Adsorption of Inorganic and Organic Arsenic Compounds by Aluminium-loaded Coral Limestone

Coral limestones were treated with an aqueous solution of aluminium sulfate and thereby aluminium-loaded coral limestones (Al-CL) were prepared. By use of Al-CL as an adsorbent, the adsorption of inorganic arsenic compounds (arsenate [As(V)] and arsenite [As(III)] and of organic arsenic compounds (methylarsonic acid, dimethylarsinic acid, and arsenobetaine) was examined. The adsorption ability of Al-CL is superior to that of iron(III)-loaded coral limestone (Fe-CL) for As(V), As(III), methylarsonic acid and dimethylarsinic acid. The adsorption of As(V) and As(III) is almost independent of the initial pH over a wide range (2 or 3 to 11). The addition of other anions, such as chloride, nitrate, sulfate and acetate, in the solution does not affect the adsorption of As(V) and As(III), whereas the addition of phosphate greatly interferes with the adsorption. Arsenic adsorption is effectively applied to a column-type operation and the adsorption capability for As(V) is 150 μg/g coral limestone.     

Arsenic Compounds in Higher Fungi

In 50 mushroom species (56 samples) from Slovenia, Switzerland, Brazil, Sweden, The Netherlands and USA, total arsenic was determined by radiochemical neutron activation analysis (RNAA). Arsenic concentrations ranged from 0.1 to 30 μg g⁻¹ (dry mass). Arsenic compounds were determined in methanol extracts from the mushrooms by HPLC–ICP–MS. The aim of the study was not only to quantify arsenic compounds in mushrooms but also to uncover trends relating the methylating ability of a mushroom to its taxonomic or evolutionary status. The main arsenic compound found in many mushrooms (various puffballs, Agaricales and Aphyllophorales) was arsenobetaine. Arsenate [As(V)] was the main arsenic species in Laccaria fraterna and Entoloma rhodopolium and arsenite [As(III)] in Tricholoma sulphureum. A mixture of arsenite and arsenate was present in Amanita caesarea. Dimethylarsinic acid (DMA) and methylarsonic acid were present in many mushrooms, but generally as minor components. In Laccaria laccata, Leucocoprinus badhamii and Volvariella volvacea, DMA was the major metabolite. Arsenocholine (AC) and the tetramethylarsonium ion were present in a few species, generally at low concentrations, except for Sparassis crispa, in which AC was the main compound. Tri- methylarsine oxide was not found in any of the mushrooms. In some species small amounts of unknown compounds were also present. The possible taxonomic significance of the metabolite patterns and the predominance of arsenobetaine in more advanced fungal types are discussed. © 1997 John Wiley & Sons, Ltd.     

Identification of extracellular arsenical metabolites in the growth medium of the microorganisms apiotrichum humicola and scopulariopsis brevicaulis

The separation and identification of some of the arsenic species produced in cells present in the growth medium when the microorganisms Apiotrichum humicola (previously known as Candida humicola) and Scopulariopsis brevicaulis were grown in the presence of arsenicals were achieved by using hydride generation–gas chromatography–atomic absorption spectrometry methodology (HG GC AA). Arsenite, monomethylarsonate, dimethylarsinate and trimethylarsine oxide were detected following incubation with arsenate. With arsenite as a substrate, the metabolites were monomethylarsonate, dimethylarsinate and trimethylarsine oxide; monomethylarsonate afforded dimethylarsinate and trimethylarsine oxide, and dimethylarsinate afforded trimethylarsine oxide. Trimethylarsine was not detected when the arsenic concentration was 1 ppm.     

The Cumulation of Chromium and Arsenic Species in Fish (Poecilia reticulata)

Abstract

Chromium-51 and arsenic-74 were used for the investigation of the uptake and the release of different chromium and arsenic species in fish. It has been found that only trimethylarsine can be rapidly taken up directly from water. The release of chromium(III), consumed by fish in food, is very rapid: about 99.9% of chromium is released within a few days. The same results were obtained with chromium(III) acetylacetonate or chromium(III) ethylenediaminotetraacetate. About 95% of arsenic acid, methylarsonic acid, dimethylarsinic acid or arsenic(III) diethyldithiocarbamate are released within a few days whereas the remaining arsenic is released with the biological half time 35 ± 5 days.     

