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Analytical and Bioanalytical Chemistry (v.363, #5-6)

First International Conference on Trace Element Speciation in Biomedical, Nutritional and Environmental Sciences by B. Michalke; Peter Schramel (pp. 429-430).

Speciation and legislation – Where are we today and what do we need for tomorrow? by T. Berg; Erik H. Larsen (pp. 431-434).

In international legislation concerning trace elements in food, in the environment or in occupational health most regulations are based on the total element contents, and are frequently given as maximum limits or guideline levels. In contrast, only few regulations pay attention to the molecular species in which the elements are bound. The international legislation concerning contaminants in food is presently being established in the Codex Alimentarius, which is an independent United Nations organisation under the joint FAO/WHO Food Standards Programme. Development of the Codex General Standard for Contaminants and Toxins in Food provides the framework for future international legislation on metals as contaminants in food. For certain food additives, which include some essential minerals, speciation is an integral part of the set of specification criteria, because only certain defined chemical compounds are permitted as sources of the essential element. The development of more species-specific analytical and toxicological data, and improved communication with legislators will be necessary before it will become possible to lay down species-specific regulations in all the cases where the specialised scientist will consider it reasonable.

Introduction to the EU-network on trace element speciation: preparing for the 21st century by R. Cornelis; C. Camara; L. Ebdon; L. Pitts; B. Welz; R. Morabito; O. Donard; H. Crews; E. H. Larsen; B. Neidhart; F. Ariese; E. Rosenberg; D. Mathé; G. M. Morrison; G. Cordier; F. Adams; P. Van Doren; J. Marshall; B. Stojanik; A. Ekvall; P. Quevauviller (pp. 435-438).

The main objective of the EU-network is to bring together scientists with a background in analytical chemistry interested in speciation method development with potential users from industry and representatives from legislative bodies. The network started on 1/10/1997 for a duration of 2 years. A series of meetings are being organised to debate all the important questions for collecting information on environmental, food and occupational health aspects of speciation and to define possible future projects. The findings and conclusions will be summarised as a series of general papers that will be published in the open literature, recapitulating the essential information gathered to date, outlining the state of the art for each topic and recommending legislative actions. A first meeting was held in Überlingen, Germany on 5–6 December 1997. The representatives from industry explained their interest in the network and the participants from the academic and national institutes gave a state-of-the-art presentation of their research. Out of this, a program was compiled for the following meeting in Segovia from 16 to 20 March 1998. The topics dealt with were: organotin compounds in the environmental session; the speciation and bioavailability of trace element species (Cr, Fe, Se), the quality of the data and new legislation in the food session; and identification of inhaled particles and the search for bioindicators for exposure to Ni and Pt in the occupational health/hygiene session. In each session about half of the participants came from industry. The delegates agreed on a list of priorities in speciation analysis. A www-page has been created: hhtp://www. speciation 21.plymouth.ac.uk. Everybody interested in adding information to the page is requested to mail this to lpitts@plymouth.ac.uk

Quality control and reference materials in speciation analysis by B. Michalke (pp. 439-445).

This contribution describes the need and some strategies for a rigid quality control in speciation analysis. Firstly, the term “chemical speciation” is defined and differentiated from experimental concepts now called “operationally defined speciation” or “functionally defined speciation”. The need for quality control in speciation is given by the big number of sources of errors during sampling, sample preparation, separation and detection. Errors such as stability problems, contaminations or losses, spectral interferences etc. are discussed. On the other hand, several concepts for problem solutions are described. One of these solutions is the use of certified reference materials (CRM). Unfortunately, species-certified CRM are only available for few matrices and few elements, e.g. mercury in fish or sediments, lead in solutions and urban dust etc. Therefore special quality control strategies are necessary for each part of the analytical speciation procedure. Several examples of such procedures are given and discussed.

Some sources of variability in application of the three-stage sequential extraction procedure recommended by BCR to industrially-contaminated soil by C. M. Davidson; P. C. S. Ferreira; Allan M. Ure (pp. 446-451).

Copper, lead, manganese and zinc have been determined in extracts of industrially-contaminated soil to investigate possible sources of variability in the three-stage sequential extraction procedure recommended by BCR. Analysis was performed by flame or electrothermal atomic absorption spectrometry, using reagent matched, multi-element standard solutions. Interferences were assessed by use of a single-point standard addition. Although the distribution of contaminants in the soil was expected to be heterogeneous, little difference in precision was found when replicate samples ranging in mass from 1–5 g were extracted, provided the extractant:soil ratio was kept constant. Significant differences in operational speciation were, however, obtained when the procedure was carried out independently by three different analysts. This may be due to the critical effect of pH in Step 2. Reproducibility was higher for air-dried than for field-moist soils, but larger amount of metals were extracted, suggesting alterations in speciation occurred during drying.

Capillary electrophoresis/electrospray ionization mass spectrometry (CE/ESI-MS) as a powerful tool for trace element speciation by O. Schramel; B. Michalke; A. Kettrup (pp. 452-455).

