Abstract: Tungsten(Ⅵ)and molybdenum(Ⅵ)have similar catalytic behavior and they all have catalytic effects on the oxidation of iodide by hydrogen peroxide in acidic medium.There is, however, different inhibition in the catalytic activity of each catalyst in the presence of suitable organic reagents.In this paper, two equal sets of standard mixtures of tungsten(Ⅵ)and molybdenum(Ⅵ)were used as the catalysts in the experiments with and without the presence of Organic reagents, respectively.The reaction rate was measured potential by an iodic ion selective t3lectrode.Two multivariate calibration models, linear and nonlinear, were then developed.The catalytic behavior of tungsten(Ⅵ)and molybdenum(Ⅵ)in the presence of different organic acids(citric, tartaric, oxalic and malonic)was investigated.The two calibration models were successfully applied to the prediction of unknown samplesof trace tungsten(Ⅵ)and molybdenum(Ⅵ)in the range of 0.012-0.20μg/mL.

Key words: Kinetic-catalytic method, Tungsten and molybdenum, Multivariate calibration, Simultaneous determination, Iodic ion seiective electrode