Simple, Rapid, and Precise Determination of Manganese in Iron and Steel by Flow-injection Analysis

In order to improve the simplicity, rapidity, accuracy and precision in the chemical analysis of iron and steel, a flow-injection analysis (FIA) has been studied for manganese determination with photometric detection. The FIA system consists of a direct on-line coupling of coloring reaction and absorbance measurement in a continuous flow mode ; manganese is oxidised by ammonium peroxodisulfate to MnO4- and the absorbances of the resultant solution are measured before and after the addition of sodium nitrite. The FIA manifold and the optimum reaction conditions were established for allowing this simultaneous measurements of analytical and blank signals by single sample injection with single detector. The analytical results by the proposed method for four Japanese standards of steel (The Iron and Steel Institute of Japan) agreed well with the certified values for manganese and showed high precision of relative standard deviations of 0.25-0.50% which are much smaller than those usually observed in manually operated spectrophotometric methods. An injection rate of 12 sample solutions/h can be achieved. The most appealing feature of the proposed method is that the analysis is achieved in a continuous and nearly closed system without complicated manual operations, which can afford simpler and rapid as well as accurate and precise determination of manganese.