Preparation of functionalized graphene and ionic liquid co-doped polypyrrole solid phase microextraction coating for the detection of benzoates preservatives

A novel solid-phase microextraction coating based on polypyrrole (Ppy) with manganese dioxide modified 6-aminohexanoic acid functionalized graphene (MnO 2 -fGr) and 1-allyl-3-vinylimidazolium bis(trifluoromethylsulfonyl)imide ([AVIm]NTf 2 ) as dopants (Ppy/MnO 2 -fGr/[AVIm]NTf 2 ) was successfully prepared by electrochemical method. The composite coating was characterized by scanning electron microscope (SEM), Fourier infrared spectrum (FT-IR) and thermogravimetry (TG). The composite coating showed coarse structure, which could improve the specific surface area of it, and according to the TG curve, it also had good thermal stability. The composite coating was used for the headspace-solid phase microextraction (HS-SPME) and chromatographic analysis of benzoates (i.e. methyl benzoate , ethyl benzoate, propyl benzoate, butyl benzoate)，by coupling with gas chromatography with hydrogen flame ionization detector (GC-FID). Under optimal conditions, their enrichment factors were 140–460, linear detection ranges were 25–60000 ng L −1 , and detection limits were 2.84–6.42 ng L −1 . The standard deviations for five consecutive extractions of 100 μg L −1 analytes were 3.00–10.20%, while the standard deviation for the extractions of 100 μg L −1 analytes with five different coatings were 5.70–13.80%. The proposed method was applied for the detection of the benzoates in cosmetics, and the recoveries for the spiked benzoates were 82.8–116.8%.