Quantification Studies in Continuous-Flow ¹³C Nuclear Magnetic Resonance Spectroscopy by Use of Immobilized Paramagnetic Relaxation Agents

Abstract

Different types of immobilized free radicals as well as immobilized paramagnetic gadolinium(III) complexes were synthesized and used as relaxation agents to shorten the spin-lattice relaxation times T 1 of analytes in quantitative continuous-flow 13 C nuclear magnetic resonance spectroscopy (NMR). The immobilized paramagnetic relaxation agents were characterized with electron paramagnetic resonance spectroscopy (EPR) and extended X-ray absorption fine structure spectroscopy (EXAFS). With these types of paramagnetic relaxation agents, it was possible to obtain a 4-fold increase in signal-to-noise ratio per unit time, and an almost quantitative NMR spectra in continuous-flow 13 C NMR spectroscopy could be acquired with this method.

Trends in Spectroscopic Techniques for Process Control

“…Novel polarization transfer methods [22], spin-lattice relaxation time reduction techniques [23], and cryogenic NMR probes [24] have been utilized toward the improvement of NMR measurements. Because cryogenic magnets are not compatible with the industrial environment, the development of process capability of such instruments is highly appreciated, for example, by further developing MR NMR and microcoil capillary NMR techniques [25,26].…”

Monitoring the On‐line Titration of Enantiomeric Omeprazole Employing Continuous‐flow Capillary Microcoil 1H NMR Spectroscopy

“…This setup can be used to monitor many reactions. [8][9][10][11][12][13][14][15][16][17][18] All NMR spectra were recorded on a Bruker AMX 600 spectrometer (Bruker BioSpin GmbH, Rheinstetten, Germany). The NMR spectrometer was operated by an O2 workstation (Silicon Graphics) and XWIN-NMR software (Bruker Biospin GmbH, Rheinstetten, Germany).…”

Triterpenes in the hexane extract of leaves of Olea europaea L.: analysis using 13C‐NMR spectroscopy

“…The addition of a paramagnetic relaxation reagent, such as Cr(acac) 3 , provides, by means of an electronic relaxation mechanism, both a decrease in T 1 values and the elimination of the NOE effect. Nevertheless, the line width broadening provoked by the high concentration of paramagnetic compound required to reach this goal is the main drawback of its use with complex mixtures (Mooney, 1989;Fischer et al, 2003). Conversely, quantitative determination can be obtained using a rapid train of short pulses, since a small flip angle provides less difference in the steady-state magnetisation than a larger one in the presence of nuclei having different T 1 values (Blunt and Munro, 1976;Gröne et al, 1998;Kalinowski et al, 1991).…”