Optimized and validated spectrophotometric methods for the determination of levocetirizine in pharmaceuticals based on charge transfer reaction

Three rapid, selective and sensitive spectrophotometric methods have been proposed for the quantitative determination of levocetirizine dihydrochloride (LCT) in pure form as well as in its pharmaceutical formulation. The methods are based on the charge transfer complexation reaction of LCT as n-electron donor with 2,4-dinitrophenol (DNP), picric acid (PA) as π-acceptors and iodine (I2) as σ-acceptor to give highly colored radical anion species. The colored products were quantified spectrophotometrically at 420 nm with both DNP (method A) and PA (method B) and at 375 nm with I2 (method C). Under the optimized experimental conditions, Beer’s law is obeyed over the concentration ranges of 1.2–24, 1.6–32 and 2.4–48 μg mL−1 LCZ for method A, method B and method C, respectively. The values of molar absorptivity, Sandell sensitivity, limits of detection and quantification are also reported. The effect of reaction medium, reaction time and reagent concentration on the sensitivity and stability of the complexes formed has been examined. The proposed methods were successfully applied to the determination of LCT in pure form and commercial tablets and in syrup with good accuracy and precision. Statistical comparison of the results was performed using Student’s t-test and F-ratio at 95% confidence level and the results showed no significant difference between the reference and proposed methods with regard to accuracy and precision. Further to the accuracy and reliability the methods were confirmed by recovery studies via the standard addition technique.