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.     

Can Humans Metabolize Arsenic Compounds to Arsenobetaine?

Arsenic compounds were determined in 21 urine samples collected from a male volunteer. The volunteer was exposed to arsenic through either consumption of codfish or inhalation of small amounts of (CH₃)₃As present in the laboratory air. The arsenic compounds in the urine were separated and quantified with an HPLC–ICP–MS system equipped with a hydraulic high-pressure nebulizer. This method has a determination limit of 0.5 μg As dm⁻³ urine. To eliminate the influence of the density of the urine, creatinine was determined and all concentrations of arsenic compounds were expressed in μg As g⁻¹ creatinine. The concentrations of arsenite, arsenate and methylarsonic acid in the urine were not influenced by the consumption of seafood. Exposure to trimethylarsine doubled the concentration of arsenate and increased the concentration of methylarsonic acid drastically (0.5 to 5 μg As g⁻¹ creatinine). The concentration of dimethylarsinic acid was elevated after the first consumption of fish (2.8 to 4.3 μg As g⁻¹ creatinine), after the second consumption of fish (4.9 to 26.5 μg As g⁻¹ creatinine) and after exposure to trimethyl- arsine (2.9 to 9.6 μg As g⁻¹ creatinine). As expected, the concentration of arsenobetaine in the urine increased 30- to 50-fold after the first consumption of codfish. Surprisingly, the concentration of arsenobetaine also increased after exposure to trimethylarsine, from a background of approximately 1 μg As g⁻¹ creatinine up to 33.1 μg As g⁻¹ creatinine. Arsenobetaine was detected in all the urine samples investigated. The arsenobetaine in the urine not ascribable to consumed seafood could come from food items of terrestrial origin that—unknown to us—contain arsenobetaine. The possibility that the human body is capable of metabolizing trimethyl- arsine to arsenobetaine must be considered. © 1997 by John Wiley & Sons, Ltd.     

Arsenic compounds in terrestrial organisms. IV. Green plants and lichens from an old arsenic smelter site in Austria

Two lichens and 12 green plants growing at a former arsenic roasting facility in Austria were analyzed for total arsenic by ICP–MS, and for 12 arsenic compounds (arsenous acid, arsenic acid, dimethylarsinic acid, methylarsonic acid, arsenobetaine, arsenocholine, trimethylarsine oxide, the tetramethylarsonium cation and four arsenoriboses) by HPLC–ICP–MS. Total arsenic concentrations were in the range of 0.27 mg As (kg dry mass)⁻¹ (Vaccinium vitis idaea) to 8.45 mg As (kg dry mass)⁻¹ (Equisetum pratense). Arsenic compounds were extracted with two different extractants [water or methanol/water (9:1)]. Extraction yields achieved with water [7% (Alectoria ochroleuca) to 71% (Equisetum pratense)] were higher than those with methanol/water (9:1) [4% (Alectoria ochroleuca) to 22% (Deschampsia cespitosa)]. The differences were caused mainly by better extraction of inorganic arsenic (green plants) and an arsenoribose (lichens) by water. Inorganic arsenic was detected in all extracts. Dimethylarsinic acid was identified in nine green plants. One of the lichens (Alectoria ochroleuca) contained traces of methylarsonic acid, and this compound was also detected in nine of the green plants. Arsenobetaine was a major arsenic compound in extracts of the lichens, but except for traces in the grass Deschampsia cespitosa, it was not detected in the green plants. In contrast to arsenobetaine, trimethylarsine oxide was found in all samples. The tetramethylarsonium cation was identified in the lichen Alectoria ochroleuca and in four green plants. With the exception of the needles of the tree Larix decidua the arsenoribose (2′R)‐dimethyl[1‐O‐(2′,3′‐dihydroxypropyl)‐5‐deoxy‐β‐D ‐ribofuranos‐5‐yl]arsine oxide was identified at the low μg kg⁻¹ level or as a trace in all plants investigated. In the lichens an unknown arsenic compound, which did not match any of the standard compounds available, was also detected. Arsenocholine and three of the arsenoriboses were not detected in the samples. Copyright © 2000 John Wiley & Sons, Ltd.     

