Identification of arsenobetaine and a tetramethylarsonium salt in the clam <i>Meretrix lusoria</i>

Abstract

Abstract Chemical forms of arsenic were examined in six tissues (gill, mid‐gut gland, siphon, foot, mantle and adductor muscle) of the clam Meretrix lusoria . The gill was found to contain higher levels of arsenic than the other tissues. Regardless of the nature of the tissues, the presence of arsenobetaine was established by HPLC0ICP; it was a minor arsenic compound in gill but a major one in the other tissues. The major arsenic compound in gill, which was more cationic than arsenobetaine, was obtained in a relatively pure state by ion‐exchange chromatography, gel filtration and HPLC. It was positive to the Dragendorff reagent and iodine vapor but negative to ninhydrin reagent. Its 1 HNMR spectrum exhibited only one signal at δ 1.7 (singlet) and its FAB mass spectrum gave a base peak at m/e 135 [(CH 3 ) 4 As + ] and two significant peaks at m/e 120 [(CH 3 ) 3 As] and 106 [(CH 3 ) 2 AsH]. These results suggested that the major arsenic compound in gill exists as a tetramethylarsonium salt (CH 3 ) 4 As + · X − . The tetramethylarsonium salt was also found as a minor component in the tissues other than the gill.