Rapid determination of o-phenylenediamine of water using an enzyme thermistor

In this paper, we describe an enzyme thermistor with a flow injection analysis system for the determination of o-phenylenediamine (OPD) in water samples. O-phenylenediamine solutions of different concentrations and actual water samples were tested, and their OPD values were determined by measuring the heat generated when the samples passed through an enzyme column containing horseradish peroxidase and hydrogen peroxide. The biosensor exhibited a large linear range (1 to 1000 mu M) and a low detection limit (1.99 mu M). The thermal sensor was successfully used for detecting the OPD values of actual water samples. The OPD values of water samples from various sources were correlated very well with those obtained by the reference method; the relative standards were less than 5%. The sensor is environmentally friendly, economical and highly stable, and exhibits good reproducibility and accuracy. In addition, its response time is short, and there is no danger of hazardous emissions or external contamination. Finally, the samples to be tested do not have to be pretreated. These results suggest that the enzyme thermistor is suitable for the continuous monitoring of the OPD values of actual wastewater samples.