Cu@ZIF-8 coupled to UPLC-UV for rapid and sensitive analysis of emodin and rhein in urine samples

This study presented the development of a novel adsorbent system through the synthesis of cationic surfactant-modified Cu-doped ZIF-8 (Cu@ZIF-8), leveraging the synergistic advantages of bimetallic-enhanced surface area and surfactant-mediated stability. Among various surfactants evaluated, dodecyltrimethylammonium bromide (DTAB)-functionalized Cu@ZIF-8 exhibited superior adsorption performance toward emodin and rhein, driven by combined π-π interactions and hydrogen bonding. This optimized adsorbent facilitated the development of an innovative analytical method integrating Cu@ZIF-8-based extraction with UPLC-UV for the trace-level quantification of target analytes in complex biological matrices. Comprehensive optimization of critical extraction and desorption parameters yielded a robust analytical protocol with excellent linearity (0.05–5.00 μg/mL; R² = 0.9993 and 0.9980), sensitive detection limits (0.01 μg/mL), and satisfactory recovery (92.73–108.86 %). The validated method successfully characterized the urinary pharmacokinetic profiles of emodin and rhein following rhubarb extract administration in rats. Compared to conventional protein precipitation approaches, this approach offers significant advantages in simplicity, analysis speed and environmental compatibility. These findings position surfactant-engineered Cu@ZIF-8 as a promising platform for bioanalytical applications, particularly in the quantification of anthraquinone derivatives in biological specimens.