Organoarsenic compounds in plants and soil on top of an ore vein

Plants and soil collected above an ore vein in Gasen (Austria) were investigated for total arsenic concentrations by inductively coupled plasma mass spectrometry (ICP‐MS). Total arsenic concentrations in all samples were higher than those usually found at non‐contaminated sites. The arsenic concentration in the soil ranged from ∼700 to ∼4000 mg kg⁻¹ dry mass. Arsenic concentrations in plant samples ranged from ∼0.5 to 6 mg kg⁻¹ dry mass and varied with plant species and plant part. Examination of plant and soil extracts by high‐performance liquid chromatography–ICP‐MS revealed that only small amounts of arsenic (<1%) could be extracted from the soil and the main part of the extractable arsenic from soil was inorganic arsenic, dominated by arsenate. Trimethylarsine oxide and arsenobetaine were also detected as minor compounds in soil. The extracts of the plants (Trifolium pratense, Dactylis glomerata, and Plantago lanceolata) contained arsenate, arsenite, methylarsonic acid, dimethylarsinic acid, trimethylarsine oxide, the tetramethylarsonium ion, arsenobetaine, and arsenocholine (2.5–12% extraction efficiency). The arsenic compounds and their concentrations differed with plant species. The extracts of D. glomerata and P. lanceolata contained mainly inorganic arsenic compounds typical of most other plants. T. pratense, on the other hand, contained mainly organic arsenicals and the major compound was methylarsonic acid. Copyright © 2002 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.     

Arsenobetaine and other arsenic species in mushrooms

Arsenic species in arsenic accumulating mush- rooms (Sarcosphaera coronaria, Laccaria amethystina, Sarcodon imbricatum, Entoloma lividum, Agaricus haemorrhoidaius, Agaricus placomyces, Lycoperdon perlatum) were determined. HPLC/ICP MS and ion-exchange chromatogra- phy–instrumental neutron activation analysis (NAA) combinations were used. The remarkable accumulator Sarcosphaera coronaria (up to 2000 mg As kg^?1 dry wt) contained only methylarsonic acid, Entoloma lividum only arsenite and arsenate. In Laccaria amethystina dimethylarsinic acid was the major arsenic compound. Sarcodon imbricatum and the two Agaricus sp. were found to contain arsenobetaine as the major arsenic species, a form which had previously been found only in marine biota. Its identification was confirmed by electron impact MS.     

Determination of inorganic arsenic and organic arsenic compounds in marine organisms by hydride generation/cold trap/gas chromatography— mass spectrometry

The behavior of arsenite, methylarsonic acid, dimethylarsinic acid, trimethylarsine oxide, dimethyl-R-arsine oxides, and trimethyl-R-arsonium compounds (R = carboxymethyl, 2-carboxyethyl, 2-hydroxyethyl) toward sodium borohydride and hot aqueous sodium hydroxide was investigated. The arsines obtained by sodium borohydride reduction of the undigested and digested solutions were collected in a liquid-nitrogen cooled trap, separated with a gas chromatograph, and detected with a mass spectrometer in the selected-ion-monitoring mode. The investigated arsenic compounds were stable in hot 2 mol dm^?3 sodium hydroxide except arsenobetaine [trimethyl(carboxymethyl)arsonium zwitterion] that was converted to trimethylarsine oxide, and dimethyl(ribosyl)arsine oxides that were decomposed to dimethylarsinic acid. Hydride generation before and after digestion of extracts from marine organisms allowed inorganic arsenic, methylated arsenic, arsenobetaine, and ribosyl arsenic compounds to be identified and quantified. This method was applied to extracts from shellfish, fish, crustaceans, and seaweeds.     

Arsenic Compounds in Terrestrial Organisms I: Collybia maculata,Collybia butyracea and Amanita muscaria from Arsenic Smelter Sites in Austria

Three mushroom species from two old arsenic smelter sites in Austria were analyzed for arsenic compounds. The total arsenic concentrations were determined by ICP–MS. Collybia maculata contained 30.0 mg, Collybia butyracea 10.9 mg and Amanita muscaria 21.9 mg As kg⁻¹ dry mass. The arsenic compounds extracted with methanol/water (9:1) from the dried mushroom powders were separated by HPLC on anion-exchange and reversed-phase columns and detected by ICP-MS using a hydraulic high-pressure nebulizer. In Collybia maculata almost all arsenic is present as arsenobetaine. Collybia butyracea contained mainly arsenobetaine (8.8 mg As kg⁻¹ dry mass) and dimethylarsinic acid (1.9 mg As kg⁻¹). Amanita muscaria contained arsenobetaine (15.1 mg As kg⁻¹), traces of arsenite, dimethylarsinic acid and arsenate, and surprisingly arsenocholine (2.6 mg As kg⁻¹) and a tetramethylarsonium salt (0.8 mg As kg⁻¹). © 1997 by John Wiley & Sons, Ltd.     

