Abstract: A new resonance light scattering (RLS) method for the determination of trace iodine was developed based on the principle of I (Ⅴ) reacting with excessive potassium iodide and cetylpyridimium bromide to form an ion-associated complex (1:1) in the presence of 0.03 mol/L H3PO4, thus resulting in an obvious enhancement of RLS. Reaction conditions including acidity, reagents dosage, reaction temperature and reaction time were optimized. An excellent linear relationship between the enhanced RLS intensity and I (Ⅴ) concentration was achieved in the range of 0.02－0.4 μg/mL with the maximum RLS peak wavelength at 469 nm. The detection limit was 0.033μg/L. The method was applied to the determination of iodine in refined sea salt, laver and kelp samples. The results were in good agreement with those obtained by iodimetry. The relative standard deviation was 0.7%－1.2% (n＝5), and the recovery rate was 98.4%－101.5%.

Key words: iodine, resonance light scattering, potassium iodide, cetylpyridimium bromide, food