Fe decreased from about 25% to <1% of the soil mass. Quantitative speciation of soil solid-phase iron was constrained by combining 57Fe Mössbauer spectroscopy (MBS) at 295 and 4.2 K with powder X-ray diffraction, selective chemical extractions, and magnetic susceptibility measurements. This approach allowed us to partition iron into (1) nanoparticulate and microcrystalline Fe III-(oxy)hydroxides, (2) microcrystalline and bulk Fe III-oxides, (3) organic/silicate bound Fe III, and (4) ferrous iron. The Fe III-(oxy)hydroxide fraction dominated solid-phase Fe, exhibiting a crystallinity continuum based on magnetic ordering temperature. The continuum extended from well-ordered microcrystalline goethite through nanocrystalline Fe III-(oxy)hydroxides to a nano Fe III-(oxy)hydroxide phase of extremely low crystallinity. Magnetic susceptibility was correlated ( R 2 = 0.77) with Fe III-oxide concentration, consistent with a contribution of maghemite to the otherwise hematite dominated Fe-oxide fraction. The Fe III-(oxy)hydroxide fraction of total Fe decreased with increasing rainfall and was replaced by corresponding increase in the organic/silicate Fe III fraction. The crystallinity of the Fe III-(oxy)hydroxides also decreased with increasing rainfall and leaching, with the most disordered members of the crystallinity continuum, the nano Fe III-(oxy)hydroxides, gaining proportional abundance in the wetter sites. This finding runs counter to the conventional kinetic expectation of preferential removal of the most disordered minerals in a reductive dissolution-dominated environment. We suggest the persistence of highly disordered Fe phases reflects the dynamic redox conditions of these upland soils in which periods of anoxia are marked by high water-throughput and Fe 2+(aq) removal, while periodic Fe oxidation events occur in the presence of high concentrations of organic matter. Our 57Fe Mössbauer study shows basalt-derived nano-scale Fe III phases are more disordered than current synthetic analogs and have nano-structural characteristics that are linked to their formation environment.

A new method for the characterisation and quantitative speciation of base metal smelter stack particulates

Base metal smelters may be a source of particulates containing metals of environmental concern released to the atmosphere. Knowledge of the quantitative chemical speciation of particulate releases from base metal smelters will be of value in smelter emission fingerprinting, site-specific risk assessments, predictions of the behaviour of smelter stack particulates released to the environment and in resolving liability issues related to current and historic releases. Accordingly, we have developed an innovative approach comprising bulk chemical analysis, a leaching procedure, X-ray diffraction analysis and scanning electron microscopy/electron probe microanalysis characterisation in a step-wise apportioning procedure to derive the quantitative speciation of particulate samples from the stacks of three copper smelters designated as A, B and C. For the A smelter stack particulates, the major calculated percentages were 29 CuSO(4), 20 ZnSO(4).H(2)O, 13 (Cu(0.94)Zn(0.06))(2)(AsO(4))(OH), 11 PbSO(4) and four As(2)O(3). For the B smelter stack particulates, the primary calculated percentages were 20 ZnSO(4).H(2)O, 20 PbSO(4), 12 CuSO(4) and nine As(2)O(3). Finally, we calculated that the C smelter stack particulates mostly comprised 34 ZnSO(4).H(2)O, 19 (Cu(0.84)Zn(0.16))(AsO(3)OH), 11 PbSO(4), 10 As(2)O(3) and nine Zn(3)(AsO(4))(2). Between 56% and 67% by weight of the smelter stack particulates, including the As, was soluble in water. For these and other operations, the data and approach may be useful in estimating metals partitioning among water, soil and sediment, as well as predictions of the effects of the stack particulates released to the environment.

