Microbial electrochemical biosensor for rapid detection of naphthenic acid in aqueous solution

Abstract

Abstract In processed water generated from oil sands operations, naphthenic acids (NAs) are identified as one of the primary sources of acute toxicity and were assessed for their endocrine-disrupting potentials. Hence, the monitoring of NAs in aqueous environmental matrices is crucial for oil sands and crude oil production industries. Commonly used analytical methods for NAs include Fourier transform infrared spectroscopy, gas chromatography–mass spectrometry, and high-performance liquid chromatography. However, these methods are time-consuming, expensive, and samples must be sent to an analytical lab for analysis. In this study, we first demonstrated microbial electrochemical cell (MXC)-based biosensor for the rapid detection of a model NA compound (cyclohexane carboxylic acid) in water samples. Under the continuous closed-circuit operation of MXC biosensor, electrical responses (peak currents) were fairly proportional (R2 = 0.64) to the model NA concentrations ranging from 50 to 250 mg COD/L. However, the charging-discharging operation of biosensor significantly increased the peak currents by 90–124 folds higher than that observed for continuous closed-circuit operation. Besides, a linear relationship between model NA concentrations and the peak currents (R2 = 0.96) was observed. Furthermore, it has been revealed that the biosensor would be sensitive to salinity levels and temperature changes; however, once calibrated it can be used for measurement of model NA concentrations. Overall, the results of this study demonstrated that with further development, MXC biosensor could be used as a simple bioanalytical tool for monitoring NA concentrations in oil sands process-affected water.