Tissue accumulation and distribution of arsenic compounds in three marine fish species: relationship to trophic position

In this study the accumulation and distribution of arsenic compounds in marine fish species in relation to their trophic position was investigated. Arsenic compounds were measured in eight tissues of mullet Mugil cephalus (detritivore), luderick Girella tricuspidata (herbivore) and tailor Pomatomus saltatrix (carnivore) by high performance liquid chromatography–inductively coupled plasma‐mass spectrometry. The majority of arsenic in tailor tissues, the pelagic carnivore, was present as arsenobetaine (86–94%). Mullet and luderick also contained high amounts of arsenobetaine in all tissues (62–98% and 59–100% respectively) except the intestines (20% and 24% respectively). Appreciable amounts of dimethylarsinic acid (1–39%), arsenate (2–38%), arsenite (1–9%) and trimethylarsine oxide (2–8%) were identified in mullet and luderick tissues. Small amounts of arsenocholine (1–3%), methylarsonic acid (1–3%) and tetramethylarsonium ion (1–2%) were found in some tissues of all three species. A phosphate arsenoriboside was identified in mullet intestine (4%) and from all tissues of luderick (1–6%) except muscle. Pelagic carnivore fish species are exposed mainly to arsenobetaine through their diet and accumulate the majority of arsenic in tissues as this compound. Detritivore and herbivore fish species also accumulate arsenobetaine from their diet, with quantities of other inorganic and organic arsenic compounds. These compounds may result from ingestion of food and sediment, degradation products (e.g. arsenobetaine to trimethylarsine oxide; arsenoribosides to dimethylarsinic acid), conversion (e.g. arsenate to dimethylarsinic acid and trimethylarsine oxide by bacterial action in digestive tissues) and/or in situ enzymatic activity in liver tissue. Copyright © 2001 John Wiley & Sons, Ltd.     

Arsenic Compounds in Terrestrial Organisms II: Arsenocholine in the Mushroom Amanita muscaria

Arsenic compounds were identified and quantified in the mushroom Amanita muscaria, collected close to a facility that had roasted arsenic ores. The powdered dried mushrooms were extracted with methanol/water (9:1), the extracts were concentrated and the concentrates were dissolved in water. The resulting solutions were chromatographed on anion-exchange, cation-exchange and reversed- phase columns. Arsenic was detected on-line with an ICP–MS detector equipped with a hydraulic high-pressure nebulizer. Arsenite, arsenate, dimethylarsinic acid and the tetramethylarsonium cation were minor arsenic compounds (∼2% each of the total 22 mg kg⁻¹ dry mass), and arsenobetaine, arsenocholine (∼15% each) and several unidentified arsenic compounds (∼60%) were the major arsenic compounds in Amanita muscaria. The presence of arsenocholine (detected for the first time in a terrestrial sample) was ascertained by matching retention times in the anion-exchange, cation- exchange and reversed-phase chromatograms with the retention time of synthetic arsenocholine bromide and chromatographing extracts spiked with arsenocholine bromide. © 1997 John Wiley & Sons, Ltd.     

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.     

Distribution and fate of biologically formed organoarsenicals in coastal marine sediment

Marine organisms, including phyto‐ and zoo‐plankton, macroalgae, and animals, concentrate arsenic in various organic forms. However, the distribution and fate of these organoarsenicals in marine environments remains unclear. In this study, the distribution of organoarsenicals in coastal marine sediment in Otsuchi Bay, Japan, has been determined. Methylarsonic acid, dimethylarsinic acid, trimethylarsine oxide, arsenobetaine, arsenocholine and other unidentified arsenic species were detected in marine sediment by high‐performance liquid chromatography–inductively coupled plasma mass spectrometry analysis of methanol–water extracts. Arsenobetaine was the dominant organoarsenical at four of the seven stations where tests were carried out, and unidentified species or dimethylarsinic acid dominated at the other stations. Total organoarsenicals (as arsenic) in the surface sediment amounted to 10.6–47.5 µg kg^?1 dry sediment. Core analysis revealed that concentrations of organoarsenicals decreased with depth, and they are considered to be degraded within 60 years of deposition. These results show that organoarsenicals formed by marine organisms are delivered to the sediment and can be degraded within several decades. Copyright © 2005 John Wiley & Sons, Ltd.     