Induction of mitotic arrest and aneuploidy by organic arsenic compounds in human lymphocytes

Inorganic arsenic is methylated in the mammalian body to methylarsonic acid (MMA), dimethylarsinic acid (DMA) and trimethylarsine oxide (TMA). To achieve a more precise understanding of arsenic carcinogenicity, we examined the genotoxic effects of organic arsenic compounds on human lymphocytes by assessing induction of mitotic arrest, sister chromatid exchange (SCE) and aneuploidy. MMA, DMA and TMA arrested mitosis, DMA induced hyperdiploid cells, and DMA and TMA induced tetraploid cells. Of the three arsenic metabolites tested, DMA had the strongest effects on cell mitosis and aneuploidy induction. DMA arrested mitosis and induced c-mitosis significantly. These results suggest that DMA arrests mitosis and induces aneuploidy through spindle disruptions similar to those observed with known spindle poisons, such as colchicine or vinblastine. Since aneuploidy has been thought to be associated with tumor induction or neoplastic transformation, induction of aneuploidy by organic metabolites of arsenic may play a major role in arsenic carcinogenesis in humans. © 1997 John Wiley & Sons, Ltd.     

Metabolism of arsenic compounds by the blue mussel mytilus edulis after accumulation from seawater spiked with arsenic compounds

Blue mussels (Mytilus edulis) were exposed to 100 μg As dm^?3 in the form of arsenite, arsenate, methylarsonic acid, dimethylarsinic acid, arsenobetaine, arsenocholine, trimethylarsine oxide, tetramethylarsonium iodide or dimethyl-(2-hydroxyethyl)arsine oxide in seawater for 10 days. The seawater was renewed and spiked with the arsenic compounds daily. Analyses of water samples taken 24 h after spiking showed that arsenobetaine and arsenocholine had been converted to trimethylarsine oxide, whereas trimethylarsine oxide and tetramethylarsonium iodide were unchanged. Arsenobetaine was accumulated by mussels most efficienty, followed in efficiency by arsenocholine and tetramethylarsonium iodide. None of the other arsenic compounds was significantly accumulated by the mussels. Extraction of mussel tissues with methanol revealed that control mussels contained arsenobetaine, a dimethyl-(5-ribosyl)arsine oxide and an additional arsenic compound, possibly dimethylarsinic acid. Mussels exposed to arsenobetaine contained almost all their experimentally accumulated arsenic as arsenobetaine, and mussels exposed to tetramethylarsonium iodide contained it as the tetramethylarsonium compound. Mussels exposed to arsenocholine had arsenobetaine as the major arsenic compound and glycerylphosphorylarsenocholine as a minor arsenic compound in their tissues. The results show that arsenobetaine and arsenocholine are efficiently accumulated from seawater by blue mussels and that in both cases the accumulated arsenic is present in the tissues as arsenobetaine. Consequently arsenobetaine and/or arsenocholine present at very low concentrations in seawater may be responsible for the presence of arsenobetaine in M. edulis and probably also among other marine animals. The quantity of arsenobetaine accumulated by the mussels decreases with increasing concentrations of betaine. HPLC-ICP-MS was found to be very powerful for the investigation of the metabolism of arsenic compounds in biological systems.     

Comparison of mild extraction procedures for determination of arsenic compounds in different parts of pepper plants (Capsicum annum,L.)

Eight extraction agents (water, methanol–water mixtures in various ratios, methanol, a 20 mmol l^?1 ammonium phosphate buffer, and a methanol–phosphate buffer) were tested for the extraction of arsenic compounds from fruits, stems + leaves, and roots of pepper plants grown on soil containing 17.2 mg kg^?1 of total arsenic. The arsenic compounds in the extracts were determined using high‐performance liquid chromatography–hydride generation inductively coupled plasma mass spectrometry. Whereas pure water was the most effective extraction agent for fruits (87 ± 3.3% extraction yield) and roots (96 ± 0.6% extraction yield), the 20 mM ammonium phosphate buffer at pH 6 extracted about 50% of the arsenic from stems + leaves. Decreasing extractability of the arsenic compounds was observed with increasing methanol concentrations for all parts of the pepper plant. In pepper fruits, arsenic(III), arsenic(V), and dimethylarsinic acid (DMA) were present (25%, 37%, and 39% respectively of the extractable arsenic). Arsenic(V) was the major compound in stems + leaves and roots (63% and 53% respectively), followed by arsenic(III) representing 33% and 42% respectively, and small amounts (not exceeding 5%) of DMA and methylarsonic acid were also detected. Hence, for a quantitative extraction of arsenic compounds from different plant tissues the extractant has to be optimized individually. Copyright © 2005 John Wiley & Sons, Ltd.     

