Boric acid functionalized spherical covalent organic frameworks as an online extraction adsorbent for the selective...

In this work, a novel spherical boronic acid-functionalized covalent organic framework (COF) was designed and synthesized via a facile two-step strategy. This approach involved the construction of a vinyl-functionalized COF (TpbDva), followed by the covalent grafting of 4-mercaptophenylboronic acid through a thiol-ene click reaction, yielding the target material, denoted as TpbDva-PBA. The resulting COF has a uniform spherical morphology, high specific surface area, and excellent chemical stability, along with the specific molecular recognition capability of boronic acid toward cis-diol compounds. Leveraging this synergistic effect, an online solid-phase extraction method coupled with high-performance liquid chromatography-diode array detection (HPLC-DAD) was developed for the selective enrichment and determination of three nucleosides (adenosine, guanosine, and uridine). Under optimal conditions, the method exhibited a wide linear range of 1.00-100.00 μg L^-1 (R ≥ 0.9990) and high sensitivity, with limits of detection (LODs, S/N ≥ 3) ranging from 0.35 to 1.00 μg L^-1. The relative standard deviations (RSDs, n = 5) for repeatability ranged from 3.7% to 8.8%. The method was successfully applied to the online analysis of trace nucleosides in human urine and mouse plasma samples. Guanosine and adenosine were detected at concentrations of 71.70 and 60.04 μg L^-1 in urine, and 233.2 and 51.24 μg L^-1 in plasma, respectively. The method demonstrated good accuracy, with spiked recoveries ranging from 78.53% to 107.1% (urine) and 76.90% to 98.09% (plasma), and satisfactory precision (RSDs: 1.3-5.3% and 1.3-8.4%; n = 5). This work not only provides an efficient strategy for synthesizing functionalized COFs with enhanced selectivity but also offers a versatile platform for the trace analysis of cis-diol-containing biomarkers in complex biological matrices.