Identification of hydroquinone and catechol as impurities in reagent‐grade phenol using high performance liquid chromatography with ultraviolet and electrochemical detectors

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Abstract
Several impurities which were suspected to be present in commercial reagent‐grade phenol were separated using high performance liquid chromatography following sample concentration by steam distillation. A reverse‐phase, microparticulate column and 5 solvent systems containing 5% to 25% methanol in 0.05 M phosphoric acid were used. A variable wavelength ultraviolet detector and an electrochemical detector were connected in series, in that order, to the column. Capacity factors (ḱ) for pyrogallol, hydroquinone, resorcinol, catechol, orcinol and phenol were determined in the 5 solvent systems and compared to ḱ‐values of impurities present in the residue remaining from the steam distillation of phenol. Co‐chromatography of standards suspected as contaminants and possessing ḱ‐values similar to those of impurities were carried out in 3 solvent systems to confirm identical retention characteristics. Detector response ratios of contaminants and suspected standards, using various wavelengths and voltage potential settings, were utilized as major identification parameters. Two of the several contaminants separated were identified as hydroquinone and catechol.