Simultaneous detection of eight phenols in food contact materials after electrochemical assistance solid-phase microextraction based on amino functionalized carbon nanotube/polypyrrole composite

An electrochemical assistance solid-phase microextraction (EA-SPME) was developed based on amino functionalized multi-walled carbon nanotube/polypyrrole (MWCNTs-NH2/PPy) composite coating. It was applied for the extraction of eight phenols in food contact material, including 2-chlorophenol, o-cresol, m-cresol, 2,4-dichlorophenol, 4-tert-butylphenol, 4-chlorophenol, 4-tertoctylphenol and alpha-naphthol. MWCNTs-NH2/PPy coating was characterized by scanning electron microscopy, transmission electron microscope, X-ray energy spectrometer, X-ray diffraction, Fourier transform infrared and thermogravimetric analysis. The adsorption mechanism of phenols on the composite coatings was investigated. The coating modified steel-wire as an extraction fiber has good electroconductibility, reproducibility and long service life. A determination method for the eight phenols was established by EA-SPME coupled with gas chromatography-flame ionization detection. Under the optimal experimental conditions (extraction temperature: 40 °C; extraction time: 30 min; stirring rate: 600 rpm; NaCl concentration: 0.15 g mL−1; desorption temperature: 250 °C and desorption time: 4 min), the detection linear range was 0.005–50 μg L−1 (R2>0.99), and the detection limit was 0.001–0.1 μg L−1 (S/N = 3). For the quintuple analysis of 50 μg L−1 phenols, the single fiber RSDs were 2.2–12.4%, and the fiber-to-fiber RSDs were 1.9–10.5%. The method was used to detect the migration quantity of the eight phenols from five canned packaging materials, which showed satisfactory recovery 87.3–118.9%.