ChemInform Abstract: NEXAFS Spectromicroscopy of Polymers: Overview and Quantitative Analysis of Polyurethane Polymers

Abstract The successful application of X-ray spectromicroscopy to chemical analysis of polymers is reviewed and a detailed application to quantitative analysis of polyurethanes is presented. Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy is the basis of chemical sensitive X-ray imaging, as well as qualitative and quantitative micro-spectroscopy. These capabilities are demonstrated by a review of recent work, and by presentation of new results outlining a methodology for quantitative speciation of polyurethane polymers. C 1s inner-shell excitation spectra of a series of molecular and polymeric model compounds, recorded by gas phase inelastic electron scattering (ISEELS) and solid phase NEXAFS techniques, are used to understand the spectroscopic basis for chemical analysis of polyurethanes. These model species contain the aromatic urea, aromatic urethane (carbamate) and aliphatic ether functionalities that are the main constituents of polyurethane polymers. Ab initio calculations of several of the model molecular compounds are used to support spectral assignments and give insight into the origin and relative intensities of characteristic spectral features. The model polymer spectra provide reference standards for qualitative identification and quantitative analysis of polyurethane polymers. The chemical compositions of three polyurethane test polymers with systematic variation in urea/urethane content are measured using the spectra of model toluene diisocyanate (TDI) urea, TDI-carbamate, and poly(propylene oxide) polymers as reference standards.

Simultaneous speciation of arsenic (As(III), MMA, DMA, and As(V)) and selenium (Se(IV), Se(VI), and SeCN−) in petroleum refinery aqueous streams

High-performance liquid chromatography (HPLC) coupled to an ICP-MS with an octapole reaction system (ORS) has been used to carry out quantitative speciation of selenium (Se) and arsenic (As) in the stream waters of a refining process. The argon dimers interfering with the (78)Se and (80)Se isotopes were suppressed by pressurizing the octapole chamber with 3.1 mL min(-1) H(2) and 0.5 mL min(-1) He. Four arsenic species arsenite--As(III), arsenate (As(V)), monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA)--and three inorganic Se species--selenite Se(IV), selenate Se(VI), and selenocyanate (SeCN(-))--were separated in a single run by ion chromatography (IC) using gradient elution with 100 mmol L(-1) NH(4)NO(3), pH 8.5, adjusted by addition of NH(3), as eluent. Repeatabilities of peak position and of peak area evaluation were better than 1% and about 3%, respectively. Detection limits (as 3sigma of the baseline noise) were 81, 56, and 75 ng L(-1) for Se(IV), Se(VI), and SeCN(-), respectively, and 22, 19, 25, and 16 ng L(-1) for As(III), As(V), MMA, and DMA, respectively. Calibration curve R (2) values ranged between 0.996 and 0.999 for the arsenic and selenium species. Column recovery for ion chromatography was calculated to be 97 +/- 6% for combined arsenic species and 98 +/- 3% for combined selenium species. Because certified reference materials for As and Se speciation studies are still not commercially available, in order to check accuracy and precision the method was applied to certified reference materials, BCR 714, BCR 1714, and BCR 715 and to two different refinery samples--inlet and outlet wastewater. The method was successfully used to study the quantitative speciation of selenium and arsenic in petroleum refinery wastewaters.

Chemical Transformations during Aging of Zerovalent Iron Nanoparticles in the Presence of Common Groundwater Dissolved Constituents

Nanoscale zerovalent iron (NZVI) that was aged in simulated groundwater was evaluated for alterations in composition and speciation over 6 months to understand the possible transformations NZVI could undergo in natural waters. NZVI was exposed to 10 mN of various common groundwater anions (Cl(-), NO(3)(-), SO(4)(2-), HPO(4)(2-), and HCO(3)(-)) or to dissolved oxygen (saturated, approximately 9 mg/L). Fresh and exposed NZVI samples, along with Fe-oxide model compounds, were then analyzed using synchrotron radiation X-ray absorption spectroscopy (XAS) to yield both relative oxidation state, using the X-ray absorption near edge structure (XANES), and quantitative speciation information regarding the types and proportions of mineral species present, from analysis of the extended X-ray absorption fine structure (EXAFS). Over 1 month of aging the dissolved anions inhibited the oxidation of the NZVI to varying degrees. Aging for 6 months, however, resulted in average oxidation states that were similar to each other regardless of the anion used, except for nitrate. Nitrate passivated the NZVI surface such that even after 6 months of aging the particles retained nearly the same mineral and Fe(0) content as fresh NZVI. Linear least-squares combination fitting (LCF) of the EXAFS spectra for 1 month-aged samples indicated that the oxidized particles remain predominantly a binary phase system containing Fe(0) and Fe(3)O(4), while the 6 month aged samples contained additional mineral phases such as vivianite (Fe(3)(PO(4))(2).8H(2)O) and iron sulfate species, possibly schwertmannite (Fe(3+)(16)O(16)(OH,SO(4))(12-13).10-12H(2)O). The presence of these additional mineral species was confirmed using synchrotron-based X-ray diffraction (XRD). NZVI exposed to water saturated with dissolved oxygen showed a rapid (<24 h) loss of Fe(0) and evolved both magnetite and maghemite (gamma-Fe(2)O(3)) within the oxide layer. These findings have implications toward the eventual fate, transport, and toxicity of NZVI used for groundwater remediation.

