Direct-injection chemiluminescence detector. Properties and potential applications in flow analysis

• A novel chemiluminescence flow-through detector is proposed.
• A sample and reagents are injected directly into the detector by pulse micro-pumps.
• Chemiluminescence signals are registered immediately after the moment of mixing.
• Kinetic investigations of a fast reaction are possible.
• Sensitive and repeatable determinations with high sampling rate are possible.

We present a novel chemiluminescence detector, with a cone-shaped detection chamber where the analytical reaction takes place. The sample and appropriate reagents are injected directly into the chamber in countercurrent using solenoid-operated pulse micro-pumps. The proposed detector allows for fast measurement of the chemiluminescence signal in stop-flow conditions from the moment of reagents mixing.To evaluate potential applications of the detector the Fenton-like reaction with a luminol-H2O2 system and several transition metal ions (Co2+, Cu2+, Cr3+, Fe3+) as a catalyst were investigated. The results demonstrate suitability of the proposed detector for quantitative analysis and for investigations of reaction kinetics, particularly rapid reactions. A multi-pumping flow system was designed and optimized. The developed methodology demonstrated that the shape of the analytical signals strongly depends on the type and concentration of the metal ions. The application of the detector in quantitative analysis was assessed for determination of Fe(III). The direct-injection chemiluminescence detector allows for a sensitive and repeatable (R.S.D. 2%) determination. The intensity of chemiluminescence increased linearly in the range from about 0.5 to 10 mg L−1 Fe(III) with the detection limit of 0.025 mg L−1. The time of analysis depended mainly on reaction kinetics. It is possible to achieve the high sampling rate of 144 samples per hour.