Abstract: A new resonance light scattering (RLS) method for the determination of trace zinc in food was developed based on the reaction of Zn2+ with phen and bright yellow in ammonium chloride-ammonia buffer solution at pH 8.5, resulting in a great enhancement of RLS. The best results for zinc determination were achieved by using a reaction system made up of 1.0 mL of ammonium chloride-ammonia buffer solution at pH 8.5, 1.5 mL of 1.0 × 10-4 mol/L phenanthroline solution and 0.8 mL of 5.0 × 10-5 mol/L bright yellow in a 10-mL colorimetric tube for a reaction duration of 4 min at 30 ℃. Maximum RLS peak was observed at the wavelength of 359.4 nm. There was a good linear relationship between RLS intensity and zinc concentration in the range of 0－10μg/L. The limit of detection of the method was 0.11μg/L. The relative standard derivations for 5 replicate determinations of banana, cucumber and laver by the method were between 0.96% and 1.71%, and the average spike recovery rates between 98.00% and 102.67%. The method was applicable to determine zinc content in banana, cucumber and laver with results consistent with those obtained by atomic absorption spectrometry.

Key words: zinc, resonance light scattering, phen, bright yellow, food