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

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.