A kinetic spectrophotometric method for the determination of iron (III) in water samples

Abstract

A new kinetic spectrophotometric method has been developed for the determination of iron (III). The method is based on the catalytic effect of iron (III) on the oxidation of weak acid brilliant blue dye (RAWL) by KIO₄ in acid medium. The advantages of the proposed method are that it is sensitive, accurate, rapid, inexpensive, can be operated under room temperature and has a large determination concentration range compared to other techniques. The obtained optimum conditions are: pH 3.15, RAWL (200 mgL⁻¹) 5.00 mL, Potassium periodate solution (0.01 molL⁻¹) 0.30 mL, phenanthroline (0.02 molL⁻¹) 1.00 mL, reaction temperature 25°C and reaction time 7 min. With this method iron could quantitively be determined in the range 0.00–0.02 mgL⁻¹, the detection limit being 4.10 × 10⁻¹⁰ g mL⁻¹. The relative standard deviations (RSD) in five replicate determinations for 3 µgL⁻¹ and 5 µgL⁻¹ iron (III) are 3.1% and 1.9%, respectively. The method has been applied to the determination of iron (III) in tap water samples and seawater samples (from the South China Sea), the recovery rates being 98.0% and 100.5%, respectively.