Extraction and detection of arsenicals in seaweed via accelerated solvent extraction with ion chromatographic separation and ICP-MS detection

An accelerated solvent extraction (ASE) device was evaluated as a semi-auto mated means of extracting arsenicals from ribbon kelp. The effect of the ex perimentally controllable ASE parameters (pressure, temperature, static tim e, and solvent composition) on the extraction efficiencies of arsenicals fr om seaweed was investigated. The extraction efficiencies for ribbon kelp (a pproximately 72.6%) using the ASE were fairly independent (< 7%) of pressur e, static time and particle size after 3 ASE extraction cycles. The optimum extraction conditions for the ribbon kelp were obtained by using a 3 mt AS E cell, 30/70 (w/w) MeOH/H2O, 500 psi (1 psi = 7 KPa), ambient temperature, 1 min heat step, 1 min static step, 90% vol. flush, and a 120 s purge. Usi ng these conditions, two other seaweed products produced extraction efficie ncies of 25.6% and 50.5%. The inorganic species present in the extract repr esented 62.5% and 27.8% of the extracted arsenic. The speciation results in dicated that both seaweed products contained 4 different arsenosugar, DMA ( dimethylarsinic acid), and As(V). One seaweed product also contained As(III ). Both of these seaweed products contained an arsenosugar whose molecular weight was determined to be 408 and its structure was tentatively identifie d using ion chromatography-electrospray ionization-mass spectrometry/mass s pectrometry (IC-ESI-MS/MS).