The high diversity of arsenolipids in herring fillet (Clupea harengus).

Arsenolipids represent a relevant step in the biosynthesis of organoarsenicals from inorganic arsenic compounds. Their fate after human consumption is still uncertain. By means of a HPLC-ICP-MS/ESI-Q-TOF-MS method, 16 lipid soluble arsenic compounds, including seven formerly unknown organoarsenicals, have been identified in commercial herring fillet. The structural assignment was done by exact mass and high resolution MS/MS data. This is the first identification of arsenolipids in herring (Clupea harengus). They contribute with (3.6±0.2) mg kg(-1) arsenic to 62.3% of the total arsenic content of (5.7±0.3) mg of arsenic per kg dry mass. Current studies indicate that a metabolization by humans to cancerous dimethylarsinic acid is very likely. The presented results are highly relevant as herring is a very popular food fish species in Europe. Moreover, the screening of different fish species revealed that arsenolipids are more widespread than previously assumed.

Impact of arsenic on uptake and bio-accumulation of antimony by arsenic hyperaccumulator Pteris vittata.

Individual uptake of As and Sb species in Pteris vittata have been investigated, but little information is available how uptake is affected if both metalloids are simultaneously present in different amounts. We investigated the uptake of antimony and its speciation in Pteris vittata cultivated in quartz substrate with, versus without, co-contamination with arsenic and a contaminated soil for 7 weeks. Applying HPLC-ICP-MS technique Sb(V), Sb(III), As(III), and As(V) could be identified as main species in aqueous extracts of roots and fronds with up to 230 mg kg(-1) of total Sb in the roots. Adding increasing amounts of As to the quartz substrate resulted in increasing uptake of Sb. In contrast to As, which is readily transferred to the fronds, Sb is primarily accumulated in the roots with Sb(V) being the dominant species (>90% of Sb). The addition of As doesn't result in enhanced translocation of Sb into the fronds.

In situ and ex situ study of the enhanced modification with iron of clinoptilolite-rich zeolitic tuff for arsenic sorption from aqueous solutions.

Adsorption methods have been developed for the removal of arsenic from solution motivated by the adverse health effects of this naturally occurring element. Iron exchanged natural zeolites are promising materials for this application. In this study we introduced iron species into a clinoptilolite-rich zeolitic tuff by the liquid exchange method using different organic and inorganic iron salts after pretreatment with NaCl and quantified the iron content in all trials by XRF spectroscopy. The materials were characterized by XRD, FTIR, FTIR-DR, UV-vis, cyclic voltammetry, ESR and Mössbauer spectroscopies before and after adsorption of arsenite and arsenate. The reached iron load in the sample T+Fe was %Fe(2)O(3)-2.462, n(Fe)/n(Al)=0.19, n(Si)/n(Fe)=30.9 using FeCl(3), whereby the iron leachability was 0.1-0.2%. The introduced iron corresponded to four coordinated species with tetrahedral geometry, primarily low spin ferric iron adsorbing almost 12 mug g(-1) arsenite (99% removal) from a 360 mug(As(III)) L(-1) and 6 mug g(-1) arsenate from a 230 mug(As(V)) L(-1). Adsorption of arsenite and arsenate reached practically a plateau at n(Fe)/n(Si)=0.1 in the series of exchanged tuffs. The oxidation of arsenite to arsenate in the solution in contact with iron modified tuff during adsorption was observed by speciation. The reduction of ferric iron to ferrous iron could be detected in the electrochemical system comprising an iron-clinoptilolite impregnated electrode and was not observed in the dried tuff after adsorption.

Analytical investigations of phenyl arsenicals in groundwater.

Phenylic arsenic compounds are the main contaminants in groundwater at abandoned sites with a history of arsenic containing chemical warfare agents (CWA). A fast and sensitive HPLC-ICP-MS method was developed to determine inorganic arsenic compounds like arsenite and arsenate as well as the degradation products of the arsenic containing warfare agents (phenylarsonic acid, phenylarsine oxide, diphenylarsinic acid). Beside these arsenic species the groundwater samples contained also high iron contents (up to 23 mg/l as Fe(II)) which led to precipitates in the samples after coming into contact with the atmosphere. Preservation immediately after sampling by phosphoric acid has shown that a successful avoidance of any losses of any arsenic species between sampling and analysis was possible. The suggested analytical method was applied to groundwater samples taken from different depths at a polluted site. The main contaminant in the water samples was diphenylarsinic acid (up to 2.1 mg/l) identified by ESI-MS, but also elevated concentrations of inorganic arsenic (up to 240 microg/l) were found.

