Simultaneous determination of benzocaine and cetylpiridinium chloride in tablets by first-derivative spectrophotometric method.

A new spectrophotometric method for the simultaneous determination of benzocaine and cetylpiridinium chloride in pharmaceutical tablets, which does not require any preliminary separation or treatment of the samples, is described. The quantitative determination of both drugs was carried out using the first derivative values measured at 231.40 and 310.00 nm for benzocaine and at 220.70 nm for cetylpiridinium chloride using the zero-crossing method. The calibration graphs were linear in the ranges from 10 to 25 mg/l of benzocaine and from 4 to 20 mg/l of cetylpiridinium chloride. The developed method was successfully applied for the assay of pharmaceutical tablets and proved to be simple, sensitive and selective. Thermogravimetric techniques, Karl Fischer and loss on drying were also used for a stoichiometric evaluation of the substances studied.