A new HPLC method for the detection of iodine applied to natural samples of edible seaweeds and commercial seaweed food products

Rich in micronutrients and considered to contain high iodine levels, seaweeds have multiple applications as food/supplements and nutraceuticals with potential health implications. Here, we describe the development and validation of a new analytical method to quantify iodine as iodide (I−) using an isocratic HPLC system with UV detection; algal iodine was converted to I− via dry alkaline incineration. The method was successfully applied to 19 macroalgal species from three taxonomic groups and five commercially available seaweed food products. Fesh kelps contained highest levels, reaching >1.0% per dry weight (DW), but concentrations differed amongst thallus parts. In addition to kelps, other brown (Fucales: ∼0.05% DW) and some red species (∼0.05% DW) can also serve as a rich source of iodine; lowest iodine concentrations were detected in green macroalgae (∼0.005% DW), implying that quantities recommended for seaweed consumption may require species-specific re-evaluation to reach adequate daily intake levels.