Arsenic Compounds in Terrestrial Organisms II: Arsenocholine in the MushroomAmanita 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.