Application of spectrophotometric, densitometric, and HPLC techniques as stability indicating methods for determination of Zaleplon in pharmaceutical preparations

Spectrophotometric, spectrodensitometric and HPLC are stability indicating methods described for determination of Zaleplon in pure and dosage forms. As Zaleplon is easily degradable, the proposed techniques in this manuscript are adopted for its determination in presence of its alkaline degradation product, namely N-[4-(3-cyano-pyrazolo[1,5a]pyridin-7-yl)-phenyl]-N-ethyl-acetamide. These approaches are successfully applied to quantify Zaleplon using the information included in the absorption spectra of appropriate solutions. The second derivative (D-2) spectrophotometric method, allows determination of Zaleplon without interference of its degradate at 235.2 ran using 0.01N HCI as a solvent with obedience to Beer's law over a concentration range of 1-10 mu g ml(-1) with mean percentage recovery 100.24 +/- 0.86%. The first derivative of the ratio spectra ((DD)-D-1) based on the simultaneous use of ((DD)-D-1) and measurement at 241.8 nm using the same solvent and over the same concentration range as (D-2) spectrophotometric method, with mean percentage recovery 99.9 +/- 1.07%. The spectrodensitometric analysis allows the separation and quantitation of Zaleplon from its degradate on silica gel plates using chloroform: acetone: ammonia solution (9:1:0.2 by volume) as a mobile phase. This method depends on quantitave densitometric evaluation of thin layer chromatogram of Zaleplon at 338 ran over a concentration range of 0.2-1 mu g band(-1), with mean percentage recovery 99.73 +/- 1.35. Also a reversed-phase liquid chromatographic method using 5-C8 (22 cm x 4.6 mm i.d. 5 mu m particle size) column was described and validated for quantitation of Zaleplon using acetonitrile deionised water (35:65, v/v) as a mobile phase using Paracetamol as internal standard and a flow rate of 1.5 ml min(-1) with UV detection of the effluent at 232 run at ambient temperature over a concentration range of 2-20 mu g ml(-1) with mean percentage recovery 100. 19 +/- 1.15 %. The insignificance difference of the proposed methods results with those of the reference one proved their accuracy and precision. (c) 2007 Elsevier B.V. All rights reserved.