New Induction Period Based Kinetic Spectrophotometric Method for the Determination of Iron (II) in Pharmaceutical Products

A new simple, sensitive and selective kinetic spectrophotometric method was developed for the determination of iron (II) in pharmaceutical products. The method is based on the enhancing effect of iron (II) on the sodium periodate-potassium bromide-meta cresol purple reaction system in the presence of thiocyanate. The reaction starts after an induction period, which decreased by addition of iron (II). The reciprocal of the reaction induction period is proportional to the iron (II) concentration. The decolorization of meta cresol purple (MCP) at 525 nm was used to monitor the reaction spectrophotometrically. Under optimum conditions, iron (II) can be determined in the range of 0.020–4.0 μg mL–1 with a 3o detection limit of 0.017 μg mL–1. The relative standard deviations for five replicate determinations of 0.030, 0.20, and 2.0 μg mL–1 iron (II) were 2.9%, 2.7% and 2.3%, respectively. This method was successfully used in the determination of iron (II) in ferrous sulfate pharmaceutical products.