Continuous flow injection reaction/stopped flow detection using derivative spectrophotometry. Determination of cobalt and iron in mixtures

A continuous flow injection reaction-stopped flow detection method using derivative spectrophotometry was developed for the determination of cobalt and iron in mixtures. A conventional two-channel flow injection manifold was used to develop the analytical reactions between the analytes and ferrozine and drive the reaction products to the detector. After the signal (550 nm) reached the maximum the flow was stopped, the spectrum recorded between 400 and 700 nn and transformed into its first-derivative form using a Delta lambda of 1.6 nn. Cobalt andiron were thus determined in the range 1.1-25 mu g/ml and 0.15-6.0 mu g/ml, respectively. The detection limits were found to be 0.33 mu g/ml of cobalt and 0.045 mu g/ml of iron. The method was applied to the determination of the analytes in water samples.