Catalytic determination of iodide using the promethazine–hydrogen peroxide redox reaction

Abstract

A highly selective and sensitive spectrophotometric method was developed for the determination of iodide based on its catalytic effect on the oxidation of promethazine hydrochloride (PM) with H₂O₂. The red oxidation product of PM is monitored at 516 nm for 40 s. Using the recommended procedure, iodide can be determined with a linear calibration graph up to 12 ng ml^–1 at 25 °C. The limit of detection is about 0.1 ng ml^–1. The mechanism of the reaction is inferred. The method was successfully applied to the determination of iodide in river waters.