Electrooxidation of Indomethacin at Multiwalled Carbon Nanotubes-Modified GCE and Its Determination in Pharmaceutical Dosage Form and Human Biological Fluids

A simple, rapid, selective, and sensitive electrochemical method for the direct determination of indomethacin was developed. The electrochemical behavior of indomethacin was carried at multiwalled carbon nanotube- (MWCNTs-) modified glassy carbon electrode (GCE). The cyclic voltammetric results indicated that MWCNT-modified glassy carbon electrode remarkably enhanced electrocatalytic activity towards the oxidation of indomethacin in slightly acidic solutions. It led to a considerable improvement of the anodic peak current for indomethacin and could effectively accumulate at this electrode and produce two anodic peaks at 0.720？V and 0.991？V, respectively, and one reduction peak at 0.183？V. The electrocatalytic behavior was further exploited as a sensitive detection scheme for the determination of indomethacin by differential-pulse voltammetry (DPV). Under optimized conditions, the concentration range and detection limit were 0.2 to 6.0？ M and 13.2？nM, respectively. The proposed method was successfully applied to determination of Indomethacine in pharmaceutical samples. The analytical performance of this sensor has been evaluated for detection of analyte in human serum and urine as real samples. 1. Introduction Indomethacin, (Scheme 1) {1-(p-chlorobenzoyl)-5-methoxy-2-methyl-3-indolylacetic acid} (INM), a nonsteroidal anti-inflammatory drug, is usually regarded as the father figure in the family of nonsteroidal agents. It relieves pain and reduces inflammation and fever. It is slightly more toxic but in certain circumstances more effective than aspirin. INM has two additional modes of actions [1] with clinical importance. It inhibits motility of polymorphonuclear leukocytes and, like salicylates, uncouples oxidative phosphorylation in cartilaginous (and hepatic) mitochondria. These additional effects account as well for the analgesic and the anti-inflammatory properties. Generally, overdose in humans causes drowsiness, dizziness, severe headache, mental confusion, numbness of limbs, nausea and vomiting, severe gastrointestinal bleeding, and cerebral edema and cardiac arrest, its fatal outcome is seen in children. For these reasons, it is important to analyze INM in real samples. Scheme 1: Chemical structure of indomethacin. The widespread use of INM and the need for clinical and pharmacological study require fast and sensitive analytical techniques to determine the presence of INM in pharmaceutical formulations and biological fluids. Until now, the most common techniques for the determination of INM in commercial dosage form were based on