An improved apparatus for on-line chemiluminescence detection with capillary electrophoresis and detection of metal–porphyrins

An improved apparatus for on-line chemiluminescence detection with capillary electrophoresis is proposed. In the present method the grounding electrode of the power was put in the four-way joint, not in the eluate reservoir, and the reaction capillary with greater inner diameter was set at a slope down. The bubbles produced by the breakdown of hydrogen peroxide could therefore be drained out much more easily and did not perturb the separation and detection. Satisfactory reproducibility was still achieved even at a higher concentration of hydrogen peroxide in strongly basic medium. Metal–porphyrins, the sensitive catalysts for luminol chemiluminescence reactions, were measured for the first time by on-line chemiluminescence detection with capillary electrophoresis. The detection limit for 5,10,15,20-tetrakis(4-sulfonatophenyl)-21H,23H-porphine manganese(III) was 361 amol and 8.1 × 10–9 mol L–1. Under the optimized chemiluminescence conditions, Co–meso-tetrakis(4-sulfonatophenyl)porphyrin with limited catalytic efficiency could also be detected with a satisfactory detection limit of 964 fmol and 2.7 × 10–5 mol L–1.