Abstract
In this paper we describe a thermal biosensor with a flow injection analysis system for the determination of the chemical oxygen demand (COD) of water samples. Glucose solutions of different concentrations and actual water samples were tested, and their COD values were determined by measuring the heat generated when the samples passed through a column containing periodic acid. The biosensor exhibited a large linear range (5 to 3000 mg/L) and a low detection limit (1.84 mg/L). It could tolerate the presence of chloride ions in concentrations of 0.015 M without requiring a masking agent. The sensor was successfully used for detecting the COD values of actual samples. The COD values of water samples from various sources were correlated with those obtained by the standard dichromate method; the linear regression coefficient was found to be 0.996. 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 biosensor is suitable for the continuous monitoring of the COD values of actual wastewater samples.
Highlights
In recent years, increasing attention has been devoted to the removal of organic contaminants from wastewater
The chemical oxygen demand (COD) is a parameter used widely to determine the amounts of organic pollutants in wastewater
We have developed a thermal biosensor for use in COD determination
Summary
In recent years, increasing attention has been devoted to the removal of organic contaminants from wastewater. The chemical oxygen demand (COD) is a parameter used widely to determine the amounts of organic pollutants in wastewater. The COD is defined as the number of oxygen equivalents consumed in the oxidation of organic compounds by strong oxidizing agents, such as dichromates and permanganates, and is indicative of the amount of organic pollutants present in the tested sample [3]. Conventional methods for determining the dichromate concentration suffer from several inherent drawbacks. They are time-consuming, exhibit low detection sensitivity, involve complex procedures, require the use of expensive (Ag2SO4) and toxic (Cr and Hg) chemicals, and result in the incomplete oxidation of the pollutants [1,4,5,6,7,8,9,10,11]. Secondary pollution is unavoidable when these methods are employed [12]
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