Flow-injection spectrophotometric determination of paracetamol in tablets and oral solutions.

A flow injection method is proposed for the determination of paracetamol in pharmaceutical dosage forms. The method is based on the nitration of paracetamol with sodium nitrite, and the absorption of the reaction product is measured at 430 nm in alkaline medium. Unlike other colorimetric methods used for determination of paracetamol, this method does not require the use of heat. The influence of several operating parameters is studied. The method was applied to the determination of paracetamol in oral solutions and in tablets, alone or associated with caffeine. When the results were compared with those obtained by the official HPLC method (USP 24) the relative differences found were from 0.4 to 2.3%, with relative standard deviations below 1%.