A highly improved method for sensitive determination of amitriptyline in pharmaceutical formulations using an unmodified carbon nanotube electrode in the presence of sulfuric acid

• Published in: Talanta (Oxford) 2014-09, Vol.127, p.26-32
• Main Authors: Henrique Duarte, Eduardo, dos Santos, William Pereira, Fantinato Hudari, Felipe, Bott Neto, José Luiz, Romão Sartori, Elen, Dall׳Antonia, Luiz Henrique, César Pereira, Arnaldo, Teixeira Tarley, César Ricardo
• Format: Article
• Language: English
• Subjects: Adsorption; Amitriptyline - analysis; Amitriptyline - chemistry; Brazil; Carbon; Carbon nanotube paste electrode; Carbon nanotubes; Differential pulse voltammetry; Electrochemical Techniques; Electrodes; Excipients - chemistry; Formulations; Nanotubes, Carbon - chemistry; Oxidation-Reduction; Pharmaceutical Preparations - chemistry; Pharmaceuticals; Silver; Sulfuric acid; Sulfuric acid medium; Sulfuric Acids - chemistry; Tricyclic antidepressants
• ISSN: 0039-9140; 1873-3573
• DOI: 10.1016/j.talanta.2014.03.068

The present paper describes a novel, simple and reliable differential pulse voltammetric method for determining amitriptyline (AMT) in pharmaceutical formulations. It has been described for many authors that this antidepressant is electrochemically inactive at carbon electrodes. However, the procedure proposed herein consisted in electrochemically oxidizing AMT at an unmodified carbon nanotube paste electrode in the presence of 0.1molL−1 sulfuric acid used as electrolyte. At such concentration, the acid facilitated the AMT electroxidation through one-electron transfer at 1.33V vs. Ag/AgCl, as observed by the augmentation of peak current. Concerning optimized conditions (modulation time 5ms, scan rate 90mVs−1, and pulse amplitude 120mV) a linear calibration curve was constructed in the range of 0.0–30.0μmolL−1, with a correlation coefficient of 0.9991 and a limit of detection of 1.61μmolL−1. The procedure was successfully validated for intra- and inter-day precision and accuracy. Moreover, its feasibility was assessed through analysis of commercial pharmaceutical formulations and it has been compared to the UV–vis spectrophotometric method used as standard analytical technique recommended by the Brazilian Pharmacopoeia. [Display omitted] •Unmodified carbon nanotubes electrode was used for AMT determination.•Electrode surface regeneration or renewal is not required.•Reliable precision was observed.•The method provides satisfactory limit of detection.