Chemometrically Assisted Development and Validation of LC for Simultaneous Determination of Carbamazepine and Its Impurities Iminostilbene and Iminodibenzyl in Solid Dosage Form

Appraisal of the greenness profile of a chromatographic method for the simultaneous estimation of carbamazepine and oxcarbazepine, along with two potential impurities and three formulation excipients

Structurally related carbamazepine (CBZ) and oxcarbazepine (OX) are two of the most commonly used antipsychotic drugs. The main impurities of CBZ, as described in both the USP and the BP, are iminodibenzyl (IMD) and iminostilbene (IST). Meanwhile, for non-pharmacopeial OX, the declared impurities include CBZ and IST. Prescribed oral suspensions of CBZ and OX contain additives including methyl paraben (MP), propyl paraben (PP) and sorbic acid (SA) as preservatives. An HPTLC method was introduced and developed for resolving the interference between CBZ, OX, their impurities, and the suspension additives in a single run, in addition to their quantitation with a high sensitivity that satisfies the USP requirements for the detection and quantitation of drug impurities. In the developed HPTLC method, CBZ and OX were measured in the range of 40–4000 ng per band, while IMD, IST, MP, PP and SA were in the range of 20–2000 ng per band, using a mixture of hexane : ethylacetate : formic acid : acetic acid (8 : 2 : 0.5 : 0.3, by volume) and UV scanning at 254 nm. The greenness profile of the method was evaluated by two different tools, the analytical Eco-Scale and the Green Analytical Procedure Index (GAPI), then a comparison between their results was conducted. This is the first time that the studied drugs, along with their impurities and suspension additives, were analyzed by a HPTLC method in a single run and within the limits required by the USP guidelines.

Structurally related carbamazepine (CBZ) and oxcarbazepine (OX) are two of the most commonly used antipsychotic drugs.

Spectrophotometric Determination of Carbamazepine in Pharmaceutical Formulations Based on its Reaction with a Brominating Agent

Two accurate spectrophotometric methods described for the estimation of carbamazepine (CBZ) in both pharmaceutical and pure form. These methodologies are attached to the bromination of CBZ by bromine formed in instantly from the bromate-bromide reaction. The general procedure includes the additional of a known amount of bromate-bromide reagent in an acidic mediocre to CBZ. After the reaction is integrated, the unreacted bromine was reacted with a steady amount of methylene blue, and the absorbance was measured at 665 nm (method A) or, cresol red could be used for the reaction and the absorbance moderated at 517 nm (method B). Beer’s law was submitted from 0.45 to 15.00 μg/mL CBZ with a molar absorptivity of 4.93 × 103 L/mol.cm for method A and from 0.50 to 12.00 μg/mL CBZ with a molar absorptivity of 1.37 × 104 L/mol.cm for method B. The proposed methods were effective for the determination of CBZ in tablets with great precision and accuracy.

Stability indicating spectrophotometric methods for quantitative determination of carbamazepine and its degradation product, iminostilbene, in pure form and pharmaceutical formulations

A stressed study on the stability and degradation behavior under ICH forced degradation conditions of most widely used antiepileptic drug; carbamazepine (CMZ) is presented in this work. The research also includes studying spectrophotometric nature of CMZ and assaying it with mostly used spectrophotometric techniques. Six simple and sensitive spectrophotometric methods are introduced as stability indicating methods for quantitative determination of CMZ and its degradation product, one of its reported potential impurities; iminostilbene (IMS). Dual wavelength is method I where two wavelengths (215 and 270 nm for CMZ and 258 and 307 nm for IMS) were chosen for each component while absorbance difference is zero for the second one. Method II is isoabsorptive point method where the absorbance of CMZ at A_{225 nm} was measured in the range of 0.5-20 μg mL^-1. Method III is second derivative method which allows simultaneous determination of CMZ at 247 nm and IMS at 273 nm without any interference. Method IV based on measuring the peak amplitude of first derivative of ratio spectra (¹DD) at 280.5 and 253 nm for determination of CMZ and IMS, respectively. Method V is mean centering of the ratio spectra with good linearity for CMZ and IMS over 200-330 nm. Ratio difference method is method VI where good linearity was achieved for determination of CMZ and IMS by measuring differences in the amplitude of ratio spectra at 285, 258 nm and 258, 285 nm, respectively. The proposed methods show successful application in CMZ's pharmaceutical formulations.