Ubiquity of arsenobetaine in marine animals and degradation of arsenobetaine by sedimentary micro-organisms

Arsenic compounds were extracted with chloroform/methanol/water from tissues of marine animals (four carnivores, five herbivores, five plankton feeders). The extracts were purified by cation and anion exchange chromatography. Arsenobetaine [(CH₃)₃As⁺CH₂COO^?], dimethylarsinic acid [(CH₃)₂AsOOH], trimethylarsine oxide [(CH₃)₃AsO] and arsenite, arsenate, and methylarsonic acid [(CH₃)AsO(OH)₂] as a group with the same retention time were identified by high-pressure liquid chromatography. Arsenic was determined in the collected fractions by graphite furnace atomic absorption spectrometry. Arsenobetaine found in all the animals was almost always the most abundant arsenic compound in the extracts. These results show that arsenobetaine is present in marine animals independently of their feeding habits and trophic levels. Arsenobetaine-containing growth media (ZoBell 2216E; solution of inorganic salts) were mixed with coastal marine sediments as the source of microorganisms. Arsenobetaine was converted in both media to trimethylarsine oxide and trimethylarsine oxide was converted to arsenite, arsenate or methylarsonic acid but not to dimethylarsinic acid. The conversion rates in the inorganic medium were faster than in the ZoBell medium. Two dominant bacterial strains isolated from the inorganic medium and identified as members of the Vibro–Aeromonas group were incapable of degrading arsenobetaine.     

Cytotoxicological aspects of organic arsenic compounds contained in marine products using the mammalian cell culture technique

Arsenobetaine, arsenocholine, trimethylarsine oxide and tetramethylarsonium iodide, which are contained in marine fishery products, were examined for their potencies on cell growth inhibition, chromosomal aberration and sister chromatid exchange (SCE). Arseno- betaine, the major water-soluble organic arsenic compound in marine animals, exhibited very low cytotoxicity towards mammalian cells. This compound showed no cell growth inhibition at a concentration of 10 mg cm⁻³ and the cytotoxicity was lower than 1/14 000th of that of sodium arsenite and 1/1600th of that of sodium arsenate towards BALB/c 3T3 cells. The chromosomal aberrations caused by arsenobetaine at a concentration of 10 mg cm⁻³ consisted mainly of chromatid gaps and chromatid breaks, but in this concentration chromosomal breakage owing to its osmotic pressure is likely to be considerable. No SCE was observed at a concentration of 1 mg cm⁻³. Arsenocholine and trimethylarsine oxide also showed no cell growth inhibited at a concentration of 10 mg cm⁻³. However, tetramethylarsonium iodide inhibition the growth of BALB/c 3T3 at a concentration of 8 mg cm⁻³. These compounds exhibited a low ability to induce chromosomal aberrations at a concentration range of 2–10 mg cm⁻³ and no SCE was observed at a concentration of 1.0 mg cm⁻³. These results suggested that the major and minor organic arsenic compounds contained in marine fishery products are much less cytotoxic inorganic arsenic, methylarsonic acid and dimethylarsinic acid. © 1998 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.     

Speciation of Arsenic Compounds in the Urine of Rats Orally Exposed to Dimethylarsinic Acid Ion Chromatography with ICP–MS as an Element-Selective Detector

A combined ion chromatography (IC) with inductively coupled plasma mass spectrometry (ICP—MS) system as an element-selective detector has been used for the determination of arsenic compounds. Seven arsenic compounds were separated by cation-exchange chromatography. Subsequently, the separated arsenic compounds were directly introduced into the ICP—MS and were detected at m/z =75. Detection limits for the seven arsenic compounds ranged from 0.8 to 3.8 μg As/l. The IC–ICP–MS system was applied to the determination of arsenic compounds in the urine of dimethylarsinic acid (DMAA)-exposed rats. DMAA was the most abundant arsenic compound detected. Arsenous acid, monomethylarsonic acid and trimethylarsine oxide were also detected.     

