Manganese (II)–1,10‐Phenanthroline–Azo Dye–Potassium Periodate System for Kinetic Spectrophotometric Determination of Nanogram Levels of Manganese

Abstract

The catalytic effect of manganese (II) on the oxidation of the azo dye 3‐methyl‐6‐(2‐hydroxyethoxy)‐2‐[4‐N(N‐methyl‐N‐phenylamino) phenylazo] benzothiazolium methylsulphate, with potassium periodate in the presence of 1,10‐phenanthroline in weakly acidic media is studied. The reaction is followed spectrophotometrically by measuring the decrease in the absorbance of the dye at 610 nm. Under the optimum conditions (1 × 10⁻⁴ mol dm⁻³ azo dye, 1 × 10⁻³ mol dm⁻³ potassium periodate, 4 × 10⁻⁴ mol dm⁻³ 1,10‐phenanthroline, 0.1 mol dm⁻³ buffer–pH 3.0, 70°C, 7 min) manganese (II) in the range 0.1–5 ng cm⁻³ can be determined by the fixed‐time method with a detection limit of 0.035 ng cm⁻³. The developed method is highly sensitive, selective, and simple. The method was applied successfully to the determination of manganese in peas, carrots, and peppers.

Keywords:

• Manganese (II)
• Kinetic determination
• Azo dye oxidation
• Vegetables