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This paper reports arsenic speciation in edible seaweed (from the Galician coast, northwestern Spain) produced for human consumption. Chondrus crispus , Porphyra purpurea , Ulva rigida , Laminaria ochroleuca , Laminaria saccharina , and Undaria pinnatifida were analyzed. The study focused on arsenosugars, the most frequently occurring arsenic species in algae. As(III) and As(V) were also determined in aqueous extracts. Total arsenic in the samples was determined by microwave digestion and inductively coupled plasma mass spectrometry (ICPMS). For arsenic speciation, a water extraction especially suitable for arsenosugars was used, and the arsenic species were analyzed by liquid chromatography with both anionic and cationic exchange and ICPMS detection (LC-ICPMS). The total arsenic content of the alga samples ranged from 5.8 to 56.8 mg As kg(-1). The mass budgets obtained in the extracts (column recovery × extraction efficiency) ranged from 38 to 92% except for U. pinnatifida (4%). The following compounds were detected in the extracts: arsenite (As(III)), arsenate (As(V)), methylarsonate (MA), dimethylarsinate (DMA), sulfonate sugar (SO(3)-sug), phosphate sugar (PO(4)-sug), arsenobetaine (AB), and glycerol sugar (Gly-sug). The highest concentrations corresponded to the arsenosugars.

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We present a method for screening lipid-soluble arsenic compounds (arsenolipids) in fish oils by reversed-phase HPLC-ICPMS using a gradient elution with ethanol and acetate buffer at pH 6. Two different approaches were tested to reduce changes in arsenic response due to the carbon effect: addition of a supplementary methanol solution directly to the spray chamber or addition of methanol post-column through a T-piece. The latter method proved to be the best option for maintaining constant response for several arsenolipids covering a wide range of polarities. With the optimized method it is possible to perform a screening of at least three groups of arsenolipids with different polarities in 90 min with detection limits ranging from 5 to 11 mg As L À1 , depending on the analyzed compound. The method was applied to the screening of arsenolipids in fractions obtained from cod liver oil and capelin oil, which include arsenic-containing fatty acids, arsenic-containing hydrocarbons and another group of lower polarity and unknown character.