Application of high-performance liquid chromatography with diode-array detection and on-line post-column photochemical derivatization to the determination of analgesics.

HPLC analyses of pharmaceutical dosage forms containing analgesics and related compounds (acetylsalicyclic acid, paracetamol, propyphenazone, caffeine and chlorpheniramine) were performed on C18 and cyano columns under reversed-phase conditions. The performance of the methods was enhanced by introducing postcolumn on-line photochemical derivatization in combination with a diode-array detection. The column effluents were subjected on-line to UV irradiation (254 nm) and the characteristic photo-induced spectral modifications were useful for the unambiguous identification of the various analgesic compounds. The proposed HPLC methods were successfully applied to the analysis of commercially available analgesic dosage forms.