The on-line coupling of capillary electrophoresis (CE) and electrospray ionization mass spectrometry (ESI-MS) for speciation analysis is entailed with a number of difficulties due to technical and methodical reasons. The optimization of several parameters in order to provide stable operating conditions are illustrated in detail: the positioning of the CE capillary, the CE buffer system, the concentration sensitivity and the detection mode. Additionally, off-line ESI-MS investigations of metal species with different stabilities were carried out in order to assess the influence of the ESI-process on the analyzed samples. It turned out, that metal ions and weak metal complexes may undergo gas-phase ligand replacement and intramolecular charge transfer reactions. Therefore, the structure of species will be altered. Covalent organometallic compounds and strong metal complexes, on the other hand, will not be altered and will be detected as charged molecular ions and/or as charged ion-solvent clusters. Examples of different compounds illustrate this fact.

Capillary electrophoresis coupled to inductively coupled plasma mass spectrometry (CE/ICP-MS) and to electrospray ionization mass spectrometry (CE/ESI-MS): An approach for maximum species information in speciation of selenium by B. Michalke; O. Schramel; A. Kettrup (pp. 456-459).

On-line hyphenations consisting of a separation and a detection step are one of the most efficient techniques for identification and characterization of metal containing species. The high resolution power of capillary electrophoresis (CE) is used for the separation of three selenium species, whereas either electrospray ionization mass spectrometry (ESI-MS) or inductively coupled plasma mass spectrometry (ICP-MS) are taken for molecule or element specific detection.This work gives an overview about the possibilities and limitations, when using the two hyphenated systems for speciation investigations. In order to show the power of the two complementary techniques, a CZE method using 5% acetic acid as background electrolyte was applied to the separation of selenomethionine (SeM), selenocystine (SeC) and selenocystamine (SeCM).Depending on the species and the element, the detection limits of the CE/ICP-MS hyphenated system are up to 10² to 10³ times better than that for the CE/ESI-MS system.

Speciation of organotin in sediments by multicapillary gas chromatography with atomic emission detection after microwave-assisted leaching and solvent extraction-derivatization by Isaac Rodríguez Pereiro; A. Wasik; Ryszard Łobiński (pp. 460-465).

Microwave-assisted leaching of organotin compounds from sediment samples followed by the simultaneous extraction-derivatization of the extracted species was revisited with the goal to compare the existing procedures, improve their recoveries and extend them to phenyltin compounds. The stability of butyl- and phenyltin compounds under microwave field, real recoveries of the whole analytical procedure, effect of the extraction solvent, and the necessity for an internal standard were evaluated using two candidate reference sediments. The combination of the optimized sample preparation procedure with multicapillary chromatography resulted in a rapid (2 min leaching + 5 min extraction-derivatization + 3 min chromatographic separation) and efficient analytical procedure for speciation analysis of organotin compounds in sediment samples. The detection limit achieved with a microwave-induced plasma atomic emission detector was 2 ng g^–1.

Simultaneous determination of Hg(II) and alkylated Hg, Pb, and Sn species in human body fluids using SPME-GC/MS-MS by L. Dunemann; Hossein Hajimiragha; Jutta Begerow (pp. 466-468).

A GC/MS-MS method for the determination of Hg(II) and alkylated Hg, Pb, and Sn species in human urine is described. Separation and identification of the metal species are performed by capillary gas chromatography coupled with an ion-trap mass spectrometer with electron impact ionization in the tandem-MS mode. For sample preparation a very promising technique was applied that is based on a derivatization with sodium tetraethylborate followed by headspace solid phase microextraction (SPME). Operation of the used ion trap in the tandem-MS mode yields in improved detection limits because of a signal-to-noise ratio that is at least one order of magnitude better than in the MS mode. The detection limits in real matrices like urine are between 7 and 22 ng/L for all species investigated. Urinary levels of inorganic Hg in non-occupationally exposed persons with and without dental amalgam were found to be between 0.1 and 1.4 μg/L. A reference material (“ClinRep, Level I”) was used for quality assurance. Compared to the coupling of GC with ICP-MS (“inorganic” MS), the advantage of the proposed method using an “organic” MS is that (i) the species can be directly identified via their precursor and daughter ions and (ii) analysis can be performed with a commercially available hyphenated technique at moderate costs and needs no lab-made interfacing. Moreover, it offers a real multi-element/multi-species capability with low detection limits and a minimum of sample preparation.

Speciation of metal ions in proteins by combining PIXE and thin layer electrophoresis by Z. Szökefalvi-Nagy; C. Bagyinka; I. Demeter; K. Hollós-Nagy; I. Kovács (pp. 469-473).

Particle induced X-ray emission (PIXE) spectroscopy is a simple and convenient method of quantitative multielemental analysis with sensitivities in the μg/g range, that can be successfully used for trace analysis of metal ions in proteins or enzymes. However, due to its elemental character the technique alone is not a priori suitable for speciation. Keeping track of the metal ions of interest throughout a proper biochemical separation technique, on the other hand, could be a useful strategy for speciation. Different versions of thin layer electrophoresis (polyacrylamide gel, agarose or cellulose acetate electrophoresis) are very effective and sensitive methods to separate proteins or protein fragments. Due to the high absolute sensitivity of PIXE the metal ions concentrated in the narrow bands of an electropherogram can be in situ successfully detected. The present paper describes this unique combination of biochemical separation and ion beam analysis which significantly extends the information obtained from electrophoresis. Illustrative applications are given and the advantages and limitations of the method are discussed. Possible extensions of the technique are also outlined.

