Preparation of Carbon-Ceramic Electrode Modified with Multiwalled Carbon Nanotubes (MWCNTs) and its Application in Simultaneous Determination of Mefenamic Acid and Acetaminophen in Pharmaceutical Preparations and Biological Samples

Drug analysis is essential in various stages of drug design and development, such as formulation, quality control stability studies, pharmacokinetics and pharmacodynamics, pre clinical and clinical trials. Mefenamic acid (MEF, 2-[(2,3-dimethylphenyl) amino] benzoicacid) is a nonsteroidal anti-inflammatory drug with anti-inflammatory, analgesic and antipyretic properties. It is extensively used in the treatment of many diseases like rheumatoidarthritis, osteoarthrits, nonarticular rheumatism and sport injuries. Acetaminophen(paracetamol) (N-acetyl-paminophenol) is a popular, antipyretic and non-steroidal anti-inflammatory drug. Combinations of MEF and ACT are frequently prescribed for analgesic and anti-inflammatory use in rheumatoid arthritis. Accordingly determination of the levels of these present in pharmaceuticals is of considerable importance, to prevent overdoses leading to toxic effects. Electrochemical analysis offers a number of important advantages over traditional chemical analyses for providing information on drug analysis and its metabolic fate in vivo, redox processes and pharmacological activity. So, the carbon-ceramic electrode was modified by multiwalled carbon nanotubes (MWCNTs) by drop casting of suspension of carbon nanotubes in dimethylformamide (DMF). The surface morphology and interfacial properties of the modified electrode was characterized by scanning electron microscopy (SEM) and electrochemical impedance spectroscopy techniques, respectively. This modified electrode was applied for electrochemical behavior study and simultaneous determination of acetaminophen and mefenamic acid. Cyclic voltammetry experiments showed two well defined, resolved and sensitive peaks for acetaminophen and mefenamic acid compared with bare electrode. So, the 233 experimental parameters which affect the analytical performance of modified electrode towards acetaminophen and Mefenamic acid were optimized. After that the calibration graphs were constructed for analytes by simultaneous increasing of them concentration in the range of 0.08-3 μM and 0.1-3.5 μM with the detection limit of 0.073 μM and 0.09 μM by differential pulse voltammetry for acetaminophen and Mefenamic acid, respectively. Lastly, the modified electrode was used for simultaneous determination of acetaminophen and mefenamic acid in some pharmaceutical and urine samples with satisfactory discovery percents.