Study On The Determination Of Phenolic Compounds In Water By HPLC With Fluorescence Detector

Objective: A rapid and simple method for simultaneous determination of 12 phenolic compounds in water samples by high performance liquid chromatography with fluorescence detector was developed. The 12 phenolic compounds investigated in this research were hydroquinone, resorcinol, catechol, phenol, p-cresol, m-cresol, o-cresol,α-naphthol,β-naphthol, bisphenol A (BPA), 4-tert- butyphenol (4-t-BP), 4-nonylphenol (4-NP). Solid phase extraction (SPE) and Cloud point extraction (CPE) were evaluated and used as the preconcentration steps of water samples.Method: The chromatographic condition, SPE and CPE procedure were optimized. An analytical method for determination of phenolic compounds in water was established.1. Direct determination of phenolic compounds in water by SPE-HPLC-FLD.The water sample was passed through a SPE-cartddge filled D 101 resin and the phenols were eluted with methanol. The eluant was concentrated by nitrogen stream. A C₁₈ column was used to separate the phenolic compounds in the mobile phase of acetonitrile- ammonium acetate buffer (pH 4.5) at a flow rate of 1.0ml/min. Fluorescence detection with the excitation wavelength at 230nm and 3 emission wavelengths at 320nm, 360nm, 440nm was used for the determination.2. Determination of phenolic compounds in water by CPE-HPLC-FLD.A novel extraction method, the so-called "Cloud point extraction, CPE", was exploited and used for the extraction and preconcentration of phenolic compounds in water prior to their determination by HPLC-FLD. The water sample was filtered, and then was adjusted to pH 4.0. Aliquot of 10ml water sample was transferred to a centrifuge tube, 0.2ml of 50g/L Triton X-114 and 0.2ml of 100g/L NaC1 were added. The water sample was kept in the thermostatic bath at 50℃for 20min. Then the phase separation was accelerated by centrifugation for 10min at 2000rpm. After phase separation, the bulk aqueous phase was removed and make the volume of non-ionic surfactant phase to 0.2ml by adding methanol and then for subsequent HPLC analysis.Results: 1. The separating and analyzing conditions of HPLC as well as the parameters of SPE were optimized. The retention behaviors of the analyts on the C₁₈ column were studied. It showed good linearities in the ranges of 0.1～10.0mg/L for hydroquinone, resorcinol, catechol, phenol and 4-NP, 0.05～5.0 mg/L for m-cresol, p-cresol / o-cresol, BPA and 4-t-BP, 0.025～2.5 mg/L forα-naphthol, 0.001～0.1 mg/L forβ-naphthol. The detection limit of this method is between 0.002μg/L to 0.150μg/L. The recoveries of spiked samples of river water were in the range from 73.9% to 119.0% with relative standard deviation(RSD) of 2.9%～15.1%.2. CPE technique was applied for the extraction of 12 phenolic compounds described as above. The extraction efficiencies decreased as the polarities and water-solubilities of the phenols increased. Under the optimum conditions, the extraction efficiencies ofα-naphthol,β-naphthol were satisfactory and the extraction efficiency of BPA was the best (＞90) in these phenolic compounds. The retention times of the non-ionic surfactant,4-t-BP and 4-NP on C₁₈ column were superposition. In this work, CPE was used to extractα-naphthol,β-naphthol and BPA in water. The proposed method was successfully applied to the real water sample and the spiked recoveries of 64.2%～98.9% and relative standard deviation(RSD) of 1.4%～13.8%were obtained.Conclusion: 1. The proposed method proves to be simple, accurate and specific, thus it can satisfy the requirements of water analysis and suitable for analyzing phenolic compounds in both surface water and drinking water.2. The analytical method based on cloud point extraction and HPLC-FLD was successfully applied to determineα-naphthol,β-naphthol and BPA in water sample. This method does not need special equipment and is simpler, cheaper and suitable for the rapid determination of phenolic compounds in water.