Abstract
A precision determination method of iron based on the formation of a stable iron complex was investigated by flow injection analysis (FIA). Four significant figures on the Fe content (%) could be obtained as the result of analysis by the present method, which was applied to the determination of iron in iron ores. Besides high precision, the results of Fe determination in standard iron-ores samples showed good agreement with certified values. The precision of the present method was equal to that of titration as the conventional method. The Fe complex formed in a line reaction tube with 1,2-dihydroxybenzene-3,5-disulfonic acid (Tiron) was detected by spectrophotometry at 667 nm. Tiron as the optimum detection reagent was selected based on the complex stability examined by using a stopped flow-meter, which could measure the absorbance with 6 significant figures, from among 4 kinds of conventional detective reagents. The absorbance obtained by UV-Vis spectrophotometry was recorded with 6 significant figures by Chromatomoniter with a personal computer. The channel flow system was examined concerning 4 kinds of manifold on the precision of the signal peak height and area. As a result, a single flow system was selected as the optimum manifold. A calibration curve was constructed by measuring the peak height of the absorbance signal. The optimum conditions of iron determination by the present method were as follows: sample solution (29.4 μl), pH 1.0; Tiron, 8.0 × 10−3 M, pH 5.0; flow rate, 0.5 ml/min; reaction coil length, 10 m; pump, double-plunger pump. A damper was used between the pump and the sample injector. The iron was determined over the range of 10 to 300 ppm by measuring a 1 : 1 complex of iron -Tiron. The RSD was 0.07% in the range of 150 to 300 ppm. The present method could be applied to iron ores containing above 55% iron. The throughput per hour was 6 for the sample solution.
