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OBJECTIVE: The electrochemical analysis of ephedrine which is a sympathometric drug has been studied using poly(Nile blue A) modified glassy carbon electrodes, cyclic voltammetry, differential pulse voltammetry and square wave voltammetry. METHODS: The modified electrodes were prepared by potential cycling electropolymerization of Nile blue A in 0.1 M phosphate buffer solution at pH 6.0. The redox behavior of ephedrine was investigated in different buffer solutions at pH values between 5.5 and 9.0. RESULTS: Scan rate studies showed that the electron transfer reaction of ephedrine was diffusion controlled. A linear response was obtained between the peak current and the ephedrine concentration in the range of 0.6 to 100 µM with a limit of detection of 2.91×10-3 µM for differential pulse voltammetry in Britton-Robinson buffer solution at pH 9.0. The linearity range of ephedrine in human urine was between 1.0 and 100 µM with a detection limit of 8.16 nM. CONCLUSION: The recovery studies in both pharmaceutical dosage forms and urine showed that the proposed method ensured good selectivity, precision and accuracy without any interference from inactive excipients.

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BACKGROUND: Electroanalytical methods are very functional to detect drugs in pharmaceuticals (tablets, syrups, suppositories, creams, and ointments) and biological samples. OBJECTIVE: This study is aimed to make selective, sensitive, simple, fast, and low cost electrochemical analysis of expectorant drug guaifenesin in pharmaceuticals and serum samples. METHODS: Differential pulse adsorptive stripping voltammetric method for determination of guaifenesin on a poly(acridine orange) modified glassy carbon electrode has been developed. Glassy carbon electrode was modified with electropolymerization of the acridine orange monomer for the sensitive determination of guaifenesin. Guaifenesin provided highly reproducible and welldefined irreversible oxidation peaks at +1.125 V and +1.128 V (vs. Ag/AgCl) in the selected supporting electrolyte and human serum samples, respectively. RESULTS: Under optimized conditions, linear response of peak current on the concentration of guaifenesin has been obtained in the ranges of 2.00×10-7 to 1.00×10-4 M in Britton Robinson buffer solution at pH 7.0 and 4.00×10-7 to 1.00×10-4 M in serum samples. The precision of the method was detected by intraday and inter-day repeatability studies in the supporting electrolyte and serum samples media. CONCLUSION: The analytical applicability of the proposed method exhibited satisfying determination results for guaifenesin from pharmaceutical dosage forms (syrup) and human serum samples without any pre-separation procedures.

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OBJECTIVES: The electro-oxidation behavior of the non-steroidal anti-inflammatory drug tenoxicam (TX) was studied on multiwalled carbon nanotube (MWCNT)-modified glassy carbon electrode (GCE) by cyclic voltammetry, differential pulse voltammetry (DPV), and square wave voltammetry (SWV). MATERIALS AND METHODS: The GCE was modified with MWCNT for sensitive determination of TX by voltammetric methods. RESULTS: The current peaks for TX occurred at around 0.520 V for DPV and 0.570 V for SWV when the potential was scanned in the positive direction. The oxidation process of TX showed irreversible and diffusion-controlled behavior. The linear responses were obtained in the range from 2×10-7 to 1×10-5 M with the limit of detection (LOD) 1.43×10-9 for DPV and from 8×10-9 to 8×10-6 with the LOD 9.97×10-10 for SWV in 1 M acetate buffer solution at pH 5.5. CONCLUSION: Fully validated DPV and SWV were successfully applied for the determination of TX from pharmaceutical dosage form and yielded satisfying results.