The separation of dimethylarsinic acid,methylarsonous acid,methylarsonic acid,arsenate and dimethylarsinous acid on the Hamilton PRP‐X100 anion‐exchange column

In order to separate the potential arsenite metabolites methylarsonous acid and dimethylarsinous acid from arsenite, arsenate, methylarsonic acid and dimethylarsinic acid, the pH‐dependent retention behaviour of all six arsenic compounds was studied on a Hamilton PRP‐X100 anion‐exchange column with 30 mM phosphate buffers (pH 5, 6, 7, 8 and 9) containing 20% (v/v) methanol as mobile phase and employing an inductively coupled plasma atomic emission spectrometer (ICP–AES) as the arsenic‐specific detector. Baseline separation of dimethylarsinic acid, methylarsonous acid, methylarsonic acid, arsenate and dimethylarsinous acid was achieved with a 30 mmol dm⁻³ phosphate buffer (pH 5)–methanol mixture (80:20, v/v) in 25 min. Arsenite is not baseline‐separated from dimethylarsinic acid under these conditions. Copyright © 1999 John Wiley & Sons, Ltd.     

The lon-chromatographic behavior of arsenite,arsenate, methylarsonic acid and dimethylarsinic acid on the hamilton PRP-X100 anion-exchange column

The HPLC separation of arsenite, arsenate, methylarsonic acid and dimethylarsinic acid has been studied in the past but not in a systematic manner. The dependence of the retention times of these arsenic compounds on the pH of the mobile phase, on the concentration and the chemical composition of buffer solutions (phosphate, acetate, potassium hydrogen phthalate) and on the presence of sodium sulfate or nickel sulfate in the mobile phase was investigated using a Hamilton PRP-X100 anion-exchange column. With a flame atomic absorption detector and arsenic concentrations of at least 10 mg dm^?3 all investigated mobile phases will separate the four arsenic compounds at appropriate pH values in the range 4–8. The shortest analysis time (?3 min) was achieved with a 0.006 mol dm^?3 potassium hydrogen phthalate mobile phase at pH 4, the longest (?10 min) with 0.006 mol dm^?3 sodium sulfate at pH 5.9 at a flow rate of 1.5 cm³ min^?1. With a graphite furnace atomic absorption detector at the required, much lower, flow rate of ?0.2 cm³ min^?1 acceptable separations were achievable only with the pH 6 phosphate buffer (0.03 mol dm^?3) and the nickel sulfate solution (0.005 mol dm^?3) as the mobile phase. To become detectable approximately 100 ng arsenic from each arsenic compound (100 μl injection) must be chromatographed with the phosphate buffer, and approximately 10 ng with the nickel sulfate solution.     

Behaviour of organoarsenic compounds in contact with natural zeolites

Batch experiments were conducted on aqueous solutions containing arsenite, arsenobetaine, methylarsonic acid or phenylarsonic acid in contact with natural zeolites to examine their interaction. The concentration of the arsenic species in the liquid phase at equilibrium before and after contact was measured by means of liquid chromatography coupled with inductively coupled plasma mass spectrometry detection. Clinoptilolites completely removed arsenobetaine from the solution and the resulting amounts of dimethylarsinic acid were detected. The methylarsonic acid maximum concentration diminution was reached at a mass—to volume V value of m/V = 0.2. Phenylarsonic acid solution decreased its concentration 75% after treatment with clinoptilolites. Untreated mordenites in contact with arsenite solutions led to the formation of arsenate, whereas acid‐washed mordenites practically removed arsenobetaine and were less effective for methylarsonic acid. To show the incompatibility of molecular dimensions with the zeolite windows, the molecular parameters of surface area, molecular volume, molecular length, and the width and depth of arsenite, arsenate and a series of ten organic arsenic compounds were calculated. Since sorption onto the external zeolite surface rather than a sieve process defined the interaction, an acid‐catalysed reaction mechanism is proposed to explain the transformation results. Copyright © 2001 John Wiley & Sons, Ltd.     

