Spectrofluorimetric determination of paroxetine HCl in pharmaceuticals via derivatization with 4-chloro-7- nitrobenzo-2-oxa-1,3-diazole (NBD-Cl).

A sensitive and simple spectrofluorimetric method has been developed and validated for the determination of the antidepressant paroxetine HCl (PXT) in its dosage forms. The method was based on coupling reaction of PXT with 4-chloro-7-nitrobenzo-2- oxa-1,3-diazole (NBD-Cl) in an alkaline medium (pH 8) to form a highly fluorescent derivative that was measured at 530 nm after excitation at 460 nm. The factors affecting the formation and stability of the reaction product were carefully studied and optimized. The fluorescence-concentration plot is rectilinear over the range 0.2-6 μg/mL with LOD of 0.08 μg/mL and LOQ of 0.24 μg/mL respectively. The method was applied to the analysis of commercial tablets and the results were in good agreement with those obtained using the reference method. The mean percentage recoveries for paxetin and xandol tablets were 101.27 ± 1.79 and 101.33 ± 1.19 respectively. A proposal of the reaction pathway was postulated.