Derivative spectrophotometric analysis of benzophenone (as an impurity) in phenytoin.

Three simple and rapid spectrophotometric methods were developed for detection and trace determination of benzophenone (the main impurity) in phenytoin bulk powder and pharmaceutical formulations. The first method, zero-crossing first derivative spectrophotometry, depends on measuring the first derivative trough values at 257.6 nm for benzophenone.

Spectrofluorimetric determination of ciclopirox olamine via ternary complex with Tb(III) and EDTA.

A highly sensitive and selective spectrofluorimetric method was developed for the determination of ciclopirox olamine in raw material and in dosage forms. The proposed method is based on the formation of a ternary complex with Tb(III) in the presence of ethylenediaminetetraacetic acid. It was found that this complex manifests intense fluorescence at lambda(em) 489 and 545 nm with excitation at 295 nm.