Direct quantitative speciation of selenium in selenium-enriched yeast and yeast-based products by X-ray absorption spectroscopy confirmed by HPLC-ICP-MS

Selenium (Se)-enriched yeast has probably been the most widely investigated food supplement and the literature on Se speciation in the Se-enriched yeast is fairly abundant, however, the strategy for Se speciation commonly requires complicated pretreatment procedures such as digestion and stepwise extraction. The present study was carried out to apply X-ray absorption spectroscopy (XAS) for the direct speciation of Se species with minimal pretreatment steps. By comparison of the XAS spectra of Se-enriched yeast samples with that of the standard Se species, organic R–Se–R (represented by selenomethionine) was found to be the main chemical form of Se. Quantitative speciation through principal component analysis (PCA) and least-squares linear combination (LC) fitting the Se-enriched yeast samples found 83%, 85% and 81% of R–Se–R (probably selenomethionine which is known to exist in yeast) for SelenoPrecise® yeast, SelenoPrecise® tablets, and Xiweir® tablets, respectively, which is in agreement with those from HPLC-ICP-MS analysis. More broadly, XAS can also be applied to other Se-enriched products with the merit of minimal pretreatment. However since XAS, specifically XANES, can only identify the chemical type rather than specific molecules, other methods like HPLC-ICP-MS are necessary to give not only the coordination environment of Se but also the identity of the Se species.

Simultaneous determination of seven elemental species in estuarine waters by LC-ICP-DRC-MS

A new multi-elemental speciation method was developed for seven species of three elements namely As(III), As(VI), MMA, Cr(III), Cr(VI), Se(IV) and Se(VI), using liquid chromatography-inductively coupled plasma-mass spectrometry. The use of dynamic reaction cell technique in removing polyatomic interference dramatically extended the detection sensitivity for all seven species with methane as the reaction gas. The developed condition offered low detection limits in ranges of 0.12–0.44 μg L−1, 0.24–0.29 μg L−1 and 0.26 μg L−1 for species of As, Cr and Se, respectively. For concise quantitative speciation, a controlled chelation condition for Cr species was optimized to minimize species interconversion. In the developed method, the seven species were baseline-separated in an 11-minute elution on an anion exchange column using NH4NO3/NH4H2PO4 as the mobile phase at pH 6. This efficient, high-throughput and sensitive method was fully validated and applied in quantitative speciation of river water samples collected from the Shing Mun River of Hong Kong. Most of the species were found as the toxic forms of the elements studied.

Quantitative speciation of arsenic compounds when using organic solvent gradients in HPLC-ICPMS

Quantitative analysis with HPLC-ICPMS under gradient elution conditions with increasing content of organic solvents is severely restricted because the elemental response can vary significantly with the amount of carbon reaching the plasma. The present work offers a solution to this challenge to elemental species quantification by introducing a volatile organic solvent directly into the spray chamber whereby the sample introduction system is saturated with organic vapours and no change in sensitivity is observed during a methanol gradient separation. This gradient compensation method was tested with a newly developed chromatographic separation of 12 arsenic species comprising arsenite, arsenate, methylarsonate, dimethylarsinate, four oxo-arsenosugars and four thio-arsenosugars within a run of 25 min using a Hamilton PRP-X100 column applying a methanol gradient up to 50% (v/v). Under these conditions 10 of the 12 species could be separated, whereas arsenite and oxo-arsenosugar glycerol co-elute near the front. Species independent quantification was performed against dimethylarsinate as calibrant and the results were compared with isocratic quantifications. Without compensation arsenic species eluting with more methanol in the organic phase were overestimated by factors of 8 to 10, whereas with gradient compensation the results for all arsenic species were comparable with results obtained from isocratic separations. The method was applied to the determination of arsenosugars in the BCR 710 oyster tissue candidate reference material. Results from these experiments underline the applicability of the proposed gradient compensation method for species independent quantification under reversed phase conditions. The method enables accurate quantification without post column modification.

