Low flow-resistance solid phase extraction of fluoroquinolones in water and food samples by high-pressure wet spinning porous polyimide microfibers.

ABSTRACT

In this work, porous polyimide microfibers (PI-µF) were prepared by high-pressure wet spinning method, and successfully applied as adsorbents for solid phase extraction (SPE) of fluoroquinolones (FQs) in water and food samples. The PI-µFs of ∼10, 25, 50, 100 µm in diameter could be controlled by the inner diameter of quartz capillary nozzles. The flow resistance of SPE cartridges packed with 10 µm PI microfiber (10-PI-µF) and 25-PI-µF was comparable to or even lower than that of commercial SPE cartridges, while the flow resistance of 50-PI-µF and 100-PI-µF SPE cartridges was increased obviously due to tiny broken pieces. The 10-PI-µF and 25-PI-µF have a specific surface area of 102 m2 g-1 and 76 m2 g-1, mesopores of 22-32 nm, and large breakthrough volume of 110 mL/5 mg and 85 mL/5 mg for FQs, while the 50-PI-µF and 100-PI-µF had much lower specific surface area and hardly had retention for FQs. FQs from tap water, egg and milk samples were then extracted by PI-µF SPE, and analyzed by high performance liquid chromatography-fluorescence detector (HPLC-FLD). SPE parameters as type of elution solvent, elution solvent volume, pH value of sample solution, flow rate of sample solution, and breakthrough volume were first optimized in detail. Under the optimal conditions, the PI-µF SPE/HPLC-FLD method showed high recoveries (96.8%-107%), wide linearity (0.05-50 µg L-1, or 0.01-10 µg L-1), high determination coefficients (R2 ≥0.9992), and low limits of detection (LODs, 0.005-0.014 µg L-1). For the real tap water, egg and milk samples, the recoveries and RSDs were 81-119% and 0.8-9.8%, respectively. The results show that porous microfiber up to 25 µm in diameter is a promising solid-phase extraction adsorbent with the lowest flow resistance that can be used for trace organic pollutants in water and food samples.