Real-Time 2D NMR Identification of Analytes Undergoing Continuous Chromatographic Separation

We have recently proposed and demonstrated an approach that enables the acquisition of multidimensional nuclear magnetic resonance (NMR) spectra within a single scan. A promising application opened up by this new accelerated form of data acquisition concerns the possibility of monitoring in real time the chemical nature of analytes subject to a continuous flow. The present paper illustrates such potential, with the real-time acquisition of a series of 2D 1H NMR spectra arising from a mixture of compounds subject to a continuous liquid chromatography (LC) separation. This real-time 2D NMR identification of chemicals eluted minutes apart under usual LC−NMR conditions differs from the way in which LC−2D NMR has hitherto been carried out, which relies on stopped-flow modes of operations whereby fractions are first collected and then subject to individual, aliquot-by-aliquot analyses. The real-time LC−2D NMR experiment hereby introduced can be implemented in a straightforward manner using modern commercial LC−NMR hardware, thus opening up immediate possibilities in high-throughput characterizations of complex molecules.