Development of a selective post-column detector for phenols separated by high-performance liquid chromatography

An on-line post-column reactor based on air-segmented continuous flow is described for the determination of phenols. The reaction used is the coupling of diazotized sulfanilic acid with phenols to form highly colored azo dyes. The effect of experimental parameters on the detector response was inveestigated by both univariate and simplex approaches in order to establish optimum reaction conditions. The aqueous reaction system is compatible with common reverse-phase solvents. The detection limit for phneol with the derivatization detector (71 μg 1^?1 shows a 16-fold improvement over u.v. detection of the underivatized phenol. Imprecision, based on multiple injections of sample into the HPLC system and measurement of the peak heights, is ± 0.64% (RSD). The technique is applied to the determination of phenols added to river water and present in residual fuel oil samples.