Conversion of arsenobetaine by intestinal bacteria of a mollusc Liolophura japonica chitons

The intestinal micro-organisms of Liolophura japonica chitons converted arsenobetaine [(CH₃)₃As⁺CH₂COO^?] to trimethylarsine oxide [(CH₃)₃AsO] and dimethylarsinic acid [(CH₃)₂AsOOH] in the arsenobetaine-containing 1/5 ZoBell 2216E medium under aerobic conditions, no conversion being observed in an inorganic salt medium. This conversion pattern of arsenobetaine → trimethylarsine oxide ← dimethylarsinic acid was comparable with that shown by the microorganisms associated with marine macroalgae. On the other hand, no conversion was observed in either medium under anaerobic conditions.     

Uptake and degradation of arsenobetaine by the microorganisms occurring in sediments

We have reported the degradation of arsenobetaine [(CH₃)₃As⁺CH₂COO^?] to inorganic arsenic by microorganisms from various marine origins such as sediments. However, there was no information as to the fate of the ingested arsenobetaine within the body of the microorganisms before excretion. In this study, arsenobetaine and sediments were added to two culture media (1/5 Zobell 2216E and a solution of inorganic salts) and aerobically incubated at 25°C in the dark. Despite the degradation and complete disappearance of arsenobetaine from the filtrates of the incubation mixtures, the major arsenic compound from the microorganisms harvested from the mixtures was identified by HPLC as arsenobetaine throughout the incubation period. The presence of arsenobetaine was further confirmed by TLC and fast atom bombardment mass spectrometry (FAB MS). A minor arsenical also present in the incubated microorganisms, dimethylarsinic acid, was detected.     

Formation of arsenobetaine from arsenocholine by micro-organisms occurring in sediments

As one of the experiments to pursue marine circulation of arsenic, we studied microbiological conversion of arsenocholine to arsenobetaine, because arsenocholine may be a precursor of arsenobetaine in these ecosystems. Two culture media, 1/5 ZoBell 2216E and an aqueous solution of inorganic salts, were used in this in vitro study. To each medium (25 cm³) were added synthetic arsenocholine (0.2%) and about 1 g of the sediment, and they were aerobically incubated at 25°C in the dark. These conversion experiments were performed in May and July 1990. In both seasons, two or three metabolites were derived in each mixture. These metabolites were purified using cation-exchange chromatography. Their structures were confirmed as arsenobetaine, trimethylarsine oxide and dimethylarsinic acid by high-performance liquid chromatography, thin-layer chromatography, FAB mass spectrometry and a combination of gas-chromatographic separation with hydride generation followed by a cold-trap technique and selected-ion monitoring mass spectrometric analysis. From this and other evidence it is concluded that, in the arsenic cycle in these marine ecosystems, as recently postulated by us, the pathway arsenocholine → arsenobetaine → trimethylarsine oxide → dimethylarsinic acid → methanearsonic acid → inorganic arsenic can be carried out by micro-organisms alone.     

Effects of Arsenic Compounds on Proliferation and Nitric Oxide Synthesis in C3H 10T 1/2 Murine Fibroblasts

Exposure to arsenic, either through chronic consumption of contaminated water or inhalation, is associated with increased risk of cancer, yet the mechanism by which arsenicals promote neoplastic change remains undefined. The carcinogenic process involves the formation of heritable genetic changes in the DNA of normal cells and this process may be enhanced by environmental agents that increase cellular proliferation, increase DNA damage and decrease the ability to repair damage or cause immunosuppression. We describe the inhibition of cellular proliferation of C3H 10T1/2 murine fibroblasts in the presence of 1.0 μM arsenate or arsenite; yet cacodylic acid had no significant effect on cell growth in culture at this concentration. Both arsenate and cacodylate, at micromolar concentrations, slightly stimulated cell growth and cell density when cells were treated with interferon-γ/lipopolysaccharide (IFN-γ/LPS). At 1 μM , arsenate and cacodylate also slightly increased IFN-γ/LPS-induced nitric oxide (NO) synthesis in this cell line, consistent with the increase in cell number observed, whereas 1 μM arsenite significantly increased NO production on a per-cell basis. In contrast, arsenite significantly inhibited NO synthesis at concentrations above 10 μM arsenite as, to a lesser extent, did arsenate and cacodylate. These results suggest that ingestion of arsenicals could alter cellular generation of NO and interfere with its associated physiological functions. © 1997 by John Wiley & Sons, Ltd.     

