Cotton thread modified with ionic liquid copolymerized polymer for online in-tube solid-phase microextraction and HPLC analysis of nonsteroidal anti-inflammatory drugs

Cotton fiber is a biodegradable material that possesses properties such as high specific area, adjustable shape, and hygroscopicity. In this work, organic polymer was directly in situ grown on the surface of cotton thread and packed into a poly(ether ether ketone) tube for online in-tube solid-phase microextraction. The novel strategy solves the problems like high backpressure and tedious optimization process of normal monolithic polymer-based in-tube solid-phase microextraction capillary. The quaternary ammonium typed ionic liquid of 1-allyl-methylimidazolium chloride, 4-vinylbiphenyl, and ethylene dimethacrylate were co-polymerized and in situ grown on the surface of cotton thread as extraction phase. The solid-phase microextraction tube showed excellent performance for the extraction of three nonsteroidal anti-inflammatory drugs including ketoprofen, naproxen, and flurbiprofen due to the strong ion exchange and hydrophobic interactions. After online coupling with a high-performance liquid chromatography system by six-port valve, the method was applied for the quantitative analysis of nonsteroidal anti-inflammatory drugs in human plasma samples showing good enrichment performance (enrichment factor between 263 and 279), high sensitivity, good linearity, and good reproducibility.