Spectrophotometric Determination of Iron(Ⅲ) after Separation by Adsorption of its pyrrolidinedithiocarbamate on Naphthalene

A method is presented for the spectrophotometric determination of trace amounts of iron(Ⅲ) after adsorption of its pyrrolidinedithiocarbamate with microcrystalline naphthalene. Iron(Ⅲ) forms a stable chelate with pyrrolidinedithiocarbamate ammonium salt and this chelate is quantitatively adsorbed onto microcrystalline naphthalene at room temperature in the pH range of 2.9-6.6. The mixture of the chelate and naphthalene is dissolved in chloroform. The chelate in naphthalene-chloroform solution obeys Beer's law over the range 2.3-49 μg of iron(Ⅲ) in 10 ml of chloroform. The molar absorptivity is 1.1 x 104 l.mol-l・cm-l at 357 nm, the sensitivity being 4.9 x 10-3 μg/cm2 for the absorbance of 0.001. The relative standard deviation for the present analysis of iron(Ⅲ) is 1.0% for ten determinations. In the present experiments, the effect of variables such as pH, amounts of reagent and naphthalene, digestion and shaking time and diverse ions have been examined. The method has been applied to the determination of iron(Ⅲ) in reference and environmental samples and results compared with l,lO-phenanthroline method