1,2-Naphthoquinone-4-sulfonic acid sodium salt as a reagent for spectrophotometric determination of rimantadine and memantine

A selective ultraviolet and visible spectrophotometric method (UV-Vis) for the determination of memantine (MM) and rimantadine (RM) hydrochlorides after derivatization with 1,2-naphtoquinone-4-sulfonic acid sodium salt (NQS) and extraction with dichloromethane was developed and optimized. The reaction of the NQS (0.7%, w/v solution) with memantine was carried out for 40 min in a buffer medium of NaOH/KCl (pH 12.0) at 80°C. A mixture of NQS (0.2%) and rimantadine was heated for 20 min at 50°C, in a medium of NaOH/KCl (pH 12.0). The linearity of the determinations of MM (0.05–0.60 mg/mL) and RM (0.05–0.30 mg/mL) was evaluated. LOD (28 mg/mL for MM, 11 mg/mL for RM) and LOQ (84 mg/mL for MM, 32 mg/mL for RM) values and parameters of precision and accuracy were determined. The UV-Vis method for the determination of rimantadine hydrochloride tablets was validated (selectivity, linearity, precision, accuracy).