Multiwall carbon nanotube modified glassy carbon electrode as voltammetric sensor for the simultaneous determination of ascorbic acid and caffeine

Simultaneous determination of ascorbic acid (AA) and caffeine (CAF) in pharmaceutical preparation is important and it has been achieved by square wave voltammetry (SWV) using a glassy carbon electrode (GCE) modified with multiwall carbon nanotubes (MWCNT). The oxidation of AA and CAF at MWCNT occurred at ∼−10mV and ∼1103mV at a much lower potential, than that observed (∼202mV and ∼1402mV) for their oxidation at bare GCE. The mechanistic study has shown that the equal number of electrons and protons are involved in the oxidation of drugs. The electrodes could be used for the determination of AA and CAF in a wide concentration range 10–500μM, respectively, whereas the detection limit has been found to be 1.0×10−2μM and 3.52×10−3μM respectively. In view of high sensitivity for the detection of the drugs, the technique has been used for the reliable determination of AA and CAF in tea leaves, coffee, cold drink (mountain dew), pharmaceutical preparations and urine samples.