Improved spectrophotometric determination of total iron and iron (III) with o-hydroxyhydroquinonephthalein and their characterization

Abstract

Simultaneous and fractional determination of iron (II) and iron (III) was accomplished with o-hydroxyhydro- quinonephthalein (QP) in the presence of poly (N-vinyl pyrrolidone). In the determination of total iron (iron (II) + iron (III)), Beer's law was obeyed in the range of 0.02-0.67 μg•ml -1, with an effective molar absorptivity (at 570 nm) and a relative standard deviation of 1.30×10 5 1•mol -1•cm -1 and 0.77% (n=8), respectively. This method was about 10-15 times and more than the methods using 1,10-phenanthroline and 2,2'-bipyridine. In addition, the iron-QP com- plex was characterized using spectrophotometry and the electron spin resonance. This method was successfully applied to assays of total iron and iron (III) in pharmaceutical preparations. © 2011 The Pharmaceutical Society of Japan.