FLOW-INJECTION CHEMILUMINESCENCE METHOD FOR THE SELECTIVE DETERMINATION OF CHROMIUM(III)

Flow injection (FI) has been applied to the determination of Cr(III) in water and food samples. The method is based on measurement of the light emitted from the Cr(III)-catalysed oxidation of luminol by H2O2. The apparatus consists of an FI system with a flow cell suitable for chemiluminescence detection. The flow cell, situated near the photodetector, is a coiled tube made from transparent poly(tetrafluoroethylene. The typical signal is a narrow peak, the height of which is proportional to the light emitted and, therefore, to the concentration of Cr(III). The detection limit is 0.01 ppb and the linear range extends up to 6 ppb. The concentrations of the reagents, the pH and the flow rates were optimized. Interferences by several metal ions were examined, and the system was shown to possess a high selectivity. The method was successfully applied to the determination of Cr(III) in water and food samples.