In situ immobilization of covalent organic frameworks on diatomaceous earth for pipette-tip solid-phase microextraction

Solid-phase microextraction (SPME) is essential for analyzing ultra-low concentration samples, such as trace drugs and environmental pollutants. Among various formats, pipette tip-based SPME (PT-SPME) stands out for its advantages in efficiency, automation, and flexibility. However, PT-SPME faces challenges such as material loss, high synthesis costs, and environmental impact. To address these issues, we developed a novel PT-SPME device by synthesizing Schiff-base covalent organic frameworks (COFs) in situ on diatomaceous earth (DE), which served as both a matrix and support. This approach significantly improved stability and reduced COFs consumption by 93.7 %. The DE@COFs were packed into pipette tips with a sandwich-like structure and used to extract polycyclic aromatic hydrocarbons (PAHs), with detection achieved through high-performance liquid chromatography coupled with fluorescence detection (HPLC-FLD). The method exhibited excellent sensitivity, with limits of detection (LODs) ranging from 2.05 to 52.5 pg/mL and limits of quantification (LOQs) from 15.0 to 159 pg/mL. It also demonstrated high accuracy, with recoveries between 87.05 % and 115.86 %, and strong repeatability, making it suitable for trace pollutant analysis in complex matrices This cost-effective and environmentally friendly PT-SPME system enhances extraction efficiency while reducing material usage, providing a practical and innovative solution for trace pollutant analysis in pharmaceutical and environmental applications.