Flow injection (FI) has been applied to the determination of Cr(III) i
n water and food samples. The method is based on measurement of the li
ght emitted from the Cr(III)-catalysed oxidation of luminol by H2O2. T
he apparatus consists of an FI system with a flow cell suitable for ch
emiluminescence detection. The flow cell, situated near the photodetec
tor, is a coiled tube made from transparent poly(tetrafluoroethylene.
The typical signal is a narrow peak, the height of which is proportion
al 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 w
ere optimized. Interferences by several metal ions were examined, and
the system was shown to possess a high selectivity. The method was suc
cessfully applied to the determination of Cr(III) in water and food sa
mples.