Effects of complexants and surfactants on the deposition and stripping steps in chronopotentiometric stripping analysis and anodic stripping voltammetry: implications for operationally defined speciation measurements by R. M. Town (pp. 474-476).

The influence of humic substances, Triton X-100 and red wine on the deposition and stripping steps in anodic stripping voltammetry and chronopotentiometric stripping analysis (CPSA) of Cu(II) and Pb(II) was investigated. Fulvic acid and Triton X-100 had an impact only on the stripping step; humic acid and red wine influenced both steps. Failure to establish the impact of matrix components on the individual deposition and stripping steps could result in erroneous interpretation of metal ion speciation.

Molecular activation analysis for chemical species studies by Chifang Chai; Xueying Mao; Yuqi Wang; Jingxin Sun; Qingfang Qian; Xiaolin Hou; Peiqun Zhang; Chunying Chen; Weiyu Feng; Wenjun Ding; Xiaolin Li; Chunsheng Li; Xiongxin Dai (pp. 477-480).

Molecular activation analysis (MAA) refers to an activation analysis method that is able to provide information on the chemical species of elements in systems of interest, though its exact definition has yet to be assigned. Its development is strongly stimulated by the urgent need to know the chemical species of elements, because knowledge of bulk contents or concentrations is often insufficient to judge biological, environmental or geochemical effects of elements. The features, methodology and limitations of MAA are outlined, as well as the up-to-date MAA progress in our laboratory.

Possibilities for the simultaneous preconcentration and flame atomic absorption spectrometric determination of Cr(III) and Cr(VI) using a C18 column and sorption loop by A. Gáspár; Csilla Sógor; József Posta (pp. 480-483).

The sorption loop as a preconcentration unit used so far in the low-pressure flow injection (FI) system was combined with the hydraulic high-pressure nebulizer (HHPN) and a high-pressure liquid chromatographic (HPLC) column. Thus, the sorption preconcentration of Cr(VI) can be coupled to a powerful sample introduction method or preconcentration techniques of Cr(III). The subsequent determination of the Cr(VI) content of the samples was carried out by flame atomic absorption (FAAS).

Development of native two-dimensional electrophoresis methods for the separation and detection of platinum carrying serum proteins: initial steps by S. Lustig; J. De Kimpe; R. Cornelis; P. Schramel (pp. 484-487).

The initial development steps of a native and powerful two-dimensional electrophoretic (2-D) method for the separation of platinum-proteins is described. Mild conditions were selected, particularly for the second dimension, e.g., avoiding buffer systems with platinophile N- or S-donor groups. Therefore, the separation reagents were checked if and at which concentration they can be used for this purpose. In the first dimension isoelectric focusing (IEF) was performed using immobilised pH gradients (IPGs). Native polyacrylamide gel electrophoresis (PAGE) was done in the second dimension. Detection of proteins was achieved via silverstaining. For the determination of platinum in the ultra-trace range, double focusing inductively coupled plasma mass spectrometry (HR-ICP-MS) was used. Autoradiography (¹⁹¹Pt tracer) will be done additionally in the future as a fast, powerful and elegant way of detecting the platinum carrying proteins after the second dimension.

Application of MIP-AES as element specific detector for speciation analysis by G. Heltai; T. Józsa; K. Percsich; I. Fekete; Z. Tarr (pp. 487-490).

An MIP-AES element specific detector has been directly coupled to an HPLC separation system by means of hydraulic high-pressure nebulization (HHPN) with an appropriate desolvation unit. This system was applied to Cr(III)/Cr(VI) speciation analysis. The linear dynamic range of Cr(III) and Cr(VI) determination was two orders of magnitude, absolute detection limits were 13 ng for Cr(III) and 18 ng for Cr (VI), respectively. The matrix effect caused by the easily ionizable elements (Na, Ca, K) was significant in real samples.

Evaluation of a commercially available microbore anion exchange column for chromium speciation with detection by ICP-mass spectrometry and hyphenation with microconcentric nebulization by S. Saverwyns; Karen Van Hecke; Frank Vanhaecke; L. Moens; Richard Dams (pp. 490-494).

The potential of a new commercially available microbore anion exchange column for chromium speciation (Cetac ANX-3202) was evaluated and its characteristics were studied. Nitric acid was used as mobile phase, making the technique ideal for coupling with inductively coupled plasma mass spectrometry (ICPMS). Because of the low operating flow rate of the column, a microconcentric nebulizer was used as an interface between the microbore column and the ICP-mass spectrometer. Co was added to the mobile phase and its signal intensity was continuously monitored and used as an internal standard to correct for signal drift and instrumental instability. Excellent results were obtained in terms of repeatability. Detection limits for Cr(III) and Cr(VI) are less than 1 μg · L^–1, using either ⁵²Cr or ⁵³Cr. The accuracy was determined by analyzing a certified reference material (BCR CRM 544). The concentrations found were in good agreement with those certified. The occurrence of C- and Cl-based molecular ions was studied and their influence on the determination of chromium was evaluated.

Flow injection electrochemical hydride generation atomic absorption spectrometry (FI-EHG-AAS) as a simple device for the speciation of inorganic arsenic and selenium by U. Pyell; A. Dworschak; F. Nitschke; B. Neidhart (pp. 495-498).

