Abstract
This work describes the development and validation of five fast, simple, accurate and precise spectrophotometric methods for the determination of loxoprofen sodium (LXP) through charge transfer complexation reactions. The first method is based on the development of a purple colored product with maximum absorbance at 523 nm after reaction of LXP with p-chloranilic acid (p-CA) in acetone. The second method depends on the formation of a bluish-green product measured at 844 nm through the reaction of LXP with 7,7,8,8-tetracyanoquinodimethane (TCNQ) in acetone. The third method involves the formation of a yellow chromogen with a strong absorption maximum at 458 nm upon the reaction of LXP with 2,3-dichloro5,6- dicyano-p-benzoquinone (DDQ) in acetonitrile. The fourth method is based upon the production of a yellow complex measured at 414 nm the interaction of LXP and picric acid (PA) in chloroform. The fifth method yields a yellow complex with maximum absorption at 361 nm upon the interaction of LXP with iodine in chloroform. Optimization of experimental conditions that affect the color development was accomplished. Stoichiometry of the reactions was studied. Validation of the proposed spectrophotometric methods was made in terms of linearity, ranges, precision, accuracy, robustness, detection and quantification limits. The formed color products of LXP with p-CA, TCNQ, DDQ, PA and iodine showed good linear relationships over the concentration ranges 40-240, 1-10, 16-96, 8-32 and 2-12 mu g/mL respectively. The proposed methods were suitably employed for the assay of LXP in bulk drug and pharmaceutical dosage forms. No spectral interferences from the tablet excipients were found.