Chemically modified maize cobs waste with enhanced adsorption properties upon methyl orange and arsenic.

The surface chemistry of maize naturasorbent was altered in this work by the modifying agents: phosphoric acid and different amines (triethanolamine, diethylenetriamine and 1,4-diaminobutane). Removal of methyl orange (25 mg l(-1)) was <50% by maize corn cobs modified by phosphorylation and higher by the quaternized samples: 68% with the 1,4-diaminobutane and 73% with the diethylenetriamine modificators. Adsorption of arsenite by the samples modified with phosphoric acid/ammonia was 11 microg g(-1), which corresponds to 98% removal from a 550 microg As l(-1) solution for an adsorbent dose of 50 mg ml(-1). The samples modified by phosphoric acid/urea removed 0.4 microg g(-1) arsenate from a 300 mug As l(-1) solution. Adsorption of methyl orange, arsenite and arsenate was superior by the chemically modified maize cobs judged against the initial naturasorbent. For comparison, removal by the commercial anion exchanger was 100% for methyl orange, 45% (5 microg g(-1)) for arsenite and 99% (5 microg g(-1)) for arsenate.

Preservation of arsenic species in water samples using phosphoric acid--limitations and long-term stability.

The preservation of arsenic species in water samples is an indispensable method to avoid their changes during storage, if it is not possible to analyse them immediately. The aim of this investigation was to demonstrate the limitations of the suggested method by using phosphoric acid as a preservation agent. The samples remain stable for 3 months, even if they show evidence of high concentrations of iron or manganese. Critical is an increasing pH>3. Theoretically, a precipitation of strengite (Fe(3)(PO(4))(2)) could occur, which should be avoided. Phosphoric acid with a final concentration of 10mM is recommended as a preservation agent, combined with keeping the samples cool (6 degrees C) and dark. Filtration of samples before preservation may be carried out with respect to the analytical aim to distinguish between the total and soluble fraction (without colloids). It was shown that filtered and non-filtered samples can be preserved by utilising the above mentioned scheme.

Model experiments on the microbial removal of chromium from contaminated groundwater.

A bacterial consortium with representatives of sulfate-reducing and denitrifying bacteria was selectively enriched. Model experiments under microaerobic conditions showed that it precipitated chromium from Cr (VI)-containing waters (area of a former electroplating factory, Leipzig, Germany) by two different mechanisms: by sulfate reduction and precipitation as sulfide, and by some direct reduction. Sulfate reduction needed fatty acids as organic substrates and resulted at the first stage in no sulfide accumulation. In the absence of the fatty acids but with straw as organic substrate, the direct reduction of chromium was observed without sulfate reduction. In this case Cr (VI)-reduction rate correlated with that of the denitrification.

Accelerated fractionation of heavy metals in contaminated soils and sediments using rotating coiled columns.

A new approach to performing an accelerated sequential extraction of trace elements from solid samples has been proposed. It has been shown that rotating coiled columns (RCC) earlier used in counter-current chromatography can be successfully applied to the dynamic leaching of heavy metals from soils and sediments. A solid sample was retained in the rotating column as the stationary phase under the action of centrifugal forces while different eluents (aqueous solutions of complexing reagents, mineral salts and acids) were continuously pumped through. The procedure developed is time saving and requires only 4-5 h instead of the several days needed for traditional sequential extraction (TSE), complete automation being possible. Losses of solid sample are minimal. In most cases the recoveries of readily bioavailable and leachable forms of Pb, Zn, and Cd are higher, if a dynamic extraction in RCC is used. Since naturally occurring processes are always dynamic, continuous extraction in RCC may help to estimate the contents of leachable forms and their potential risk for the environment more correctly than batch TSE. The Kersten-Foerstner and McLaren-Crawford leaching schemes have been compared, the former has been found to be preferable.

Application of natural zeolites for preconcentration of arsenic species in water samples.

Zeolites of the clinoptilolite type produced in Mexico and Hungary were investigated with respect to their sorption efficiency for various redox species of arsenic. Long-term experiments showed that arsenate remains stable for a long period in spiked deionised water and drinking water, as well as in the surface water of the Biela valley in Saxony, Germany. Both clinoptilolites are able to decrease the initial arsenic concentration of 200 microg l(-1) by more than 75% in deionised, drinking, ground and surface waters. In the case of the Mexican zeolite, both the arsenite and the arsenate concentrations (200 microg l(-1)) can be lowered from 200 microg l(-1) to 10 microg l(-1), which is the World Health Organisation's (WHO's) recommended maximum level. It was found that the presence of cations and anions in the natural waters of Biela, Germany, and Zimapán, Mexico, did not reduce the efficiency of the selected zeolites. The Hungarian zeolite removed 75% of the arsenate in the Zimapán water and only 50% when the sample was first acidified. This zeolite totally desorbed the fixed arsenic into a water volume that was half the volume in the adsorption experiment.