A flow-injection system for the determination of inorganic arsenic [As(III)/As(V)] and selenium species [Se(IV)/ Se(VI)] by electrochemical hydride generation, cryogenic trapping and atomic absorption spectrometry is described. A simple and robust electrochemical flow-through cell with fibrous carbon as cathodic material has been developed for the speciation of arsenic. A cold-trap system makes possible to eliminate interferences from methylated arsenic species. Without pre-reduction the system is selective to As(III) and Se(IV). The selectivity obtained with fibrous carbon as cathode material is compared to the selectivity obtained with a second electrochemical flow-through cell using a lead foil as cathode.

The role of element speciation in environmental and occupational medicine by Pietro Apostoli (pp. 499-504).

In order to evaluate the interaction with the environment or to assess absorption, binding mechanisms, reactivity and excretion of elements in humans, element speciation can provide more information than the analysis of element as a whole. Some examples that confirm the importance of speciation depend on the choice of the most appropriate indicator or representative matrix. The determination of As(III), As(V), monomethylarsonic and dimethylarsinic acids can be used to evaluate occupational exposure to As. Exposure to inorganic Hg should be measured by its content in urine, whereas in the case of exposure to alkyl Hg, blood and hair should be considered. Speciation may also be useful in studying element toxicokinetics, since it is well known that hexavalent Cr is taken up more than the trivalent form, and that species of the same metal are differently partitioned in blood. Pentavalent forms of As are absorbed more than trivalent forms, and the organic species of elements are excreted faster than inorganic species. In addition, speciation can play an important role in assessing element toxicodynamics. The toxicity of the three oxidation states of Hg differs considerably; for As a decreasing toxicity from arsenite to dimethylarsinic acid is proposed; for organotin compounds, higher toxicity for ethyl groups than for phenyl groups is reported. However, speciation in biological media is difficult when applied to other elements because of the lack of information on the existence and significance of species whose determination could be valuable. Furthermore, there may be no analytical methods that allow an accurate measurement of the species. The feasibility of speciation in occupational and environmental medicine depends mainly on our capability to solve some problems related to the identification and determination of species and on the demonstration that species measurement represents a clear improvement compared to total element determination.

Biomedical aspects of trace element speciation by Douglas M. Templeton (pp. 505-511).

Speciation affects the bioavailability and toxicity of elements and so is important in toxicology and nutrition. Exploitation of speciation profiles in medical management is widely unexplored. Isotopic speciation in the body can also offer clues to sources of exposure. The redox state of some elements determines toxicity and affects transport across biological barriers. Distinguishing inorganic from organometallic forms of Hg, Pb, and Sn is important to assess exposure to the more toxic organometallic species, whereas the organic forms of the metalloids As and Se reflect metabolism and detoxification. Special questions of speciation arise in therapeutic metal chelation and the use of metal-based drugs, contrast, and imaging agents. Essential elements in blood plasma are distributed among one or more macromolecular species, with generally a small low molecular mass fraction that is difficult to define because of the complex composition of the biological fluid, including amino and other organic acids, and thiols. Albumin and/or transferrin dominate the macromolecular species of many essential and non-essential elements.

Subcellular distribution of Al, Cu, Mg, Mn and other elements in the human liver by C. Chen; Peiqun Zhang; Xiangli Lu; Xiaolin Hou; Zhifang Chai (pp. 512-516).

The elemental concentrations and chemical species of Al, Br, Cl, Cu, K, Mg, Mn, Na and I in human liver and its subcellular fractions were studied by several biochemical techniques combined with neutron activation analysis. The highest concentrations of Al, Mg, and I were found in the nuclei, whereas those of Br, Cu, Cl, K, Mn and Na in the cytosol. About 20% of Br, half of Al and most of Cu (78.8%), Mg (65.9%) and Mn (80.6%) remained in the cellulose bags after dialysis of liver homogenate, which were suggested to be bound to macromolecules. K (100%) and more than 95% of Cl and Na were found to be in the dialyzates. Similar results were found in the fractions of nuclei, mitochondria, lysosome and microsome, respectively, after the same treatment. Further study was carried out to elucidate the elemental distribution in the cytosol by ethanol precipitation and by ammonium sulfate fractionation. The results suggested that several kinds of Cu-, Mn- and Mg-bound proteins existed in the cytosol of human liver cells.

Determination and distribution of human plasma selenoproteins by T. Plecko; S. Nordmann; M. Rükgauer; J. D. Kruse-Jarres (pp. 517-519).

Major portions of plasma-selenium are incorporated in the proteins glutathione peroxidase (GSH-Px), selenoprotein P (Sel P) and albumin. A chromatographic method, adapted from a procedure by Harrison et al. [6], uses heparin- and blue-sepharose to separate the three protein fractions. The determination of selenium was carried out by electrothermal atomic absorption spectroscopy (ETAAS) using the Zeeman effect. The selenium distribution of 17 healthy subjects was 68 ± 7% of the total plasma selenium associated to Sel P, 25 ± 4% associated to p-GSH-Px and 7±4% associated to albumin. The recovery of selenium was 99 ± 4%. For precision measurements a plasma pool has been separated seven times. The selectivity of this method was monitored by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and GSH-Px activity measurements. A fast method, adapted for clinical applications, is described which allows to determine the human plasma selenium distribution in about an hour.

