Efficient solid-phase extraction of quaternary ammonium alkaloids from traditional Chinese medicines on a novel sulfonic acid group functionalized microporous organic network coated SiO2 composite.

In this work, a novel sulfonic acid-functionalized microporous organic network-coated SiO2 composite (SiO2@MON-SO3H-2) was synthesized for efficient solid-phase extraction (SPE) of quaternary ammonium alkaloids (QAAs) from complex traditional Chinese medicine (TCM) samples. The material exhibits a high specific surface area (381.4 m2 g-1), superhydrophilicity, and excellent stability. These properties, combined with synergistic interactions such as electrostatic attraction, hydrophobic effects, and π-π stacking, enabled the adsorbent to demonstrate outstanding extraction performance toward four typical QAAs. The developed method owns wide linear ranges (0.88-1000 μg L-1) with good linearity (R2 > 0.999), high sensitivity (limits of detection: 0.26-1.02 μg L-1), satisfactory precision (intra- and inter-day RSDs < 6.3%), high enhancement factors (> 91), and insignificant matrix effects (86.6-115.3%). The material maintained excellent reusability, with recoveries remaining above 89% after 50 extraction-desorption cycles. When applied to spiked herbal matrices, the method provided recoveries of 92.7-112.0%. SiO2@MON-SO3H-2 also gave higher recovery than commercial C18, activated carbon, macroporous adsorption resin AB-8, and the cation-exchange resin Amberlite 732. The present work demonstrates the prospect of SiO2@MON-SO3H-2 for trace QAAs extraction from complex samples and provides a reliable approach for TCM analysis and quality control.