Microwave-assisted preparation of a molecularly imprinted monolith combining an imidazolium ionic liquid and POSS for enhanced extraction of baicalin-like compounds in Scutellaria baicalensis by means of in-capillary SPME followed by on-line LC and off-line LC-MS/MS

Abstract

Molecularly imprinted polymers (MIPs) possess target-customized and range-adjustable selectivity, and have attracted increasing researches to develop new synthetic methods and new forms of applications. By wisely choosing functional monomers with interaction with a certain part of the template, and special cross-linkers to enhance the imprinting effect, the resulting MIP could be expected to possess enhanced capture-ability towards the targeted template of one entity or one species. Here, a polymerizable imidazolium-type ionic liquid monomer was investigated to find out how it could enhance the interaction with a flavone-type template in imprinting compared to how it behaved in free solution. And combined with polyhedral oligomeric silsesquioxanes (POSS), the imprinted monolith in capillary with an optimal imprinting factor (IF = 5.4) was used as a capture column in on-line SPME-HPLC and off-line LC-MS/MS. The hybrid-imprinted monolith could selectively capture and enrich baicalin and its analogues in traditional Chinese medicine (TCM) Scutellaria baicalensis for further qualitative and quantitative analysis, with an LOD of 0.001 μg mL⁻¹. Besides, the structural similarities of extracted compounds were parameterized and systematically analyzed for better understanding of the obtained wide selectivity. This work utilized an ionic liquid and POSS combined to enhance the wide selectivity of MIP, which was of potential application in selectively capturing certain compound groups in complex analytes, especially by means of 2-dimensional LC systems.