Carbon Nanotube Electrodes in Comparison to Coated Platinum Wire and Carbon Paste Selective Electrodes for the Determination of Tramadol Hydrochloride in Bulk, Pharmaceutical Formulations, and Spiked Human Plasma and Urine

Abstract

Potentiometric selective electrodes are designed for the electrochemical determination of tramadol hydrochloride (TR.HCl). They are synthesized using coated platinum wire, a carbon paste electrode, and multiwall-carbon-nanotube (MWCNT)-modified carbon paste electrodes. The membranes of the studied electrodes use different types of ionophores as a key element in TR.HCl detection, such as 18-crown-6-ether, β cyclodextrin, and calix[4]arene neutral ionophores. The matrix composition of each electrode is optimized according to ionophore type and concentration, concentration and type of the plasticizer used, and percent of MWCNT added to the carbon paste electrodes. The developed electrodes are completely characterized according to the working concentration range, response time, and suitable pH and temperature range. The developed sensors exhibit excellent stability (more than 8 weeks) with fast dynamic response (<5 s) especially because of the incorporation of MWCNTs which improves the characteristics of the electrodes. The proposed electrodes showed excellent selectivity to TR.HCl in the presence of other related substances. The sensors were applied successfully for the quantitation of TR.HCl in pure form, pharmaceutical dosage form, and in spiked human plasma and urine. They are also applied for quantitation of TR.HCl in dissolution testing of the tablet dosage form.