Simultaneous determination of micro bromide and iodide by kinetic spectrophotometric method

A new kinetic spectrophotometric method for the simultaneous determination of concentrations of micro bromide and iodide has been proposed. It is base d on their catalytic effects on the reaction of m-cresol purple oxidized by potassium periodate in hydrochloride acid medium. The reaction rate was mo nitored by measuring the decrease in absorbance at 528nm and the increase i n absorbance at 455nm. The total difference in absorbance of the sum of bro mide and iodide is identical with determination of bromide was carried out after Cr(VI) oxidized I- to I-2, and I-2 was removed by extraction with CCl 4, and the amount of iodide was measured by subtracting the absorbance chan ge of bromide from the total absorbance change in the presence of bromine a nd iodide. The optimum conditions influencing the reaction rate were studie d. The linear range of determination is 0 similar to 4.0 mu g/ml for Br- an d 0 similar to 3.0 mu g/ml for I-. The detection limits are 0.032 mu g/ml f or Br- and 0.059 mu g/ml for I-. The method was successfully applied to the determination of micro amounts of bromide and iodide in food and life samp les.