Sequential fluorescent determination of copper (II) and cobalt (II) in food samples by flow injection analysis

Copper (II) can react with a new fluorescence reagent, 5-(4-chlorophenylazo)-8-aminoquinoline (APAQCL), forming a fluorescence product only in slightly acidic medium, while the fluorescence product of cobalt (II) with APAQCL forms only in basic medium and in the presence of H2O2. Based on the difference of the reaction between cobalt (II) and copper (II) with APAQCL, a new flow injection method for the sequential determination of cobalt and copper in binary mixtures by use of a fluorimetric detector and APAQCL as reagent was proposed. Linear calibration graphs were obtained over the concentration range 0.010–1.20 (μg/ml) of cobalt (II) and 0.050–5.00 (μg/ml) of copper (II) with the detection limit of 0.0030 (μg/ml) of cobalt (II) and 0.010 (μg/ml) of copper (II), respectively. The applicability of the method to the sequential determination of cobalt (II) and copper (II) in food samples was demonstrated by investigating the potential interference and by the analysis of synthetic mixtures of copper (II) and cobalt (II). The method was successfully applied to the determination of copper and cobalt in food samples.