Enhanced NMR Detection of Mass -Limited Samples With Microcoil Probes: Increasing Sample Throughput and Improved on-Line Coupling to Microscale Separations
Providing structural data unattainable by any other method, nuclear magnetic resonance (NMR) spectroscopy stands as an integral component of the modern academic and industrial chemical laboratory. The development of microcoils enables NMR analysis of small-volume, mass-limited samples. With their diminutive size, multiple microcoils can be situated in a single NMR probe. Enabling simultaneous spectral acquisition from different analytes, multiple microcoil probes can increase NMR throughput for mass-limited samples. By wrapping the coil directly onto fused-silica capillary, microcoil NMR can be easily integrated on-line to microscale separation techniques. As one example, microcoil NMR has been coupled to capillary isotachophoresis (cITP), a form of capillary electrophoresis that can concentrate charged analytes over 100-fold. Consequently, for dilute charged analytes buried in complex mixtures, cITP can isolate and concentrate the charged analytes before presentation to the microcoil, thereby enabling easier structural determination. Demonstrating its strong potential for trace impurity analysis, cITP/NMR successfully analyzes a charged pharmacological agent obscured by a 1000-fold excess of a neutral species. Also benefiting natural product studies, a neurotoxin extracted from a marine organism has been characterized by cITP/NMR. Application of microcoil NMR detection to other separation methods, such as capillary liquid chromatography, will be presented.
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign