RESUMO
An electrochemical sensor for the sensitive detection of valacyclovir has been developed, which is based on single-walled carbon nanotube (SWCNT)-modified glassy carbon electrodes. The electrochemical oxidation of valacyclovir at the SWCNT-modified glassy carbon electrodes has been investigated using cyclic voltammetry and differential pulse voltammetry. Our experimental results show that the SWCNT-modified glassy carbon electrode possesses high activity toward the electrochemical oxidation of valacyclovir. In a 0.1 M phosphate buffer (pH = 7.4), valacyclovir exhibited an irreversible oxidation peak at -0.91 V. The effects of pH of and the amount of SWCNT deposited on the glassy carbon electrode on the activity of the sensor have also been studied. Under optimized conditions, the sensor demonstrates a linear response range from 5 x 10(-9) to 5.5 x 10(-8) M valacyclovir. The detection and quantification limits were found to be 1.80 x 10(-9) M and 6.02 x 10(-9) M, respectively. The selectivity, stability and reproducibility of the proposed sensor were examined as well. To validate its real world application, the electrochemical sensor has been successfully utilized in the detection of valacyclovir in human blood plasma and pharmaceutical samples. Thus, the electrochemical sensor developed in this study has strong potential to be employed in the quality control testing of pharmaceutical products and also for therapeutic drug monitoring in hospitals.
