On-line speciation analysis of arsenic compounds in commercial edible seaweed by HPLC-UV-thermo-oxidation-HG-AFS.

Arsenic speciation analysis in dried seaweeds was carried out using an on-line HPLC-UV-thermo-oxidation-HG-AFS system. Species separated and quantified were: arsenite [As(III)], arsenate [As(V)], monomethylarsonic acid (MMA), dimethylarsinic acid (DMA) and different arsenosugars. Extraction efficiency ranged between 38 and 83%. Chromatographic separation was achieved in gradient elution mode using (NH4)2CO3 as mobile phase in the pH range 9-10.3. Total As concentration was quantified by ICP-MS after microwave digestion. Limits of detection were in the range 3.0 to 6.0 ng g-1 for the species under study based on peak height and the relative standard deviation was <8% at 10 µg L-1 As. The accuracy of the procedure was verified by analyzing the CRM BCR-279 Ulva lactuca. Results for total As were in agreement with the certified values. The HPLC-(UV)-HG-AFS system resulted suitable for quantification of eight As compounds. Results showed that arsenosugars are the most abundant compounds in the investigated seaweeds.