Evaluation of extraction procedures for the ion chromatographic determination of arsenic species in plant materials.

The determination of arsenic species in plants grown on contaminated sediments and soils is important in order to understand the uptake, transfer and accumulation processes of arsenic. For the separation and detection of arsenic species, hyphenated techniques can be applied successfully in many cases. A lack of investigations exists in the handling (e.g., sampling, pre-treatment and extraction) of redox- and chemically labile arsenic species prior to analysis. This paper presents an application of pressurized liquid extraction (PLE) using water as the solvent for the effective extraction of arsenic species from freshly harvested plants. The method was optimized with respect to extraction time, number of extraction steps and temperature. The thermal stability of the inorganic and organic arsenic species under PLE conditions (60-180 degrees C) was tested. The adaptation of the proposed extraction method to freeze-dried, fine-grained material was limited because of the insufficient reproducibility in some cases.

Separation of unmodified polystyrene nanosphere standards by capillary zone electrophoresis.

Size separation of five unmodified polystyrene nanosphere standards with diameters between 50 and 600 nm has been achieved in phosphate buffer solutions as carrier electrolyte. The electrophoretic mobility increases with particle diameter. Optical spectra was shown to be different for particles of different size. Effects of injection time, applied voltage, pH, and phosphate concentration in carrier electrolyte on particle separation were studied. Under optimal conditions the peak efficiency ranged from 600 to 10,500 theoretical plate numbers depending on nanosphere diameter was achieved.

Kinetics of the arsenite oxidation in seepage water from a tin mill tailings pond.

The kinetic of the oxidation of trivalent arsenic was investigated in synthetic as well as in natural samples of a tin mill seepage water. The influence of ferric ions and solid MnO(2) on the process was studied. To determine the time dependence of the concentrations of the arsenic species, a series of samples were taken sequentially and analysed by coupling of ionchromatographic separation and ICP-MS detection. To investigate the naturally occurring oxidation reaction, original seepage water samples were filtered and spiked with As(III) (1 mg l(-1)) and Fe(II) (10 mg l(-1)) and shaken providing intensive contact with the air. Additional synthetic samples buffered with carbonate were used in similar experiments to simplify the system. The reaction was incomplete in the presence of excess of iron for both types of samples. The oxidation of As(III) was complete within 8 h in the presence of MnO(2) (10 mg), but there was a difference in oxidation rates between the natural and the synthetic samples. The results are discussed with respect to the redox potentials and equilibrium constants.

Determination of arsenic species in water, soils and plants.

Ion chromatographic separation coupled with ICP-MS was used to determine arsenic species in plant and soil extracts. A scheme for growth, harvesting, sample pre-treatment and analysis was developed for the arsenic species to enable determination. Preliminary results obtained with ten herb plants grown on arsenic-contaminated soil compared to non-contaminated soil show a heterogeneous pattern of accumulation rate, metabolization and detoxification mechanisms in monocots and dicots. Arsenite appears to be the major component in plants with good growth. Organic arsenic species were even detected at very low concentrations (< 150 microg kg(-1) (dry mass)).

Determination of flotation reagents used in tin-mining by capillary electrophoresis.

Alkyl xanthates (O-alkyl dithiocarbonates) and phosphonates are important organic collectors for the flotation of metals from crude ore. Leaching from waste dumps into river and ground water, these substances can cause environmental pollution. A capillary electrophoretic method for the routine determination of ethyl, isopropyl, hexyl xanthate, and styrene phosphonate has been developed. Separation within 12 min could be achieved in borate pH 8.8 performing UV detection at 254 and 300 nm simultaneously. To improve the limits of detection obtained with hydrodynamic injection (0.4-1.5 ppm), field amplified sample injection (FASI) and stacking were investigated. An increase in sensitivity up to 4-8 fold could be achieved by pressure assisted FASI. Applying a stacking method to enrich the analytes by filling the capillary with sample solution to one third of its length, the limits of detection could be decreased to 10-40 ppb. Water samples from a former tin ore mining area have been analyzed using the optimized stacking technique. Quantitation was performed by standard addition. Good precision and accuracy were obtained, making this robust capillary electrophoretic method well-suited for routine analysis.

Quantitative determination of sulfur-containing anions in complex matrices with capillary electrophoresis and conductivity detection.

