INDIRECT KINETIC SPECTROPHOTOMETRIC DETERMINATION OF COBALT BASED ON THE REDOX REACTION WITH IRON(III) IN THE PRESENCE OF 1,10-PHENANTHROLINE

Abstract

ABSTRACT An indirect kinetic spectrophotometric method is presented for determina tion of trace amounts of cobalt. The method is based on the redox reaction of cobalt with Fe(III) in the presence of 1,10-phenanthroline. In the presence of 1,10-phenanthroline, Fe(III) is reduced easily by cobalt(II) to a Fe(II)-1,10 phenanthroline complex,which shows an absorp tion maximum at 514 nm. Linear calibration graphs were obtained over the range 0.25–12 µg mL−1 of cobalt. The detection limit was 0.2 μg mL−1 of cobalt. The relative standard deviation for the determina tion of 0.5 μg mL−1, 2 μg mL−1 and 5 μg mL−1 cobalt (n=8) were 1.4%, 0.6% and 0.8%, respectively. The method is free from most interferences, especially from Fe(II). The proposed method was successfully applied to the determination of cobalt in synthetic alloy solutions.