A New Spectrophotometric Method for Determination of Iron in Herbs, Spices and Beans with 2,6-Diacetylprydine Dioxime and 2-Acetylpyridine Monoxime

The reaction of iron (II) with 2, 6-diacetylprydine dioxime (H2dapd) and 2-acetylprydine monoxime (Hapm) in 10% and 60% v/v ethanol-water solution at pH 2.5 and 7.5, respectively, were studied using direct and first derivative spectrophotometry. Fe (III) is reduced by H2dapd and gives iron (II) complex. A simple, rapid, selective and sensitive method for the determination of Fe (II), Fe (III) and a mixture of them with the H2dapd reagent in acid water-ethanol medium after the solution attained to stand periods of 30 sec, 4 hr and 4 hr, respectively, are proposed. Hapm also reacts with Fe (II) to form [Fe(Hapm)3] 2+ complex with less selectivity and sensitivity than H2dapm reagent. Calibration graph with [Fe(H2dapd)2] 2+ is linear over the range 0.28 μg mL ̄ with an apparent molar absorptivity of 8.481×10 L mol ̄cm ̄ at λm 428 nm. Linear dynamic ranges are 0.01-11.0 and 0.0711.0 μg mL ̄ iron (II) as [Fe(H2dapd)2] complex for direct and derivative modes, respectively. The analytical sensitivity is 4.44×10 μg mL ̄ for direct and 9.15×10 μg mL ̄ for derivative spectrophotometry with [Fe(H2dapd)2] 2+ complex. First derivative method enhances the sensitivity of the Fe(H2dapd)2] 2+ more than direct one with two folds for Ni, Co, Cu and Cr. A linear equation was derived from iron (II) determining as Fe (H2dapd)2] 2+ in the presence of synthetic solution containing Ni, Co, Cu and Cr. The use of H2dapd reagent for the determination of total iron spectrophotometerically in foodstuffs, herbs, spices (rocks) after wet ashing (wet digestion) in the absence of reducing agent is compared with that employing AAS.