Absorptiometric determination of ferrous iron coexisting. With ferric iron with 1, 10-phenanthroline.

Abstract

The absorptiometric method for the determination of iron with 1, 10-phenanthroline has hitherto been applied to total iron after reduction to ferrous state at an optimum pH in acetate buffer solution. The author applied this reagent to the determination of ferrous iron in the presence of a large excess of ferric iron. The procedure is as follows. Dilute a sample solution containing ferric and ferrous iron to approximately 70 ml with water. Add 10 ml of 0.2% 1, 10-phenanthroline and 10 ml of 5% diammonium citrate, and make up to 100 ml with water. After 20 to 90 min measure the absorbance of ferroin developed in the solution at 510 nm against a reference solution containing approximately the same amount of ferric iron as in the sample, previously determined by EDTA titration. According to the recommended method, 50 µg ferrous iron coexisting with up to 2000 µg ferric iron can be determined, and approximately 100 µg of manganese, magnesium, copper, lead, cadmium, zinc, and tin did not interfere with the ferrous determination without adding EDTA or other masking agent. The lower limit of determination was 0.2 ppm and the reproducibility was 5% for 100 µg ferrous iron coexisting with 1500 µg ferric iron in actual samples. © 1978, The Japan Society for Analytical Chemistry. All rights reserved.