[Determination of trace molybdenum by extraction catalytic kinetic spectrophotometry]

A new extraction catalytic kinetic spectrophotometric method for the determination of trace molybdenum is studied. The method is based on the molybdenum (VI) catalytic oxidation of o-aminophenol by hydrogen peroxide in week acidic medium at pH 5.5. The reaction is carried out at room temperature. The reaction time, concentration of o-aminophenol in aqueous phase and degree of reaction are controlled by extraction equilibrium. The absorbance of organic phase is measured at 424 nm. Under the optimum experiment conditions, the linear range of the determination is 0.0050-2.0 mg.L-1, the detection limit is 2.0 x 10(-6) g.L-1. Combining with separation of ionic exchange, the method has been applied to the determination of trace molybdenum in bean samples with satisfactory results. The kinetic equation of extraction catalytic reaction is discussed.