Determination of phenols with ion chromatography–online electrochemical derivatization based on porous electrode–fluorescence detection

The current study describes the determination of phenols using ion chromatography–online electrochemical derivatization–fluorescence detection (IC/ED/FD). Six model phenols including 4-methylphenol (pMP), 2, 4-dimethylphenol (DMP), 4-tert-butylphenol (TBP), 4-hydroxylphenolacetic acid (pHPA), 4-acetamidophenol (pAAP), and phenol (P) were well separated on an anion-exchange column under ion exchange mode using NaOH with small amount of acetonitrile added as eluent. Online electrochemical derivatization performed via a laboratory-made electrolytic cell (EC), consisting of porous titanium electrode and cation-exchange membrane (CEM), allows the oxidation products that are strongly fluorescent to be detected by the fluorescence detector. NaOH eluent used in the present method matches well with the maximal fluorescence intensity obtained at alkaline condition for oxidized phenols, thus the addition of specific buffer solution after oxidation encountered in previous report could be eliminated. This process leads to a simplified procedure. The proposed method was sensitive to the limits of detection in the range of 0.4 μg/L and 3.8 μg/L and the limits of quantification between 1.2 μg/L and 13 μg/L due to the strong electro-oxidation capacity of porous titanium electrode, as well as the implementation of time-programmed potential over EC. The linear ranges were 2.0–1.0 × 104 μg/L for pAAP and DMP, and 10–1.0 × 104 μg/L for P, pMP, pHPA, and TBP, respectively. The relative standard deviations range from 0.9% to 4.8%. The utilization of the method was demonstrated by the analysis of real samples. The average spiked recoveries of target analytes in pool water were 81.0–118%.