Analysis of Inorganic and Organic-Bound Arsenic in Marine Brown Algae

Abstract

Inorganic arsenic in brown algae was removed by distillation as the corresponding trichloride and assessed by absorption of the arsine-silver diethyldithiocarbamate complex. Severe digestion conditions for organic-bound arsenic were found necessary to determine total arsenic analyzed subsequently by the silver diethyldithiocarbamate-pyridine reagent. Arsenic in the inorganic and organic forms ranged from 0.5-2.7 and 40.3-89.7 .mu.g g-1 dry wt, respectively, in 7 spp. of the Laminariaceae, [Agarum fimbriatum, Costaria costata, Cymathere triplicata, Hedophyllum, sessile, Laminaria groenlandica, L. saccharina, L. setchellii], 3 spp. of the Alariaceae [Alaria nana, Egregia menziesii, Pterygophora californica] and Lessoniaceae [Canada] [Nereocystis luetkeana, Macrocystis integrifolia, Lessoniopsis littoralis] collected in British Columbia [Canada]; providing levels of inclusion similar to commercially available brown seaweed products. By contrast Sargassum muticum contained 20.8 .mu.g g-1 dry wt of inorganic arsenic, about 38% of the total concentration, and a commercial specimen of Hizikia fusiforme contained 71.8 .mu.g g-1 inorganic aresenic, some 58% of the total concentration, suggesting the propensity of members of the Sargassaceae family to accumulate the inorganic form of arsenic.