SPECTROPHOTOMETRIC DETERMINATION OF PHENOLS BY COUPLING WITH DIAZOTIZED 2,4,6-TRIMETHYLANILINE IN A MICELLAR MEDIUM

The unstable absorbances and large values of the blanks obtained when a phenol is determined by Coupling with a diazotized arylamine are caused by hydroxy-de-diazoniation of the diazonium ions, followed by coupling of the resulting phenol with the reagent excess in the basic medium. Diazotized 2,4,6-trimethylaniline (TMA) produces 2,4,6-trimethylphenol, which does not couple with the reagent excess, and gives low blanks. A sodium dodecyl sulfate micellar medium is used to prepare the TMA solutions and to catalyse the coupling reaction. The limits of detection were in the range 0.2-4.6 mu mol dm(-3), with a repeatability of about 2%. The procedure was applied to the determination of epinephrine and paracetamol in pharmaceutical preparations.