Remotely Detected NMR for the Characterization of Flow and Fast Chromatographic Separations Using Organic Polymer Monoliths

Abstract

An application of remotely detected magnetic resonance imaging is demonstrated for the characterization of flow and the detection of fast, small molecule separations within hypercrosslinked polymer monoliths. The hyper-cross-linked monoliths exhibited excellent ruggedness, with a transit time relative standard deviation of less than 2.1%, even after more than 300 column volumes were pumped through at high pressure and flow. Magnetic resonance imaging enabled high-resolution intensity and velocity-encoded images of mobile phase flow through the monolith. The images confirm that the presence of a polymer monolith within the capillary disrupts the parabolic laminar flow profile that is characteristic of mobile phase flow within an open tube. As a result, the mobile phase and analytes are equally distributed in the radial direction throughout the monolith. Also, in-line monitoring of chromatographic separations of small molecules at high flow rates is shown. The coupling of monolithic chromatography columns and NMR provides both real-time peak detection and chemical shift information for small aromatic molecules. These experiments demonstrate the unique power of magnetic resonance, both direct and remote, in studying chromatographic processes.

Applications of optically detected MRI for enhanced contrast and penetration in metal

“…Therefore, the 2D images explain how the flow profiles for the steel samples are narrower compared with the blank sample. The flow behavior observed in this work is similar to the results of a high-field MRI study on porous organic polymers [38].…”

Effect of hypercrosslinking conditions on pore size distribution and efficiency of monolithic stationary phases

“…The hypercrosslinked stationary phases have been used in capillary LC , CEC , modified with gold nanoparticles , or used as a stationary phases in TLC of peptides and proteins . Besides the classical chromatography techniques, the internal structure of hypercrosslinked monoliths has also been characterized by novel techniques, including magnetic resonance imaging or serial block‐face SEM .…”

“…In our previous works , hypercrosslinked monolithic stationary phases have been prepared using a poly(styrene‐ co ‐vinylbenzyl chloride‐ co ‐divinylbenzene) precursor monolith that was swollen in 1,2‐dichloroethane (DCE) and hypercrosslinked via Friedel–Crafts reaction catalyzed by ferric chloride. The composition of the polymerization mixture used for a preparation of generic monolith controls the efficiency of hypercrosslinked poly(styrene‐ co ‐vinylbenzyl chloride‐ co ‐divinylbenzene) columns.…”

Current trends in the development of porous polymer monoliths for the separation of small molecules

“…Scanning ion conductance microscopy and confocal Raman spectroscopy imaging were used to characterize polymer‐based monolithic stationary phases in solvated states. By using LC–NMR, we were even able to characterize flow‐profile of the mobile phase through hypercross‐linked monolithic stationary phases and found nearly plug‐like profile . Stasses et al characterized porous properties of commercially available poly(styrene‐ co ‐divinylbenzene) monolithic stationary phases by a total‐pore‐blocking method where pores with stagnant mobile phase are blocked by strongly hydrophobic compound (dodecane).…”