Preconcentration of tropane alkaloids by a metal organic framework (MOF)-immobilized ionic liquid with the same nucleus for their quantitation in Huashanshen tablets

Abstract

The application of ionic liquids (ILs) for the separation of bioactive compounds from various sample matrices is a burgeoning area. Here, a class of porous materials called metal–organic frameworks (MOFs) were combined with tropine-based ILs having structural similarity with natural tropane alkaloids for the quantitative analysis of Huashansheng tablets. Three MOFs (MIL-101, HKUST-1 and ZIF-8) were used to form the composite with the a tropine-based IL (N-propyl-substituted tropine hexafluorophosphate, [C₃tr][PF₆]), using the ship-in-a-bottle (SIB) synthesis approach. The performance of the hybrid IL/MOF composite (IL@MOF) was evaluated as a potential sorbent for application in the dispersive solid-phase-extraction-based enrichment of tropane alkaloids, followed by chromatographic analysis. It was found that [C₃tr][PF₆]@MIL-101 exhibited excellent adsorption capacity, and the extraction results showed satisfactory recoveries in the range of 91.5–104.7% (RSD < 5%). Further, the limit of detection went down to 10–20 μg L⁻¹ with a linear range from 100–500 μg L⁻¹, which proved that an adsorbent with the same nucleus as the target objects would be more suitable and efficient for their later extraction.