Preparation of Acidity-Sensitive N-Isopropylacrylamide and Methacrylic Acid Copolymer Monolithic Column for the Pipette Tip Solid Phase Extraction of Phenols

An acidity-sensitive poly(N-isopropylacrylamide-methyl acrylic acid-co-divinyl- benzene) monolith was prepared in situ in a pipette tip for solid phase extraction of phenol, m-cresol, o-nitrophenol, 2,4-dichlorophenol and p-tertbutylphenol. The monolith was characterized by FT-IR, BET (surface area - 266.56 m(2)/g) and thermogravimetric analysis (thermally stable up to 350(circle)C). The introduction of methyl acrylic acid enhanced the stability in the strong alkaline condition. The adsorption experiments and density function theory calculations indicated NIPAM was the main adsorption sites and the adsorption mechanism of phenol on the monolith was hydrophobic interaction, H-bond interaction, C - H center dot center dot center dot pi interaction of isopropyl group of NIPAM with the phenyl group of phenols. Based on these features and under the optimal extraction conditions, a pipette tip solid phase extraction coupled to high-performance liquid chromatography with ultraviolet detection method was developed for the determination of 5 phenols in the diffusion of polycarbonate cups. Due to the usage of 0.1 M NaOH as the eluent, the method presented selectivity for phenols based on the acidity-sensitive of the monolith. Wide linear range (0.6-200 mu g/L), low detection limits (0.2-0.3 mu g/L), good reproducibility (%RSD less than 9.8%) and satisfactory recoveries (86.3-114.1%) were obtained. The proposed method was suitable for quantitative analysis of phenollic in water samples.