Comparison of three methods for the extraction of arsenic compounds from the NRCC standard reference material DORM-2 and the brown alga Hijiki fuziforme

The NRCC standard reference material DORM-2 and the marine brown alga Hijik i fuziforme were extracted with water, methanol/water (9 + 1), and 1.5 M or thophosphoric acid. The extracts from DORM-2 were analyzed by HPLC-ICP-MS f or arsenobetaine, arsenocholine, trimethylarsine oxide, and the tetramethyl -arsonium cation and the extracts from H. fuziforme for arsenous acid, arse nic acid, dimethylarsinic acid, methylarsonic acid, and four arsenoriboses. Almost no differences between the three extractants were observed when DOR M-2 was investigated. Only arsenobetaine was slightly better extracted with 1.5 M orthophosphoric acid or methanol/water (9 + 1) than with water. The sum of all extractable compounds (arsenobetaine, the tetramethylarsonium ca tion, and a formerly unknown compound recently identified as the trimethyl( 2-carboxyethyl)arsonium ion) accounted for 94% of the total arsenic when 1. 5 M orthophosphoric acid was used, for 92% when methanol/water (9 + 1) was used, and for 87% when water was used. Significant differences in the extra ction yields obtained for the alga were observed for arsenic acid and one o f the arsenoriboses ('glycerol-ribose'). Orthophosphoric acid removed twice as much of this ribose from the algal material than water and three times more than methanol/water (9 + 1). Arsenic acid was 1.2 times better extract ed with orthophosphoric acid than with water and ten times better than with methanol/water (9 + 1). Almost no differences in the extraction yields wer e found for dimethylarsinic acid and the other three riboses. Orthophosphor ic acid extracted 76%, water 65%, and methanol/water 33% of the total arsen ic from H. fuziforme. Copyright (C) 2001 John Wiley & Sons, Ltd.