A flow injection system for spectrophotometric catalytic determination of copper in plant digests and natural waters

The Cu(II)-catalyzed oxidation of 2,6-dichlorophenolindophenol (DCPI) in the reduced form by hydrogen peroxide was exploited for the development of a flow injection procedure for copper determination in plant digests and natural waters. For selectivity enhancement, a Chelex-100 resin mini-column (50-100 mesh) was incorporated to the manifold. The proposed system is very stable, handles about 60 samples per hour, yields precise results (RSD<2% within 5.0 and 70.0 mu g l(-1) Cu) and requires only 0.87 mg DCPI per measurement. Beer's law is followed up to about 100 mu g l(-1) Cu and the detection limit is 0.09 mu g l(-1) Cu (in the injectate). Baseline drift was not observed during extended (5 h) operation periods. Results were in agreement with certified values of standard reference materials and recoveries within 95 and 104% were found.