Enriched stable isotopes and isotope pattern deconvolution for quantitative speciation of endogenous and exogenous selenium in rat urine by HPLC-ICP-MS

Download options Please wait... Article information DOI https://doi.org/10.1039/B820297B Article type Paper Submitted 12 Nov 2008 Accepted 02 Feb 2009 First published 02 Mar 2009 Download Citation J. Anal. At. Spectrom., 2009,24, 460-468 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions Enriched stable isotopes and isotope pattern deconvolution for quantitative speciation of endogenous and exogenous selenium in rat urine by HPLC-ICP-MS H. González Iglesias, M. L. Fernández Sánchez, J. A. Rodríguez-Castrillón, J. I. García-Alonso, J. López Sastre and A. Sanz-Medel, J. Anal. At. Spectrom., 2009, 24, 460 DOI: 10.1039/B820297B To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Social activity Tweet Share Search articles by author H. González Iglesias M. L. Fernández Sánchez J. A. Rodríguez-Castrillón J. I. García-Alonso J. López Sastre A. Sanz-Medel

Quantification of selenium species in petroleum refinery wastewaters using ion chromatography coupled to post-column isotope dilution analysis ICP-MS

A post-column Isotope Dilution Analysis (IDA) methodology has been used to carry out the quantitative speciation of selenium (Se) in industrial wastewaters by ion chromatography coupled to ICP-MS with an octapole reaction system (ORS). The interfering argon dimers on the 78Se and 80Se isotopes were suppressed by pressurizing the octapole chamber with 4 mL min-1 of hydrogen. The inorganic Se species selenite [Se (IV)], selenate [Se (VI)] and selenocyanate [SeCN-] were separated by ion chromatography (IC) using isocratic elution with 20 mmol L-1 Na2CO3 / 2 mmol L-1 NaHCO3 as eluent. After the separation, the eluent carbonates were converted to CO2 on-line by a membrane self-regenerating suppressor, in order to avoid clogging problems in the nebulizer or in the cones of the ICP-MS interface. Detection limits (as 3σ of the baseline noise) of 0.18, 0.13 and 1.0 ng g-1 were achieved for Se (IV), Se (VI) and SeCN- respectively. Quantification of selenium in each separated species was performed using post-column isotope dilution analysis by continuous mixing of an enriched 77Se spike solution with the effluent from the suppressor column. Finally, the 78Se/77Se or 80Se/77Se isotope ratios were monitored and the concentration of the corresponding selenium species was evaluated. The proposed methodology has been successfully applied to study the quantitative speciation of selenium in petroleum refinery wastewaters.

Advantages and limitations of a desolvation system coupled online to HPLC-ICPqMS/ES-MS for the quantitative determination of sulfur and arsenic in arseno-peptide complexes

High sulfur detection limits, mainly caused by the interfering O2+ ions, made simultaneous sulfur and arsenic speciation analysis by on-line coupling of RP-HPLC with ES-MS and ICP-MS rather difficult in the past. The application of a desolvation system avoids the formation of the interfering ions in the first place. In this study the Aridus system was tested. The sulfur detection limit of the used ICP-qMS in its standard mode could be improved by a factor 2000 to 50 ng S g−1. But great care had to be taken regarding species independent quantification, the major advantage of ICP-MS, since the analyte transport of certain compounds such as methionine or arsenite to the ICP was affected by the desolvation system. However, sulfate was found to be a suitable calibrant for sulfur containing peptides such as phytochelatins. Hence, this method demonstrates for the first time, the potential to identify and quantify individual phytochelatins without phytochelatin standards. This is of importance, since no reliable and affordable phytochelatin standards are available, which would be necessary when molecular mass spectrometric methods would have been used solely. But a successful quantitative speciation analysis of free phytochelatins and their arsenite complexes was hampered due to peak broadening and more serious, the formation of arsenic-artefacts.

