Kurt J. Irgolic

Arsenobetaine and other arsenic compounds in the National Research Council of Canada Certified Reference Materials DORM 1 and DORM 2

A silica-based cation-exchange column was used to determine the arsenic compounds in the National Research Council of Canada (NRCC) CRMs DORM 1 and DORM 2 (Dogfish Muscle). With a 20 mM aqueous pyridine mobile phase at pH 3.0, the concentration of arsenobetaine was only 10.7 mg kg–1 As in the extract of DORM 1. When the same extract was chromatographed on an anion-exchange column, 15.9±0.3 mg kg–1 As (arsenobetaine) were found. The calibration for arsenobetaine was linear from 0.5 µg dm–1 As to 10 mg dm–3 As. When the extracts were diluted with water the cation-exchange results approached the anion-exchange results. The multi-element capabilities of ICP-MS allowed the simultaneous monitoring of arsenic and alkali metals. Sodium and potassium were found to co-elute with arsenobetaine. When aqueous solutions of arsenobetaine with 250 mg dm–3 Na were chromatographed, the signal obtained for arsenobetaine was only 60% of the signal without sodium in the solution. When the pH of the 20 mM aqueous pyridine mobile phase was lowered, the alkali metals were separated from arsenobetaine and the results obtained from cation-exchange chromatography were not significantly different from the anion-exchange results. Because DORM 1 is no longer available, the arsenic compounds in DORM 2 were determined. No significant difference was found for the concentration of arsenobetaine (15.6±0.7 mg kg–1 As for DORM 1; 16.0±0.7 mg kg–1 As for DORM 2). The concentrations of the minor arsenic compounds (dimethylarsinic acid, arsenocholine, the tetramethylarsonium cation and an unknown arsenic compound) in DORM 2 were only half the concentrations in DORM 1.

Selenium containing amino acids and proteins in marine algae

Abstract The unicellular marine algae, Dunaliella primolecta Butcher, Chlorella sp. and Porphyridium cruentum (S.F. Grey) were grown in artificial sea water containing a sublethal concentration of selenite, 10−2 g Se/1. Both free-and protein-bound seleno-amino acids were identified. The initial steps of selenium incorporation seem to involve the use of the sulfur enzymatic machinery resulting in the replacement of some of the sulfur by selenium in both free amino acids and proteins. At relatively low selenium concentrations, selenium-specific enzymes seem to be in operation.

Effects of selenate supplemented fertilisation on the selenium level of cereals — identification and quantification of selenium compounds by HPLC–ICP–MS

Laboratory experiments were carried out to investigate whether the selenium content of different kinds of cereals grown on Austrian soil could be raised by the application of compound fertilisers containing selenium as selenate. An anion exchange chromatographic system coupled to an HP 4500 inductively coupled plasma mass spectrometer (ICP–MS) was used for the identification and quantification of selenium compounds in cereal samples. The HPLC–ICP–MS system was optimized for the separation of selenite, selenate, selenocystine, and selenomethionine using a Hamilton PRP-X100 column. Separation was obtained, with a 10 mM citrate buffer (pH 5), 2% methanol as mobile phase and a flow rate of 1.5 ml min−1. Four baseline separated chromatographic peaks were obtained within 6 min. The retention behavior of a further five selenium [selenohomocystine (Sehcys), selenocystathionine (Secysta), selenoethionine (Seet), trimethylselenonium iodide (TmSe), and dimethyl(3-amino-3-carboxy-1-propyl)selenonium iodide (DmpSe)] compounds was investigated. Aqueous extraction and enzymatic hydrolysis of the biological materials were also compared with respect to the amount of selenium extracted. In the aqueous extracts only 3–9% of the total concentration of selenium was found. When the cereal samples were exposed to an enzymatic hydrolysis, recovery rates ranging from 80 to 95% were obtained. A major part of the selenate, which had been taken up by the cereals was converted to selenomethionine.

Dietary Arsenic Intake in Taiwanese Districts with Elevated Arsenic in Drinking Water

Inorganic arsenic in dietary staples (i.e., yams and rice) may have substantially contributed to exposure and adverse health effects observed in an endemic Taiwanese population historically exposed to arsenic in drinking water. Observations of this population were used by the U.S. Environmental Protection Agency to derive toxicity values that form the basis for arsenic risk assessment and various regulations in the United States. However, data were previously insufficient to accurately estimate dietary intake. Rice and yam samples collected in 1993 and 1995 from Taiwanese districts with endemic arsenic were analyzed for total arsenic and for inorganic and organic mono and dimethylarsenic. The acid digestion techniques used in the analyses are among the best to preserve organic arsenic in the test sample. Furthermore, concurrent analyses of the proportion of inorganic arsenic in split samples of rice and yams collected in the 1995 investigation were in good agreement, despite using a different digestion me...

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.

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).

A novel arsenic containing riboside (arsenosugar) in three species of gastropod

Abstract Arsenic compounds in three marine gastropods ( Thais bitubercularis, Thais distinguenda, Morula musiva ) from Phuket, Thailand were examined by HPLC using ICP-MS as an arsenic specific detector. Aqueous methanol treatment of the freeze-dried samples (initially 112–339 μg As g −1 dry mass) extracted >96% of the total arsenic. HPLC-ICP-MS of the extracts demonstrated the presence of arsenobetaine (93–95% of total extractable arsenic), arsenocholine (3.1–4.6%), tetramethylarsonium ion (0.21–2.2%), two unknown arsenic compounds (each approx. 0.1%), and an unresolved mixture of arsenic compounds (∼1%). One of the unknowns was identified as a new natural product, the arsenosugar 2′,3′-dihydroxypropyl 5-deoxy-5-trimethylarsonioriboside, by co-chromatography with synthetic material. The presence of these arsenic compounds in the gastropods is consistent with the hypothesis that trimethylated arsenosugars are transformed into arsenobetaine via arsenocholine within animals.

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 highpressure 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 Askg -1 ) but not in any of the cetaceans. The concentration of dimethylarsinic acid ranged from < 0.001 to 0.109mgAskg -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 .

Retention behavior of inorganic and organic selenium compounds on a silica-based strong-cation-exchange column with an inductively coupled plasma mass spectrometer as selenium-specific detector

Abstract The retention behavior of eight selenium compounds (selenous acid, selenic acid, selenocystine, selenohomocystine, selenomethionine, selenoethionine, trimethylselenonium iodide, and dimethyl(3-amino-3-carboxy-1-propyl)selenonium iodide) with aqueous solutions of pyridine (20 mmol/l) in the pH range 2.0–5.7 on a Supelcosil LC-SCX cation-exchange column was investigated. An inductively coupled plasma mass spectrometer was employed as the selenium-specific detector. To increase the nebulization efficiency, the Meinhard concentric glass nebulizer was replaced by a hydraulic high-pressure nebulizer. At pH 5.0, seven selenium compounds could be separated within 400 s, but selenohomocystine and selenomethionine had the same retention time. Selenomethionine can be separated from selenohomocystine with an aqueous solution of pyridine (20 mmol/l) adjusted with formic acid to pH 2.0. At 1 ng Se ml−1, the relative standard deviations (n=5) of the signal area for the eight selenium compounds ranged from 7 to 11%, and at 50 ng Se ml−1 from 0.6 to 2.6%.

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.