Simple, rapid, accurate and sensitive spectrophotometric methods are described for the determination of norfloxacin. The methods are based on the reaction of this drug as a π-electron donor with 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ), 7,7,8,8-tetracyanoquinodimethane (TCNQ), p-chloranil (CL) or chloranilic acid (CLA) as π-acceptors to give highly coloured complex species. The coloured products are measured spectrophotometrically at 460, 843, 550 and 531 nm for DDQ, TCNQ, CL and CLA, respectively. Optimization of the different experimental conditions is described. Beer's law is obeyed in the range 10–400 µg ml–1 and colours were produced in non-aqueous media and were stable for at least 3 h. Applications of the suggested methods to representative pharmaceutical dosage forms are presented and compared with the official method. Interferences from additives and common degradation products were investigated. |
