Abstract
Diclofenac (DCF) is a non-steroidal anti-inflammatory drug used for the treatment of different diseases such as rheumatoid arthritis, spondylitis, arthritis and sport injuries. Increased use of DCF has initiated a significant worry regarding their presence in the environment. This study reports a sensitive and selective electrochemical sensing platform based on poly glycine modified carbon nanotube paste electrode (PGMCNTPE) for the simultaneous determination of DCF and dopamine (DA) by differential pulse voltammetry (DPV). The characterisation techniques like cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) accomplished in 1 mM K-4 [Fe (CN)(6)], displays that the electroactive surface area of PGMCNTPE is augmented and the charge-transfer resistance is diminished in comparison to the bare carbon nanotube paste electrode (BCNTPE). Various parameters responsible for the peak improvement such as accumulation time, accumulation potential, pH and number of polymerisation cycles were optimised. Scan rate studies done by CV technique reveals that the process is irreversible and adsorption controlled in 0.2 M solution of phosphate buffer (PBS). The deposition of the poly glycine film on the BCNTPE surface enhanced the sensors electronic transfer rate, which reveals a heterogeneous rate constant (k(0)) of 3.13 x 10(-3) s(-1). PGMCNTPE shows two linear ranges with an increase in DCF concentration from 4 to 100 mu M and a detection limit calculated by considering second linear range was found to be 0.21 mu M. The selectivity of PGMCNTPE towards DCF was investigated in the existence of various interfering molecules and inorganic metal ions with fivefold higher concentration. The pertinence of the proposed sensor was analysed by quantification of DCF in pharmaceutical samples. The prepared sensor exhibits a virtuous performance in detection of DCF due to excellent repeatability, reproducibility and stability.