Determination of mixtures of cobalt and Iron by first derivative spectrophotometry

Abstract

Cobalt and iron can be determined simultaneously by first derivative spectrophotometry. The method does not require simultaneous equations to be resolved and it is based on the separation of the analytes, by liquid-liquid extraction, integrated reaction with 3-(4-phenyl-2-pyridinyl)-1,2,4-triazine, and perchlorate in dichloroethane and on the subsequent derivative spectrophotometric measurement using the graphical and the zero-crossing methods for determination of iron and cobalt, respectively. Cobalt and iron were thus determined in the range 57-1200 ng/ml and 2.0-120 ng/ml, respectively, in the presence of one another. The method has a high sensitivity and the detection limits (3σ) were calculated to be 17.1 ng/ml of cobalt and 0.6 ng/ml of iron. The relative standard deviations were in all instances less than 3.2%. The proposed method was successfully applied to the determination of both analytes in river water