Determination of arsenic in algae - Results of an interlaboratory trial: Determination of arsenic species in the water-soluble fraction

Seven algae samples, five purchased from food stores and two reference algae (BCR 279 Sea Lettuce) were distributed as blind samples to 13 laboratories from which five labs attempted a full characterisation of the water-soluble fraction with respect to their arsenic species. The extraction efficiency is largely dependant on the algae and varied from 3% to 96%. Besides inorganic arsenic (mainly as As-(V) DMA((V))) and, in particular, several arsenosugars were identified in all samples. From the five labs, three labs gave agreeable results in respect of the arsenic species identification and its quantification, although different chromatographic methods were used. Different Hijiki samples seem to contain largely different arsenic concentration (67-113 mg As/kg) which may also have an influence on the distribution of inorganic arsenic and arsenosugars.