Nanoporous Polyimide Microspheres Solid Phase Extraction Coupled to Liquid Chromatography with Fluorescence Detection to Determine Fluoroquinolones in Water and Food Samples

In this work, nanoporous polyimide (PI) microspheres (NPMs) were prepared in bulk using the spray phase inversion technique. Due to the right size and shape, open nanopores with diameters of 10–70 nm, a large surface area of 52 m 2  g −1 , and abundant chemical extraction property, these NPMs were successfully used as solid phase extraction (SPE) sorbents. Combined with an ultra-performance liquid chromatography-fluorescence detector (NPM-SPE-UPLC-FLD), five fluoroquinolones (FQs) were quantified successfully in environmental water and food samples. After the NPMs with 50–75 μm diameters were collected by sieving, packed into an SPE cartridge, and conditioned by rinsing with acetonitrile and water, FQs in water samples were extracted and eluted with high recoveries between 75.5% and 112.3%. A breakthrough volume of 380 mL was obtained with only 20 mg of NPM sorbents. Under optimal conditions, the limits of detection for FQs in spiked purified water were 0.002–0.011 μg L −1 , and the linear range was more than three orders of magnitude (0.004–10 μg L −1 ) with good correlation coefficients of 0.9984–0.9996. The intra-batch relative standard deviations (RSDs) of the NPMs were 0.5%–9.8%, and the inter-batch RSDs were 1.6%–13.4%. Finally, the NPM-SPE-UPLC-FLD method was successfully applied to water, egg and milk samples. These results demonstrated that NPMs are promising candidates for SPE sorbents due to their convenient preparation and excellent performance in environmental water and food samples. Graphical abstract