The use of optical and atomic force microscopy for probing the sensing mechanism of hazardous tellurium species for environmental applications

Abstract

Determination of tellurium compounds is of particular interest because of the intrinsic toxicity associated with its water-soluble oxyanions, tellurite TeO32−. Among various analytical approaches, carbon paste sensors (CPSs) are widely used for the determination of heavy metals, nucleic acids and other organic compounds due to their simplicity, sensitivity and cost-effectiveness. In this study, chemically modified carbon paste sensor is developed for the analysis of tellurite ions in pure and in real samples. The sensor showed nearly Nernstian behavior (30 mV) with wide linear range and low detection limit. Moreover, the sensor was successfully applied to the determination of tellurite in environmental and biological samples such as wastewater, human serum, tellurite culture media, synthetic tellurite-cefotaxime and tellurite/tellurate mixtures. The results show high recovery rates, selective and highly reproducible response, indicating the suitability of the proposed sensor for practical applications. In addition, we studied how several parameters such as the type of carbon, type of the plasticizer, amount of the modifier and composition of the sensor affect its electrochemical performance. This was achieved by tracing the morphology and composition of the electrode using optical and atomic force microscopy. The combination of these techniques provides valuable information on the physical, mechanical and chemical properties of the sensor, which proved to be very helpful in understanding its behavior under different chemical conditions. The study also gives some insights on the optimization of chemical sensors based on chemically modified carbon paste sensors.