Stability of vanadium(V)-protein complexes during chromatography by K. De Cremer; J. De Kimpe; R. Cornelis (pp. 519-522).

In order to reduce the risk of having artifacts during the separation of different vanadium containing proteins with chromatographic methods, we carried out some stability tests for selecting the most appropriate eluting conditions without breaking the vanadium(V)-protein binding. Therefore we investigated the stability of the vanadium-protein (transferrin and albumin) binding as function of the pH, salt molarity (NaCl, Na-acetate, NaBr, NaI, LiCl, NH₄Cl and CaCl₂) and hydrophobicity (acetonitrile). This was performed with a 48-vanadium tracer by means of batch experiments using ultrafiltration techniques to achieve a separation between protein bound and ‘free’ vanadium. We found that there was a significant pH-dependence. Depending on the eluting salt used, the vanadium(V)-protein binding is also disrupted by a high salt concentration (> 0.3 mol/L). An acetonitrile concentration around 2 mol/L has the same disrupting effect.

Rapid analysis for cadmium metallothionein complexes by HPLC using microparticulate stationary phases by Hubert Chassaigne; R. Łobiński (pp. 522-525).

Different columns with microparticulate (1.5 and 2 μm) stationary phases were investigated for the analysis of the polymorphism of mammalian metallothionein (MT) by reversed-phase HPLC. When a non-porous 1.5 μm stationary phase was used, the duration of the chromatographic run was reduced 10-fold (in comparison with the conventional 5 μm packing) without any loss in resolution. The method was applied to the analysis of MT-1 and MT-2 preparations from rabbit liver.

Determination of arsenic species in human urine using HPLC with on-line photooxidation or microwave-assisted oxidation combined with flow-injection HG-AAS by R. Sur; J. Begerow; L. Dunemann (pp. 526-530).

An improved analytical procedure is presented for the separation and simultaneous determination of hydride-forming (toxic) and not hydride-forming (non-toxic) arsenic species in human urine. Separation was performed by cation-exchange chromatography using a new solid phase type based on the continuous bed chromatography (CBC) technology. This column permits by a factor of 4 higher flow rates than conventional columns resulting in a drastical reduction of retention times without any loss of resolution. Using this type of column, arsenobetaine (AsBet), arsenocholine (AsChol), and dimethylarsinic acid (DMA) were separated from the more toxic arsenic species arsenous acid (As(III)), arsenic acid (As(V)), and methylarsonic acid (MA) within only 4 min. The HPLC system was coupled via a flow injection system and either a UV or a microwave (MW) reactor to the HG-AAS instrument. UV photolysis and MW digestion were used to transform AsBet and AsChol to hydride-forming species and to make them accessible to HG-AAS. UV photolysis turned out to be more suitable for this application than MW digestion, because the latter technique led to peak broadening and poorer performance. The described procedure was applied to the determination of arsenic species in urine samples of non-occupationally exposed persons before and 12 h after seafood consumption. Detection limits were about 1 μg/L for each arsenic species. After consumption, the AsBet and DMA excretion increased by at least a factor of 150 for AsBet and by a factor of 6 for DMA, respectively, while the excretion of the other species did not increase significantly. This invalidates the use of total urinary arsenic as well as total hydride-forming arsenic as an indicator for exposure to inorganic arsenic.

Strong organic ligands in marine organisms by K. Hirose; E. Tanoue (pp. 531-533).

The interaction between thorium and marine organisms (cultured bacterium, natural phytoplankton and zooplankton) was experimentally examined by using chemical equilibrium techniques. Thorium quantitatively reacts with the binding sites of bacterium (Shewanella algae), phytoplankton (mainly diatoms) and zooplankton (mainly copepods) in 0.1 M HCl solution. According to mass balance analysis of experimental adsorption data, thorium forms an 1 : 1 complex with the binding site in all marine organisms studied. Their stability constants are in the range of 10^6.59 and 10^6.74 M^–1 in an 0.1 M HCl solution. The mole ratio of ligand to organic carbon in the marine organisms ranged from 0.23 to 4.2 mmol/mol C; the ligand : carbon ratio in bacteria was more than one order of magnitude higher than that in phytoplankton and zooplankton. This result leads to the hypothesis that the strong organic ligand specified by Th is one of the essential functional groups in oceanic microorganisms.

Fractionation of chromium(III) compounds in biological matrices by A. Knöchel; Gundolf Weseloh (pp. 533-535).

Many details of the metabolism and biological significance of trivalent inorganic cations have remained obscure up to now, not least because of the lack of appropriate tools for species analysis of these cations in biological matrices. In order to demonstrate the capabilities of reversed-phase ion-pair chromatography, the distribution of chromium species in brewer’s yeast, previously incubated with radiolabelled ⁵¹Cr chloride was investigated. Contradictory to the findings of most other researchers in this area, two low-molecular weight, anionic chromium species were detected in cytosolic yeast extracts. In conclusion, reversed-phase ion-pair chromatography may reveal new details of intracellular metabolism of chromium(III) and, possibly, other trivalent cations.

