Abstract
Titrimetric and spectrophotometric methods are described for the determination of oxcarbazepine (OXC) in bulk drug and in tablets. The methods use N-bromosuccinimide (NBS) and bromopyrogallol red (BPR) as reagents. In titrimetry (method A), an acidified solution of OXC is titrated directly with NBS using methyl orange as indicator. Spectrophotometry (method B) involves the addition of known excess of NBS to an acidified solution of OXC followed by the determination of the unreacted NBS by reacting with BPR and measuring the absorbance of the unreacted dye at 460 nm. Titrimetry allows the determination of 6–18 mg of OXC and follows a reaction stoichiometry of 1 : 1 (OXC : NBS), whereas spectrophotometry is applicable over the concentration range of 0.8–8.0 μg mL−1. Method B with a calculated molar absorptivity of 2.52 × 104 L mol−1 cm−1 is the most sensitive spectrophotometric method ever developed for OXC. The optical characteristics such as limits of detection (LOD), quantification (LOQ), and Sandell's sensitivity values are also reported for the spectrophotometric method. The accuracy and precision of the methods were studied on intraday and interday basis. The methods described could usefully be applied to routine quality control of tablets containing OXC. No interference was observed from common pharmaceutical adjuvants. Statistical comparison of the results with a reference method shows an excellent agreement and indicates no significant difference in accuracy and precision. The reliability of the methods was further ascertained by recovery studies in standard addition procedure.
Highlights
Oxcarbazepine (OXC), is a novel antiepileptic drug, which was developed as a second generation and a follow-up compound to carbamazepine
OXC is not official in any Pharmacopoeia. Various analytical methods such as HPLC [5,6,7,8], HPTLC [9], GC [8], microemulsion electrokinetic chromatography [10], capillary electrokinetic chromatography [11], voltammetry [12, 13] and capillary electrophoresis [14] have been reported for the determination of OXC in pharmaceuticals
Different aliquots (0.4–4.0 mL) of standard 20 μg mL−1 OXC solution were transferred into a series of 10 mL volumetric flasks using a microburette, and the total volume in all the flasks was adjusted to 4 mL by adding 1 : 9 acetic acid
Summary
Oxcarbazepine (OXC), (chemically known as 10,11-dihydro10-oxo-5H-dibenzo[b,f]azepine-5-carboxamide), is a novel antiepileptic drug, which was developed as a second generation and a follow-up compound to carbamazepine. Various analytical methods such as HPLC [5,6,7,8], HPTLC [9], GC [8], microemulsion electrokinetic chromatography [10], capillary electrokinetic chromatography [11], voltammetry [12, 13] and capillary electrophoresis [14] have been reported for the determination of OXC in pharmaceuticals These methods involve the use of expensive instruments which are not available at most quality control laboratories in developing and underdeveloped nations. The method is based on the reduction of iron(III) ions to iron(II) ions by drug, which in presence of hexacyanoferrate(III) produces green coloured chromogen measurable at 770 nm This method is applicable over the concentration range of 4– 28 μg mL−1 OXC with the molar absorptivity value of 4.63 × 103 L mol−1 cm−1. The proposed methods are simple, highly accurate, and can be readily applied to the determination of OXC in bulk drug and in tablets
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