zn mof/cof composite as an effective adsorbent for solid-phase microextraction sampling of pahs from soil samples

By hybridization of zinc-based metal-organic framework-5 (mof-5) and melamine-terephthaldehyde-based two-dimensional π-conjugated covalent organic framework (cof), a novel mof-5/cof (m5c) nanocomposite was prepared. m5c was carried out for efficient solid-phase microextraction (spme) sampling of ultratrace trace levels of polycyclic aromatic hydrocarbons (pahs) from soil samples prior to their separation and determination by gc-fid [1, 2]. the adsorbent was characterized by fourier transform infrared spectrometry, x-ray diffractometry, scanning electron microscopy, thermal gravimetric analysis, and nitrogen adsorption-desorption. a box-behnken design (bbd) was carried out to evaluate the variables affecting the extraction efficiency [3]. under the optimum conditions, the proposed method showed low limits of detection (lods, 0.006–0.54 μg g−1), wide linear ranges (0.02–2000 μg g−1), and good repeatability with relative standard deviations (rsds) of 0.11–4.93% for single fiber and 0.42%–7.36% for fiber-to-fiber. the spiked recoveries at two levels of 20 and 50 μg g−1 were in the range of 76.5–112.0% with the rsds less than 8.3%. compared with commercial fibers, the homemade fiber displayed excellent extraction capacity. the zn mof/cof coating was stable over 120 successive cycles of extraction/desorption without significant loss of extraction efficiency. the method was successfully applied for the determination of pahs in real soil samples.