The analysis of sulfur species in complex matrices, like environmentally related samples, requires selective and sensitive as well as robust determination methods. As many as possible different anions need to be quantified in a reasonable analysis time. Besides ion chromatography, capillary electrophoresis has proven to be a very efficient technique for the separation and determination of ionic compounds. With the advantages of less sample and solvent consumption compared to conventional LC, short separation time, inexpensive and robust capillaries, CE was used to separate the anions sulfate, sulfite, thiosulfate, thiocyanate and sulfide. Detection and injection modes and the composition of the separation buffers have been varied to find the most suitable conditions. Conductivity detection after electrokinetic sample injection and improvement of calibration linearity allowed the determination of sulfur containing anions with low limits of detection (8 to 50 micrograms/l). The developed CE method was applied to the analysis of water from an open-pit mining lake.

Stability and determination of aflatoxins by high-performance liquid chromatography with amperometric detection.

A method based on reversed-phase high-performance liquid chromatography (RP-HPLC) with amperometric detection with a glassy carbon electrode at a constant potential of 1.4 V is reported for the separation and identification of aflatoxins B1, B2, G1 and G2 in a model mixture. The chromatography was performed on a PAH-Baker column with a ternary mobile phase containing methanol, acetonitrile and aqueous LiClO4 electrolyte. Aflatoxin G1 showed the highest electroactivity in the compound series studied. Calibration curves of aflatoxins G1 and B2 were linear up to 0.2 and 0.3 mmol/l, respectively. Sensitivity varied between 7 and 10 ng for the different aflatoxins. The combination of different HPLC detectors in the analysis of these compounds was applied to investigate the stability of aflatoxins G1 and B2.

Determination of Anionic, Neutral, and Cationic Species of Arsenic by Ion Chromatography with ICPMS Detection in Environmental Samples.

Ion chromatographic methods developed to separate either cationic, neutral, and anionic arsenic species or soluble and suspended arsenic species were successfully used in DORM-2 standard reference material and in water samples of environmental interest. The most effective separation of the analytes within 10 min was achieved with a nitric acid gradient elution using a strong anion-exchange stationary phase with additional capacity for hydrophobic interactions (IonPac AS7). The elemental-specific detection mode allows the sensitive determination of the arsenic species in the submicrogram per liter range. The calibration results were compared with those obtained by an alkaline water-methanol mixed eluent combined with a weak anion-exchange column (IonPac AS4A-SC). Differences in sensitivities were eclipsed by the low level of the baseline and the noise when using nitric acid. The gradient method was used to determine arsenic species in highly ferrous/ferric-contaminated leachates of lignite spoil. The companion elements underwent parallel screening to explain the interactions of arsenic species with the major elements.

Sensitive determination of arsenite by capillary zone electrophoresis with direct photometric detection.

The effect of the sample matrix type (water and aqueous solutions containing phosphate buffer, 3-[cyclohexylamino]-1-propanesulfonic acid [CAPS], and sodium chloride solutions) on the migration behavior and peak parameters of As(III), As(V), and dimethylarsinate was studied. CAPS is found to be the most effective additive for As(III) peak amplification. The reasons for additive influence are discussed. The pH of the carrier electrolyte has been optimized with respect to As(III) peak height and shift of the peak position in electropherograms from the position of the sample matrix plug. Under optimal conditions, a peak efficiency expressed as the number of theoretical plates per meter (N) of 50,460 and a detection limit of 0.05 mg L-1 for As(III) were achieved.

Elimination of sulfate interferences in the chromatographic determination of o-phosphate using liquid-liquid extraction.

A liquid-liquid extraction procedure for the elimination of high levels of sulfate is described. The proposed method allows the ion-chromatographic determination of ppb concentrations of phosphate in the presence of a 20 000-fold excess of sulfate. The liquid anion exchange resin Amberlite LA-2 was selected to retain sulfate from the sample solution acidified by acetic acid as well as cation-exchange cartridges in the H-form. The detection limit for phosphate was 0.03 mg/L.

Speciation analysis of arsenic and selenium compounds by capillary electrophoresis.

High-performance capillary electrophoresis is applied to the separation of different inorganic and organic arsenic and selenium compounds. In comparison with UV-detection, an approach with conductivity detection is described expecting higher sensitivity and universality. In this case the capillary was statically modified with CTAB before the electromigration procedure. The separation was performed with an electrolyte system consisting of CHES and Triton X-100. Detection limits of 0.06 mg/L or lower were obtained for As(V) and Se(VI). Water samples of an arsenic-polluted tailing of tin mining processes were analysed for anions as well as arsenic and selenium species.