Analysis of phenols in pharmaceuticals by liquid chromatography after pre-column labelling and on-line post-column photochemical derivatization Original Research Article

Reversed phase high-performance liquid chromatographic (RP-HPLC) methods are proposed for the analysis of phenol, thymol, chlorocresol and chloroxylenol in commercial pharmaceutical dosage forms. The use of 1-fluoro-2,4-dinitrobenzene as UV labelling reagent in pre-column derivatization has been investigated. The compound reacts rapidly (2 min) under mild conditions (ambient temperature or 40°C) with phenols to give ethers that can be separated by RP-HPLC and detected at 292 nm. The other procedure involves a post-column on-line photochemical conversion. A photoreactor was arranged between the analytical column and the fluorescence (λex=270 nm, λem=310 nm) and UV-diode array (λ=270 nm) detector to enhance the performance of the methods. Additional informations of the analyte structure and photoreactivity by UV spectra (photoreactor ‘on’ and ‘off’) were obtained. The methods showed good selectivity and sensitivity.