USE OF THE TRIIODIDE HEXADECYLPYRIDINIUM CHLORIDE MICELLAR SYSTEM FOR THE KINETIC DETERMINATION OF MOLYBDENUM(VI)

The associate formed by triiodide ion and hexadecylpyridinium chloride (cetylpyridinium chloride; CPC) micelles was used to enhance the kinetic spectrophotometric determination of Mo(VI) by its catalytic action on the oxidation of iodide with hydrogen peroxide in an acidic medium. The reaction rate was monitored at 500 nm, the maximum absorption wavelength of the I3--CPC associate. The micellar medium allowed the determination of Mo(VI) at concentrations between 2 and 150 ng ml 1, with a detection limit of 1.3 ng ml-1 (i.e., about 6-8 times lower than those of methods implemented in aqueous media). The relative precision achieved for 80 ng ml-1 of Mo(VI) was 2.6%. The selectivity towards interferents, yielding yellowish solutions, was significantly enhanced. The proposed method was applied to the determination of Mo in aqueous extracts of soil samples with no prior separation.