Abstracts: ISEE 21st Annual Conference, Dublin, Ireland, August 25-29, 2009: Symposium Abstracts
Background and Objective:
Consumption of seaweed has recently increased as a diet food in Western countries. Edible brown alga (hijiki; hijikia fusiforme) contains not only a high content of inorganic arsenic (iAs) but also various kinds of arsenosugars (AsSug) which are metabolized to dimethylarsinic acid (DMA) in mammals. Since DMA is considered to be tumorogenic in rodents, it is necessary to accurately measure the contents of AsSugs as well as iAs for the risk assessment of seaweed consumption.
Nine kinds of dried hijiki products were provided for analysis. Total arsenic (T-As) was measured by DRC-ICP/MS after wet-digestion. After water-extraction, speciation analysis of arsenics was performed by HPLC-ICP/MS using PRP-X100 anion exchange column with mobile phase of 20 mM NH4HCO3 and detection mass of m/z 75 (75As+), 72 (72Ge+), and 35 (35Cl+). AsSugs were detected by HPLC-MS/MS with multiple-reaction monitoring in the positive ion mode.
The ranges of T-As, water soluble total As and water soluble iAs concentrations in nine hijiki samples were 37.1–118.6, 20.0–81.6, 9.2–55.8 μgAs/g dry weight, respectively. The ratio of iAs to T-As ranged from 24.5 to 60.1%. The major compound detected was arsenate in all samples and the concentrations ranged 8.9–70.5 μgAs/g dw. Five kinds of oxo-AsSug were detected in eight of nine samples. The peak of dimethylarsenosugarsulfate (MW = 408) was higher than any other oxo-AsSugs. The content ratio of AsSugs to T-As ranged from 6.8∼52.5%.
The contents of T-As, iAs and AsSug varied with hijiki products. Five kinds of oxo-AsSug were detected by HPLC-MS/MS, which was much more highly sensitive than HPLC-ICP/MS. Since iAs could not be detected by HPLC-MS/MS, combination analysis of HPLC-MS/MS and HPLC-ICP/MS would be necessary for determination of arsenic speciation in seafood.