Determination of Ultrance Amounts of Iron in Concentrated Acids by Flow Injection Spectrophotometric Method Based on the Catalytic Effect of Iron Ion on the Oxidation Reaction of N,N-dimethyl-p-phenylenediamine with Hydrogen Peroxide

Abstract

A spectrophotometric flow injection system is described for the determination of iron in acid samples. The detection method is based on the catalytic action of iron(III) on the oxidation reaction of N,N-dimethyl-p-phenylenediamine (DPD) in the presence of hydrogen peroxide. An increase in absorbance of oxidized DPD was measured spectrophotometrically at 514 nm. The proposed method allows the dynamic linear calibration of 0.1 to 1.0 µg L^-1 of iron. The method showed high sensitivity (LOD 0.008 µg L^-1) with good repeatability (RSD below 2%). And was also successfully applied to the determination of ultratrace amounts of iron in commercially available concentrated acids, such as hydrochloric, sulfuric and acetic acid.