Conversion of arsenobetaine to dimethylarsinic acid by arsenobetaine-decomposing bacteria isolated from coastal sediment

Arsenobetain [(CH₃)₃As⁺CH₂COO^-]-containing growth media (1/5 ZoBell 2216E and solution of inorganic salts) were inoculated with two bacterial strains, which were isolated from a coastal sediment and identified as members of the Vibro-Aeromonas group, and incubated under aerobic and anaerobic conditions. Arsenobetaine was converted to a metabolite only under aerobic conditions. This arsenic metabolite was identified as dimethylarsinic acid [(CH₃)₂AsOOH] by hydride generation/cold trap/GC MS/SIM analysis and high-performance liquid-chromatographic behaviour. The conversion pattern shown by these arsenobetaine-decomposing bacteria (that is, arsenobetaine → dimethylarsinic acid) was fairly different from that shown by the addition of sediment itself as the source of arsenobetaine-decomposing micro-organisms (that is, arsenobetaine → trimethylarsine oxide → inorganic arsenic). This result suggests to us that various micro-organisms, including the arsenobetaine-decomposing bacteria isolated in this study, participate in the degradation of arsenobetaine in marine environments.     

Methylation and Demethylation of Dimethylarsinic Acid in Rats Following Chronic Oral Exposure

Metabolites of dimethylarsinic acid (DMA) were studied in rats chronically exposed to DMA in drinking water. The urine was collected by forced urination at the end of 8, 20 and 30 weeks and the feces at the end of 30 weeks. The samples were analyzed for arsenic species by a combined system of ion chromatography and inductively coupled plasma mass spectrometry (IC–ICP–MS). Increases in arsenite, DMA, trimethylarsine oxide and a still-to-be-identified arsenic compound (which was eluted immediately after monomethylarsonic acid on the chromatogram) were detected in both urine and feces. At the 100 mg l⁻¹ dose, DMA was the main component in the urine; arsenite was a main component in the feces. The results indicate that, besides undergoing methylation, DMA can be demethylated to inorganic arsenic, and demethylation of DMA may be associated with intestinal bacteria     

Determination of arsenic compounds in marine mammals with high-performance liquid chromatography and an inductively coupled plasma mass spectrometer as element-specific detector

Total arsenic concentrations and the concentrations of individual arsenic compounds were determined in liver samples of pinnipeds [nine ringed seals (Phoca hispida), one bearded seal (Erginathus barbatus)] and cetaceans [two pilot whales (Globicephalus melas), one beluga whale (Deliphinapterus leucus)]. Total arsenic concentrations ranged from 0.167 to 2.40 mg As kg⁻¹ wet mass. The arsenic compounds extracted from the liver samples with a methanol/water mixture (9:1, v/v) were identified and quantified by anion- and cation-exchange chromatography. An ICP–MS equipped with a hydraulic high-pressure nebulizer served as the arsenic-specific detector. Arsenobetaine (0.052–1.67 mg As kg⁻¹ wet mass) was the predominant arsenic compound in all the liver samples. Arsenocholine was present in all livers (0.005–0.044 mg As kg⁻¹ wet mass). The tetramethylarsonium cation was detected in all pinnipeds ( < 0.009 to 0.043 mg As kg⁻¹) but not in any of the cetaceans. The concentration of dimethylarsinic acid ranged from < 0.001 to 0.109 mg As kg⁻¹ wet mass. Most of the concentrations for methylarsonic acid ( < 0.001 to 0.025 mg As kg⁻¹ wet mass) were below the detection limit. Arsenous acid and arsenic acid concentrations were below the detection limit of the method (0.001 mg As kg⁻¹). An unknown arsenic compound was present in all liver samples at concentrations from 0.002–0.027 mg As kg⁻¹. © 1998 John Wiley & Sons, Ltd.     

The fate of organoarsenic compounds in marine ecosystems

Microbial degradation experiments were performed with each standard arsenical [arsenobetaine, trimethylarsine oxide, dimethylarsinic acid, methanearsonic acid, inorganic arsenic(V) and inorganic arsenic(III)]. As typical origins for marine micro-organisms, sediments, macro-algae, mollusc intestine and suspended substances were used. The results were from these experiments led us to the following conclusions: (1) there is an arsenic cycle which begins with the methylation of inorganic arsenic on the route to arsenobetaine and terminates with the complete degradation of arsenobetaine to inorganic arsenic; (2) all the organoarsenic compounds which are derived from inorganic arsenic in seawater, through the food chains, have the fate that they, at least in part, finally return to the original inorganic arsenic.