A luminescence-based scanning respirometer for heavy metal toxicity monitoring

A respirometer has been developed for microbial toxicity tests. The measurement of oxygen concentration in the respirometer is based on luminescence quenching by molecular oxygen. The oxygen-sensing film consists of a luminescent ruthenium complex adsorbed on amorphous fumed silica and immobilized inside silicone rubber. The luminescence intensity depends on the oxygen concentration in the sample in contact with the sensing film. The inhibition effect of heavy metals on the respiration rate of microorganisms can be evaluated by monitoring the luminescence intensity of the sensing film. The toxicity of Cu2+, Zn2+, Ni2+, Cr3+, Pb2+ and Hg2+ on activated sludge was tested using the respirometer. The results indicated that the proposed method is a sensitive method for estimating IC50 (concentration of a toxicant producing 50% respiration inhibition) in microbial toxicity tests. (C) 1996 Elsevier Science Limited