The importance of trace element speciation in nutritional sciences by Susan J. Fairweather-Tait (pp. 536-540).

The importance of trace element speciation in relation to absorption and metabolism is reviewed. Availability for absorption depends upon the chemical form that is presented to the intestinal mucosal cells, namely solubility, oxidation state and the binding strength of ligands in the lumen of the gastrointestinal tract. For some elements, such as selenium, retention and utilisation appear to depend upon chemical form. The need to take speciation into consideration when undertaking trace element bioavailability studies employing isotopic labels is discussed.

Bioavailability of silicon from food and food supplements by K. Van Dyck; R. Van Cauwenbergh; Harry Robberecht; Hendrik Deelstra (pp. 541-544).

The bioavailability of silicon from three different silicon sources was studied. A diet rich in silicon, a tablet containing a dry extract of horsetail and a solution of silicon in a choline-glycerol matrix were compared. Blood and urine of one healthy test person were sampled to monitor the silicon uptake. The silicon content of blood and serum samples was determined by graphite furnace atomic absorption spectrometry. Strongly diverging results were obtained for the three different silicon sources. Neither an increase in urinary silicon excretion nor in serum silicon content was observed when feeding the silicon rich diet. Urinary silicon excretion did significantly (P < 0.05) rise during supplementation with tablets containing dry extract of horsetail. Intake of a solution of silicon in a choline-glycerol matrix resulted in a significantly (P < 0.05) increased urinary silicon excretion and serum silicon content. From these results it can be concluded that speciation (chemical form, matrix) strongly influences the bioavailability of silicon.

Study of minerals and trace element species in soybean flour by Hana Fingerová; R. Koplík (pp. 545-549).

The total concentrations of Na, Mg, P, K, Ca, Mn, Fe, Co, Ni, Cu, Zn, Se and Mo in soybean flour and in extract of soybean flour were determined by ICP – AES and ICP – MS. The highest element extractability was found in case of potassium (66 ± 7%) and nickel (66 ± 7%). The soybean flour extract was submitted to fractionation by size exclusion chromatography on a Fractogel EMD Bio SEC (S) column with 0.2 mol/L Tris-HNO₃ buffer pH 7.5. Sixty 2 mL fractions of effluent were collected and contents of elements were determined by ICP-MS and ICP-AES. Iron and selenium were predominantly present in fractions corresponding to molecular weight 380 kDa, while cobalt, nickel, copper, zinc and molybdenum were mostly found in low-molecular fractions (2–3 kDa). Most of phosphorus was found in the 7 kDa fraction. Sodium and potassium were present in fractions corresponding to molecular weights < 1 kDa.

Speciation in the environmental field – trends in Analytical Chemistry by Joanna Szpunar; Ryszard Łobiński (pp. 550-557).

The need for speciation-related information in environmental chemistry is critically evaluated. Recent advances in the analysis for volatile or volatizable organometallic compounds and redox states are presented. They include microwave-assisted extraction for the leaching of analytes and the solubilization of tissues, multicapillary gas chromatography, and integration of the sample preparation and separation steps in a single speciation-dedicated instrument. Particular attention is given to the needs for speciation analysis in environmental biota: plant and animal tissues. The areas discussed include speciation of selenium and arsenic, analytical chemistry of metal complexes with phytochelatins and metallothioneins, the need for the identification of metal enzymes and co-enzymes and their role in the biosynthesis of metal complexes. The status of the rapidly emerging field of bioinorganic analytical chemistry is discussed.

Influence of the addition of organic wastes on the metal contents of a soil by E. Díaz-Barrientos; L. Madrid; I. Cardo (pp. 558-561).

A 3-step sequential extraction scheme for soil metals was used to detect possible changes in the composition of metal species caused by several composted residues added to soils: urban solid residues (USR), waste from paper industry (WPI), and residues of olive oil industry (OI). In the first two fractions of the extraction process (soluble in weakly acid solutions and reducible) changes by USR and/or WPI can be observed, while the oxidisable fraction is much less affected. The data suggest a definite mobilisation of Zn by USR, but in general the increase is caused by the contribution of the metals originally present in the composts. OI is the least effective in altering metal species.

The nature of corrosion products in lead pipes used to supply drinking water to the City of Glasgow, Scotland, UK by Nicola J. Peters; C. M. Davidson; Andrew Britton; Stuart J. Robertson (pp. 562-565).

Corrosion products, obtained from lead service pipes carrying the public drinking water supply to the Glasgow area, have been characterised by FTIR spectrometry, powder x-ray diffraction spectrometry, flame atomic absorption spectrometry and ion chromatography. As expected, the products which formed in the presence of pH adjusted-water were mainly lead carbonate or basic lead carbonate. Products from areas where the water supply had been treated with orthophosphoric acid and pH adjustment for up to eight years also contained a variable proportion (up to ∼30% w/w) of a phosphate species. This has been identified as an apatite, most probably lead hydroxyapatite, Pb₅(PO₄)₃OH.

A field aluminium speciation method to study the aluminium hazard in water by D. Bérubé; Denis G. Brûlé (pp. 566-570).

