CATALYTIC KINETIC SPECTROPHOTOMETRIC DETERMINATION OF TRACE AMOUNTS OF IODINE

A new catalytic kinetic spectrophotometric method has been established for the determination of iodine using the principle that potassium periodate oxidize rhodamine B (RhB) to discolor and I- has a catalytic effect on the reaction. The maximum absorption peak of I--RhB-KIO4 system locates at 556nm in the medium of 0.16mol/mL phosphorus acid. The absorbance difference (A) is linearly related with the concentration of iodine in the range of 0-2.6 mu g/mL and fitted the equation A=0.1578 C(C: g/mL)+0.0052, with a regression coefficient of 0.9965. The detection limit of the method is 7.10ng/mL. The method was used to determine iodine in kelp, potato, tap water, and rain water samples. The relative standard deviation of 13 replicate determinations was 1.81-2.10%. The recovery of the standard addition of the method was 96.2-99.2%.