Study of the Effect of Sample Preparation and Cooking on the Selenium Speciation of Selenized Potatoes by HPLC with ICP-MS and Electrospray Ionization MS/MS

The efficiency of enzymatic hydrolysis and leaching with water using accelerated solvent extraction (ASE) or boiling was investigated for quantitative Se speciation in selenized potatoes using reversed phase HPLC coupled to ICP-MS. Preliminary identification of selenomethionine (SeMet), Se-methylselenocysteine (SeMeCys), and selenate in extracts of potato skin and flesh was achieved using complementary reversed phase and anion-exchange HPLC-ICP-MS and retention time matching with standards. The quantitative speciation data revealed a higher percentage of selenomethionine (73% of the total Se) found in the flesh in comparison with skin (containing 21% of the total Se as SeMet). ASE and boiling in water were found to be similar in terms of Se extraction efficiency and profiles. However, ASE was found to be more efficient than boiling with respect to sample cleanup and reduced sample handling. The presence of SeMet at parts per billion levels in selenized potatoes was confirmed by reversed phase HPLC with online ESI MS/MS.

HPLC−ICPMS and Stable Isotope-Labeled Approaches To Assess Quantitatively Ti(IV) Uptake by Transferrin in Human Blood Serum

Little is known about the effects of titanium found in patients wearing prostheses or about the biochemical pathways of this metal when used as an anticancer drug (e.g., titanocene dichloride). In this work, transferrin has been confirmed as the only carrier protein binding Ti in human blood serum samples by making use of different HPLC protein separations followed by element-specific Ti detection by ICPMS. Besides, isotope dilution analysis has been applied to the quantitative speciation of Ti-Tf in standards and human blood serum samples. Species-unspecific and species-specific isotope dilution modes have been explored. In the first case, very low Ti-Tf results were obtained even using two different chromatographic mechanisms, anion exchange (20-24%) and size exclusion (33-36%). Surprisingly, no major Ti species except Ti-Tf were observed in the chromatograms, suggesting that Ti(IV) hydrolysis and precipitation as inactive titanium oxide species could take place inside the chromatographic columns. These results demonstrate that chemical degradation of metalloproteins during analytical separations could ruin the sought speciation quantitative results. The isotope dilution species-specific mode, much more accurate in such cases, has been instrumental in demonstrating the possibility of gross errors in final metalloprotein quantification. For this purpose, an isotopically enriched standard of (49)Ti-Tf was synthesized and applied to the quantitative speciation of Ti-Tf again. Using this species-specific spike, Ti-Tf dissociation inside the chromatographic columns used could be corrected, and thus, quantitative Ti-Tf binding in serum (92-102%) was observed. In other words, the usefulness and potential of a species-specific isotope dilution analysis approach to investigate quantitatively metal-protein associations, which can be dissociated at certain experimental conditions, is demonstrated here for the first time.

Study on Quantitative Speciation, by BCR Method, of Zinc Content from River Sediments

The present work presents the results obtained during investigation of the zinc content of the water and river sediments in an area polluted by mining activities, to provide information on the mobility and availability of this element. Sediment and water samples have been collected from significant sites in a former mining area in which with some sterile pits, which represent a major environmental hazard.

Structural domains in peat as revealed by physical fractionation, sequential chemolysis and 15N and 13C CPMAS NMR spectroscopy

The distribution patterns of different C and N forms in peat seen using solid state 13C and 15N NMR spectroscopy were studied after applying a series of physical and chemical treatments. The material analysed includes four series of peat subfractions obtained by: (i) wet sieving, (ii) extraction with solvents specific for removing lipid or humic substances, (iii) mild degradation treatments yielding non-degraded residues (BF 3–MeOH transesterification, HI degradation, HCl hydrolysis) and (iv) thermal treatment. In particular the sample series (i) would inform on the influence of particle size in the quantitative speciation of C and N forms in the whole peat material, whereas series (ii) and (iii) should give further insight on the C and N distribution patterns upon the influence of classical reactions considered to selectively remove structural moieties of the peat organic matter, such are carbohydrate-derived, ester-linked alkyl and hydrolyzable peptidic structures. The NMR spectra suggested: (i) a lack of heterocyclic N forms in the coarsest peat granulometric fractions, and their highest concentration in fractions less than 100 μm in size; (ii) the preferential accumulation of heterocyclic N forms in the humic acid fraction isolated with a chelating extractant (Na 4P 2O 7); (iii) the survival of amide N forms after acid hydrolysis indicating that only a portion of the amide N forms were present in hydrolyzable form; (iv) the fact that heating of the peat was the treatment which most significantly increased the heterocyclic N moiety.