The toxicity of aluminium is governed by its bioavailability. Therefore, the speciation of aluminium in drinking water becomes of prime importance to understand its fate and the population exposure, and to develop guidelines for the concentration levels. At Health Canada, a field speciation method has been developed to perform on-site speciation followed by measurement of Al in the laboratory. The following species are generated: 1) total recoverable; 2) total acid-leacheable; 3) total dissolved; 4) dissolved extracted; and 5) dissolved non extracted. The field extractions are performed by percolation through chelation columns, which are later processed in the laboratory. Aluminium determinations can then be performed by numerous methods, such as by Inductively Coupled Plasma Mass Spectrometry (ICPMS), Graphite Furnace Atomic Absorption Spectrometry (GFAAS) or Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES). Examples of results for raw or treated/ distributed surface waters, as well as for groundwaters, are used to illustrate the validity of the method, and the importance of considering aluminium speciation in characterizing the aluminium hazard in water.

Subspeciation of sulfidic nickel in particulates. Determination of Ni3S2, NiS2, and NiS in reference and fly ash samples by carbon paste electrode voltammetry by J. L. Wong; Anhua Liu; M. Tian; Wenrui Jin (pp. 571-572).

Nickel speciation of fly ash by sequential extraction lacks specific identification of the chemical forms in the sulfidic nickel phase. A new voltammetric analysis of Ni₃S₂, NiS, and NiS₂ in a carbon paste electrode is reported. Characteristic peaks were observed in acetate (pH 5) as the electrolyte; the anodic peak for Ni₃S₂ gave a linear dose response with microgram sensitivity. Reference compounds included heazlewoodite, millerite, commercial Ni₃S₂, NiS₂, and NiS, but the latter was shown to be mainly the subsulfide. No Ni₃S₂ was found in two types of laboratory generated ash: an oil ash containing mainly soluble nickel and a high sulfur petroleum coke ash enriched with nickel.

Determination of inorganic arsenic(III) in ground water using hydride generation coupled to ICP-AES (HG-ICP-AES) under variable sodium boron hydride (NaBH4) concentrations by Johannes Müller (pp. 572-576).

The determination of inorganic arsenic species in ground water matrices using hydride generation coupled online to ICP-AES (HG-ICP-AES) is suggested on the fact that the As(III)-species shows significantly higher signal intensities at low sodium boron hydride (NaBH₄) concentrations than the As(V)-species. The sodium boron hydride concentration used for the determination of As(III) without any considerable interferences of As(V) was at 13.2 mmol/L NaBH₄ (0.05 wt/v%), whereas the concentration for the total As determination was at 158.4 mmol/L NaBH₄ (0.6 wt/v%). The interferences of As(V) during the As(III) measurements were very small: at concentrations below 100 μg/L of total arsenic, the interferences of As(V) were smaller than 2%. An amount of As(III) higher than 10% of the total As amount could be determined exactly and reliably. The total amount of arsenic is measured after reducing the sample with 20 mmol/L L-cysteine (C₃H₇NO₂S). Finally, the amount of the As(V)-species is calculated by the difference between the As(III)-species and the total arsenic. Therefore, this analytical method requires the absence of organic arsenic species, but if they still appear, they could be frozen out with liquid nitrogen after the hydride generation system. The linearity of calibration reaches from 2 μg/L up to 1000 μg/L with a detection limit routinely of about 1 μg/L for each species. The advantages of this method in comparison to AAS measurements are the higher extent of the linear calibration range (3 orders of magnitude) and a higher sensitivity. Additional merits of the method developed are easy handling and high sampling rates.

Separation of organic and inorganic arsenic species by HPLC-ICP-MS by Susan Londesborough; J. Mattusch; Rainer Wennrich (pp. 577-581).

The HPLC separation of eight anionic, cationic or neutral arsenic species (arsenite, arsenate, monomethylarsonic acid, dimethylarsinic acid, arsenobetaine, arsenocholine, trimethylarsine oxide and tetramethylarsonium ion) on a high-capacity, anion-exchange column (Ion Pac AS 7, Dionex) was studied. The separation was performed during one run with a nitric acid gradient ranging from pH 4–1.3. The influence of sodium dodecyl sulfate (SDS), sodium octyl sulfate (SOS) and 1,2-benzenedisulfonic acid (BDSA) as ion pairing eluent modifiers was investigated. In addition the effect of elevated temperatures (30 to 40 °C) was studied. The best results were obtained at room temperature of 20 °C with 0.05 mM benzenedisulfonic acid as the eluent modifier. The chromatograph was connected to an ICP-MS via a cross-flow nebulizer. Detection limits obtained with the optimized chromatographic separation were 0.16–0.60 μg As L^–1 for different species. The proposed speciation method was applied to the determination of arsenic species in the DORM-2 reference material (Dogfish Muscle) and in aqueous extracts of mushrooms collected on arsenic contaminated ground.

A preliminary investigation of the operational and isotopic speciation of uranium in sediments by Susan E. Howe; C. M. Davidson; Martin McCartney (pp. 582-584).

Uranium was determined in extracts of inter-tidal sediment, obtained from a contaminated harbour, using the three-stage sequential extraction procedure recommended by BCR. The element was found mainly in association with reducible, or reducible and oxidisable, phases and the overall concentration was enhanced (up to 6.7 μg g^–1 dry weight) with respect to typical, UK levels. The ²³⁸U/²³⁵U ratio has been measured in digests of stream sediments obtained from the vicinity of a uranium enrichment plant. Significant enhancement in ²³⁵U with respect to the natural ²³⁸U/²³⁵U ratio (137.88:1) was observed at some locations.

