Cathodic Stripping Voltammetric Determination of Doxazosin in Urine and Pharmaceutical Tablets Using Carbon Paste Electrodes

Abstract

Several voltammetric techniques were used to explore the reductive behaviour of the antihypertensive agent doxazosin on a bare carbon paste (CPE) and a Tenax-modified carbon paste electrode (TMCPE). The results indicate that the process is irreversible and fundamentally controlled by adsorption, which allows doxazosin to be accumulated at the electrode surface. The cathodic adsorptive stripping (AdS) response was evaluated with respect to pH, accumulation variables and instrumental parameters, using differential-pulse (DPV) and square-wave voltammetry (SWV) as redissolution techniques. In both cases, a voltammetric peak close to 0 V in Britton-Robinson buffer (pH 6.6) was obtained after a preconcentration step at 0.55 V for 3 min (2000 rpm) and a subsequent cathodic scan. When the TMCPE was used, the limits of detection were 4.35 x 10(-11) and 5.18 x 10(-11) M for AdS-DPV and AdS-SWV, respectively. The deposition time (3 min) was improved relative to that obtained by means of CPE (6 min). Under the optimum operational conditions, the doxazosin reduction peak showed a linear response in the range from 6 x 10(-11) to 1 x 10(-9) M by using AdS-DPV, with an RSD of 3.39% for 3 x 10(-8) M doxazosin solution (n = 10). A method was developed for the determination of doxazosin in human urine and formulations.

Electrochemical Behavior and Determination of Ketoconazole from Pharmaceutical Preparations

“…As is obvious, the second oxidation process is chemically irreversible. A similar irreversible behavior was reported for the electrooxidation of the piperazine rings of trazodone and doxazosin drug molecules [23,24].…”

“…The cathodic peak is formed as a consequence of the reduction of the ®rst oxidation product of KC. The piperazine ring of the KC molecule is oxidized at high positive potentials (close to the solvent evolution) in a similar process to that reported for the oxidation of the piperazine rings of trazodone [23] and doxazosin molecules [24]. The anodic peak at 870 mV is due to the oxidation of the cathodic peak.…”

“…cation radical is the loss of an electron from the piperazine ring of the KC molecule [23,24]. However, the initial reversible oxidation step may occur as a result of the loss of an electron from either the imidazole ring or the methoxyl group of the drug molecule.…”

Determination of doxazosin and verapamil in human serum by fast LC–MS/MS: Application to document non-compliance of patients

“…Determination of doxazosin in pharmaceutical formulations and biological matrices was performed using HPLC-UV [33], HPLC-FLR [34][35][36][37][38][39][40] and LC-MS [41][42][43]. Doxazosin was also analysed using electrochemical techniques [44,45]. A method for simultaneous determination of both analytes was not published so far.…”

Validated specific HPLC methods for determination of prazosin, terazosin and doxazosin in the presence of degradation products formed under ICH-recommended stress conditions

“…Methods involving pulse polarography [39][40][41], voltammetry [42][43][44][45], HPTLC [46], spectrophotometry [44] and flow injection analysis using UV-detection [47] have been reported for the determination of this drug in pharmaceutical preparations. Voltammetric [42][43][44], spectrophotometric [44], and liquid chromatographic [48,49] methods have been employed for the analysis of doxazosin in biological samples.…”