EVIDENCE OF THE PRESENCE OF DIMETHYLATED, TRIMETHYLATED AND REFRACTORY ARSENIC COMPOUNDS IN ESTUARINE SALT-MARSH HALOPHYTES

Five species of halophytes were sampled in the salt marshes of the Tag us estuary, dried, ground and digested. They were further extracted wi th ethanol and the extracts passed through weak and strong cationic io n-exchange resins, purified through TLC and submitted to pyrolysis mas s spectrometry and HPLC-ICP/MS. Arsenic content and hydride-forming ar senic species were verified, in each step, by GF-AA and HG-QFAA. A hig h content of arsenic was found in the samples of halophytes studied, b oth di- and tri-methylated arsenic compounds being present. A consider able fraction of this arsenic content seems to be refractory to hydrid e generation. Moreover, the arsenic fraction found seems to have the s ame ion-exchange behaviour as the refractory fractions formerly studie d in estuarine water. A partial characterization of these structures b y pyrolysis-GC-MS suggests the presence of arsenobetaine and arsenocho line compounds. Furthermore, HPLC-ICP/MS data seem to confirm the pres ence of these compounds. In addition, the latter hyphenated technique strongly suggests the presence of a number of other organoarsenicals i ncluding tetramethylarsonium (TMAs), trimethylarsine oxide (TMAO), cac odylate (DMA) and possibly an arsenosugar-type compound. (C) 1997 by J ohn Wiley & Sons, Ltd.