Highly sensitive analysis of iodide anion in seaweed as pentafluorophenoxyethyl derivative by capillary gas chromatography.

A simple and sensitive gas chromatography (GC) method is described for the trace analysis of iodide anion (iodide) in processed seaweed as an organic derivative. The method is based on the derivatization of aqueous iodide extracted from seaweed with 2-(pentafluorophenoxy)ethyl 2-(piperidino)ethanesulfonate in toluene using tetra-n-hexylammonium bromide as a phase-transfer catalyst. The resulting pentafluorophenoxyethyl iodide is highly responsive to an electron-capture detector (ECD) and was analyzed by GC-ECD, giving a low detection limit of approximately 2.7 nM (2.7 fmol/microL injected). Interferences of some common anions in the analysis of iodide were studied and proved to be minimal. Application of the method to the analysis of iodide in processed seaweed was performed.