Electrochemical Study of Zolpidem at Glassy Carbon Electrode and Its Determination in a Tablet Dosage Form by Differential Pulse Voltammetry

Abstract

Zolpidem ( Fig. 1), (N,N,6-trimethyl-2-(4-methylphenyl)-imidazole[1,2-a]pyridine-3-acetamide, is a non-benzodiazepine hypnotic drug with an imidazopyridine backbone, which acts in the brain principally at receptors of the w 1 -receptor subtype belonging to the g-aminobutyric acid-(GABA)ergic system. 1) Zolpidem is characterized by its fast onset of action and relatively short elimination half-life ranging between 1.4 and 4.5 h.2) For this reason bedtime administration carries a low risk of residual daytime sedative effects. 3,4) Many analytical methods have been published for the determination of zolpidem based on high-performance liquid chromatography (HPLC) combined with ultraviolet, 5) fluorescence 6,7) and with photodiode-array detection, 8) gas chromatography-nitrogen phosphorus detection, 9) gas chromatography-mass spectrometry, 10,11) capillary electrophoresis with laser-induced fluorescence detection 12) and radioimmunoassay. 13)However, to our knowledge no information about the electrochemical redox properties of zolpidem and its analytical application has appeared in the literature. The present study deals with the voltammetric oxidation behaviour of zolpidem on glassy carbon electrode and its determination by differential pulse voltammetry (DPV) in a tablet dosage form. ExperimentalReagents Zolpidem hemitartrate was kindly supplied by Amriya for Pharmaceutical Industries (Alexandria, Egypt) and was used without prior purification. Stilnox ® tablets were purchased from local pharmacies. Each tablet was labeled to contain 10 mg zolpidem hemitartrate. Methanol (Merck) was of HPLC grade; water was doubly distilled. All other chemicals were of analytical-reagent grade (Merck or Sigma) and were used as received.Zolpidem stock solutions were prepared daily by direct dissolution in methanol. Britton-Robinson buffers (0.04 M of each of acetic, o-phosphoric, and boric acids, adjusted to the required pH with 0.2 M sodium hydroxide solution) were used as supporting electrolytes.Apparatus The voltammetric measurements were performed using a PC controlled AEW2 analytical electrochemical workstation with ECprog3 electrochemistry software (Sycopel, U.K.) connected to C-2 stand with a three-electrode configuration: a glassy carbon (Fϭ3 mm) working electrode, an Ag/AgCl/3 M KCl reference electrode and a platinum wire counter electrode. OriginPro 7.0 software was used for the transformation of the initial signal. A CG 808 (Schott Geräte, Germany) digital pH meter with glass combination electrode served to carry out the pH measurements.Procedure. Recommended Procedure Ten milliliters of the electrolyte solution were transferred into the voltammetric cell. After measurement of the blank solution, the appropriate amount of zolpidem solution is added and the anodic potential sweep was carried under different operational parameters. All measurements were carried out at room temperature, and peak heights were evaluated by means of the tangent method. The electrode must be rinsed with methanol and deionized water prior to each...

Electrooxidation of Zolpidem and its Voltammetric Quantification in Standard and Pharmaceutical Formulation using Pencil Graphite Electrode

“…In comparison with the lone research that worked on the electrochemical behavior of ZP, the PG electrode in the presence of ZP has almost similar potential peak with glassy carbon electrode [23]. Further, its sensitivity is approximately 50 times higher than that of the glassy carbon electrode [23].…”

“…A useful electrode geometry for analytical purposes is a cylinder rather than a disk, partly because the use of a longer cylinder electrode enhances sensitivity as surface poisoning do not occur [32]. In comparison with the lone research that worked on the electrochemical behavior of ZP, the PG electrode in the presence of ZP has almost similar potential peak with glassy carbon electrode [23]. Further, its sensitivity is approximately 50 times higher than that of the glassy carbon electrode [23].…”

“…At the best of our knowledge, only one report has described an electrochemical method for determining ZP concentrations using a glassy carbon electrode [23]. Although disposable pencil graphite (PG) electrode is relatively new type of carbon electrode, it has been successfully applied to the cathodic and anodic voltammetry by virtue of its high electrochemical reactivity, commercial availability, good mechanical rigidity, low cost, low technology and ease of modification [24][25][26].…”

Chemiluminescence System of Permanganate-Sulfite for Simple Determination of Zolpidem

“…Various analytical methods have been proposed for the determination of zolpidem such as liquid chromatography with mass spectrometry detection [5][6][7][8][9][10][11], high performance liquid chromatography with spectrophotometric detectors [12][13][14], capillary electrophoresis [15], gas chromatography [16][17], spectrophotometry [18,19], potentiometry [20], voltammetry [21] and Radioimmunoassay [22].…”

Development and validation of a stability-indicating reversed phase HPLC method for the quality control of Zolpidem in bulk and tablet dosage forms

“…There are a few published analyt ical methods used for determination of Zolpidem in bulk and pharmaceutical dosage forms such as HPTLC [22], differential pulse voltammetry [23], simple spectrophotometry [24] and HPLC [25,26]. In order to apply of an analytical method for quality con trol analysis in pharmaceutical industries, it is pre ferred that any analytical method should be stability indicating [27][28][29][30].…”