Degradation of a tetramethylarsonium salt by microorganisms occurring in sediments and suspended substances under both aerobic and anaerobic conditions

Microbial degradation of a tetramethylarsonium salt during incubation at 25°C was investigated under both aerobic and anaerobic conditions. Two media (1/5 ZoBell 2216E and inorganic salt medium), added with the sediments or suspended substances as the sources of the microorganisms, were used. Degradation of the tetramethylarsonium salt occurred only in the ZoBell medium: under anaerobic conditions, trimethylarsine oxide and dimethylarsinic acid were derived with the sediments, and dimethylarsinic acid with the suspended substances, the salt degrading more rapidly with the former than with the latter. Small amounts of two metabolites, trimethylarsine oxide and inorganic arsenic(V), was also derived in the aerobically incubated ZoBell medium added with the suspended substances. This result means that the tetramethylarsonium salt is degraded to inorganic arsenic, which is the starting material for arsenic circulation in marine ecosystems, via trimethylarsine oxide and dimethylarsinic acid.     

Arsenobetaine-decomposing Ability of Marine Microorganisms Occurring in Particles Collected at Depths of 1100 and 3500 Meters

The arsenobetaine-decomposing ability of microorganisms occurring in sinking particles, which play a main role in the vertical transport of organic substances produced in the photic zone, was investigated. The microorganisms in particles collected in the deep sea, 1100 and 3500 m in depth, clearly showed decomposing ability. With the particles from 1100 m, the degradation products were the same as those produced by microorganisms occurring in sources in the photic zone, i.e. trimethylarsine oxide (TMAO), dimethylarsinic acid (DMA) and inorganic arsenic(V). At 3500 m, the degradation activity was diminished, smalls amount of DMA and TMAO being produced. These results suggest that arsenobetaine contained in the animals starts to degrade immediately after the death of the animals and their transformation to particles. The degradation of arsenobetaine to inorganic arsenic in our tentative arsenic cycle in marine ecosystems (inorganic arsenic to inorganic arsenic via the biosynthesis of arsenobetaine) may apply to the deep sea as well as to the photic zone. © 1997 by John Wiley & Sons, Ltd.     

氢化物发生原子荧光法测定聚氯化铝中的砷含量

建立了氢化物发生原子荧光法测定聚氯化铝中砷含量的检测方法。将聚氯化铝样品用硫酸溶解,蒸至近干,用氢化物发生原子荧光法测定其中的砷含量。在最佳测定条件下,砷的质量浓度在0~10.0μg/L范围内与荧光强度呈良好的线性关系,相关系数r=0.999 3,砷的检出限为0.03μg/g,样品加标回收率为82.5%~90.0%,测定结果的相对标准偏差为1.5%~1.9%。该法具有快速、准确、灵敏度高等优点。     

Biotransformation of [3H]methylarsonic acid in a static seawater system containing Mytilus californianus

Mytius californianus exposed for 9 days to a seawater system containing [³H]methylarsonic acid, was found to contain [³H]methylarsonic acid along with [³H]arsenobetaine and two unknown ³H-labeled compounds in the tissue parts of the mussel. A linear increase with time in the specific activity present in the flesh of Mytilus californianus was also observed. The highest specific activity was found in the visceral mass and the gills of the mussel.     

氢化物发生原子荧光法测定水处理剂聚合氯化铝中砷的含量

探讨了以硫酸预处理样品,硫脲-抗坏血酸混合液将As(Ⅴ)预先还原至As(Ⅲ),氢化物发生原子荧光法测定聚合氯化铝中砷含量的方法。结果表明,回收率为92.31%~105.10%,相对标准偏差为2.37%~5.55%。     

Studies of the uptake and binding of trace metals in fungi. Part II. Arsenic compounds in Laccaria amethystina

Caps of the edible mushroom Laccaria amethystina collected during September and October at forested sites in the vicinity of the town of Domzale in Central Slovenia, Yugoslavia, were found by neutron activation analysis (NAA) and hydride generation to have total arsenic concentrations between 109 and 200 mg As kg^?1 (dry mass). The extraction of fresh, frozen or freeze-dried caps with cold Tris buffer at pH 7.6, or with boiling water, transferred 60–70% of the arsenic into the aqueous phase. Sephadex gel permeation chromatography indicated that the arsenic compounds in these extracts were not associated with proteins or other organic compounds of molecular mass larger than 4000 Dal. Cation-exchange chromatography coupled with NAA, hydride generation, and reverse-phase chromatography with arsenic-specific detection (HPLC ICP) showed that dimethylarsinic acid is the major arsenic compound in the extracts. Methylarsonic acid and arsenate account for no more than 10% each of the total arsenic.