Abstract：In the medium of sulfuric acid and hexadecylpyridinium bromide micelle，trace bismuth （Ⅲ） has inhibitory effect on the reaction between coomassie brilliant blue and hydrogen peroxide. Therefore, a new inhibitory kinetic spectrophotometry for the determination of trace bismuth （Ⅲ） was established. The effects of these factors were discussed, such as surfactant, reaction medium and its dosage, reagent dosage, heating time, heating temperature and interference ions. Under the optimum conditions, the absorbance difference between inhibition system and non-inhibition system at 600 nm showed good linearity to the concentration of bismuth （Ⅲ） in the range of 0.8-112 μg/L. The detection limit of this method was 9.37×10-7 g/L. The catalytic reaction was the zero-order reaction with apparent activation energy of 142.14 kJ/mol and reaction rate constant of 4.1×10-3 mol/L·s. The sensitivity was increased by five times than in the absence of CPB. The method has been used in the determination of bismuth （Ⅲ） in water and alloy samples, and the results were consistent with those obtained by atomic absorption spectrometry.
