Sensitive and cost effective disposable composite electrode based on graphite, nano-smectite and multiwall carbon nanotubes for the simultaneous trace level detection of ascorbic acid and acetylsalicylic acid in pharmaceuticals

In this study, we used nano-smectite (SMT) and multiwall carbon nanotube (MWCNT) as a recognition surface over the disposable pencil graphite electrode for the low-level detection of ascorbic acid (AA) and acetyl salicylic acid (ACA). Firstly, nano-semectit was obtained by the purification of natural bentonite clay. XRD patterns and Scanning electron microscopy (SEM) were employed to ensure the purity of the bentonite samples. Pencil graphite rodes were immersed into suspensions of SMT, MWCNT or the both.The surface morphology of the sensor was investigated by cyclic voltammery (CV), electrochemical impedance spectroscopy (EIS) and SEM techniques. The effect of pH, percentage composition of modifiers, immobilization time, accumulation time and accumulation potential was optimized for reaching the best electroanalytical response for AA and ACA. The sensor developed proved to give good recovery, notable electro-catalytic activity and appropriately distant signals for the simultaneous determination of the analytes. Common contaminates, uric acid, L-cysteine, dopamine, glucose, Na+, Cl- and citric acid were investigated for their interference effects. Uric acid, citric acid and dopamine were found to interfere to some extent. The electrode exhibited wide working ranges and a fairly satisfactory detection limit of 0.096 and 0.241 mu M for AA and ACA, respectively. The electrode system proved to be practical for the analysis of pharmaceutical tablets and the recovery results are very satisfactory.