Temperature-response polymer coating for in-tube solid-phase microextraction coupled to high-performance liquid chromatography

The silica nanoparticle (SiO 2 NP)-deposited capillary fabricated by liquid phase deposition (LPD) was bonded by 3-(triethoxysilyl) propyl methacrylate and then modified with poly(N-isopropylacrylamide) (PNIPAAm) by polymerization. The resulting PNIPAAm modified SiO 2 NP-deposited capillary was applied to in-tube solid-phase microextraction coupled to high-performance liquid chromatography (in-tube SPME–HPLC). To investigate the extraction performance of the prepared capillary, diethylstilbestrol (DES) with moderate polarity was selected as the model analyte. Results demonstrate that PNIPAAm modified SiO 2 NP-deposited capillary exhibited obvious temperature responsive character. Finally, the PNIPAAm modified SiO 2 NP-deposited capillary was applied to the analysis of three synthetical estrogens from milk samples. The detection limit of the method was found to be in the range 1.2–2.2   ng/g, and recovery was 71.7–98.9% with relative standard deviations in the range of 2.8–12.6%.