Vertical distribution and potential sources of strong ligands for copper(II) in the North Pacific by T. Midorikawa; Eiichiro Tanoue (pp. 584-586).

Complexing ability of natural organic ligands in seawater was determined by an approach based on coordination chemistry, i.e., thermodynamic calculations of the conditional stability constants of remarkably stable copper(II) complexes of natural ligands, which were maintained against the ligand-exchange reaction with a large excess of ethylenediaminetetraacetic acid. There exist strong ligands with the conditional stability constant of log K’_CuL > 14 at pH 5.71 and 4° C ubiquitously in non-living dissolved organic matter, concentrated from both coastal and oceanic regimes. This type of ligand was detected at most depths from surface to 1,000 m in the oceanic regimes. The same appraoch was applied to a sample of marine organism (phytoplankton) and the strong ligand class was found out in phytoplankton. It is suggested that phytoplankton may be one of potential sources for the strong ligand.

Environmental mobility of trace metals in sediments collected in the Lake Balaton by Klára Polyák; József Hlavay (pp. 587-593).

In environmental pollution studies on solid materials sequential extraction techniques are used for the identification of the main binding sites of trace metals. A four-step sequential extraction procedure was applied to the determination of the distribution of elements like Cd, Cu, As, Pb, Cr, Ni, Zn, Al, Fe, and Mn in sediment samples collected in the Lake Balaton. The fractions were (1) exchangeable and bound to carbonate, (2) bound to Fe/Mn oxide, (3) bound to organic matter and sulfides, and (4) acid-soluble. Elements were mainly accumulated in the stable, acid-soluble fractions. Arsenic and Cd-ions were found in low concentration (1.2–13 mg/kg and < 1 mg/kg, respectively) in the samples. Based on the results determined at 15 sampling points it can be stated that the Lake Balaton has not yet been polluted by the elements investigated.

The sequential analytical procedure as a tool for evaluation of As, Cd and Zn mobility in soil by Jiřina Száková; Pavel Tlustoš; Jiří Balík; Daniela Pavlíková; Václav Vaněk (pp. 594-595).

The BCR EUR 14763 EN sequential extraction method, developed for the analysis of heavy metals in sediments, was applied to 35 soil samples covering the area of the Czech Republic. The soils varied in their physical-chemical properties and total element contents. While the residual fraction in the case of cadmium was only 18% of total Cd, for Zn and As the residual fraction was dominant (55 and 75%, respectively). The decreasing concentrations of extractable elements in the order Cd > Zn > As correspond to their availability in plants. The influence of selected soil properties (pH, sorption capacity, organic matter, and clay-silt-sand content) on the distribution of As, Cd and Zn was evaluated.

Copper speciation in aqueous solutions of fulvic acid and related molecular weight distributions by M. Wolf; G. Teichmann; E. Hoque; W. Szymczak; W. Schimmack (pp. 596-599).

Potentiometric and fluorescence measurements of aqueous solutions of fulvic acid containing Cu(NO₃)₂ or Cu(ClO₄)₂, respectively, were carried out at 25 °C and pH 5.5 to determine naturally occurring Cu species. The fulvic acid used was isolated by XAD-8 from filtrated (0.3 μm) water of a peat bog in the Dachauer Moos near Munich. From the results an operational molecular weight of fulvic acid of about 750 g/ mol was estimated, which was confirmed by molecular weight distributions determined by high-performance size-exclusion chromatography (HPSEC), gel permeation chromatography (GPC) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). Using this molecular weight and assuming that mainly 1:1 Cu-fulvic acid complexes are formed, a conditional stability constant of the Cu-fulvic acid complex of 10^5.9 could be calculated. These data are essential for the assessment of organic carrier-mediated migration of Cu as well as of the toxicological risk potential of Cu in aqueous environment and can be used as input parameters for geochemical modeling of the Cu species distribution in aqueous solutions.

Trace metal speciation in European River waters by Susan E. J. Buykx; R. F. M. J. Cleven; Anita A. Hoegee-Wehmann; M. A. G. T. van den Hoop (pp. 599-602).

Within an EC-study of the relationship between the chemistry of the aquatic system and resulting toxicological effects of heavy metals on micro-organisms, the speciation of trace metals is being assessed. The set-up of a speciation scheme is described, in which surface water is characterised in terms of total metal concentrations, nutrients, general parameters like DOC, pH and conductivity, metal binding properties and in which biologically relevant metal fractions are determined.

Chemical speciation study of platinum metals and other siderophile elements in Precambrian/Cambrian black shale, south China by C. Li; Chifang Chai; Xueying Mao; Hong Ouyang (pp. 602-605).

Chemical speciation of platinum metals and some other siderophile elements in Precambrian/Cambrian black shale, south China, were studied using stepwise dissolution, fire assay preconcentration, inductively coupled plasma mass spectrometry and instrumental neutron activation analysis. The results indicate that platinum metals in Precambrian/Cambrian black shale, south China, are enriched through a syngenetical mineralizing process.

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Analytical and Bioanalytical Chemistry (v.363, #5-6)