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 usi ng derivative spectrophotometry was developed for the determination of cobalt and iron in mixtures. A conventional two-channel flow injectio n manifold was used to develop the analytical reactions between the an alytes and ferrozine and drive the reaction products to the detector. After the signal (550 nm) reached the maximum the flow was stopped, th e spectrum recorded between 400 and 700 nn and transformed into its fi rst-derivative form using a Delta lambda of 1.6 nn. Cobalt andiron wer e thus determined in the range 1.1-25 mu g/ml and 0.15-6.0 mu g/ml, re spectively. The detection limits were found to be 0.33 mu g/ml of coba lt and 0.045 mu g/ml of iron. The method was applied to the determinat ion of the analytes in water samples.