Determination of iodate ion in the presence of hydrogen peroxide with the stopped-flow technique

Abstract

The modified titration of iodate and hydrogen peroxide with iodide in acidic medium was investigated in order to study the possibility of separation and determination of iodate under certain conditions. The stopped-flow technique was used to kinetically distinguish titration products ${\text{I}}_{ 2}$ and ${\text{I}}_{3}^{ - }$ formed in both reactions. Under the given conditions, the reaction between iodate and iodide is finished considerably faster than the reaction between peroxide and iodide. For the ratio [KIO₃]/[H₂O₂] ≈ 0.08 and acidity of [H₂SO₄] = 1.005 × 10⁻¹ M, the kinetic separation between both components may be achieved to within 0.3 %, in less than 3 s. The recovery value of the iodate, with the applied technique after completion of the reaction, is ≈98 % showing appropriately chosen reaction conditions. Our results show that when iodate–iodide and peroxide–iodide reactions occur simultaneously under certain conditions, the contribution of peroxide–iodide products may be neglected. It was shown that stopped-flow titration of iodate in specific reactions and certain iodate/peroxide ratio may be used for determination of iodate concentration within a few percent.