Spectrophotometric Determination of Iron (III) Using 3-Hydroxy-2-Methyl-1,4-Naphthoquinone Monoxime (HMNQM)

Iron (III) forms brown coloured complex with 3-hydroxy-2-methyl-1,4-naphthoquinone monoxime. The iron (III)-HMNQM complex is found to be soluble in DMF and exhibits maximum absorption at 470 nm in the pH range 4.5–5.5. Beer's law is obeyed upto 5.58 ppm of iron (III) and sensitivity of the reaction is 0.0046 μg/cm², with molar absorptivity of 1.21×10⁴ ? mole^?1 cm^?1. The method has been used for the determination of iron (III) in alloys.