Apparatus for the measurement of transient species and effects in flowing systems by high-resolution nuclear magnetic resonance spectroscopy

Reaction characterization by flow NMR: quantitation and monitoring of dissolved H2via flow NMR at high pressure

“…Application of this technique for accurate quantitation does require consideration of several factors described in previous reports of flow NMR analysis. 7,8 Recent published examples of quantitative flow NMR do not specifically describe these factors, which may significantly impact accuracy if not addressed or compensated for in the experimental design. 9 An illustration of the instrumental configuration used for this work is shown in Fig.…”

Continuous Flow 1H and 13C NMR Spectroscopy in Microfluidic Stripline NMR Chips

“…The apparent relaxation delays of the experiment are affected, as both the observed spin–lattice relaxation time ( T 1 obs ) and the observed spin–spin relaxation time ( T 2 obs ) decrease. 35,41,42 The stationary value of T 1 reflects the time constant for the spins to return to thermal equilibrium after receiving an rf pulse, which poses limitations on the repetition rate. However, when the analyte flows through the detection area during acquisition, the spins can be refreshed faster than the stationary value of T 1 , the acquisition delay between scans can be shortened.…”

“…When the residence time of spins in the detection coil decreases, the effective decay time of the FID decreases, so that the observed relaxation time T 2 obs decreases as well. 42 The observed relaxation time depends on the residence time τ and the stationary value of the relaxation time T 2 stat : . For the smallest detection volume (145 nL) and the highest flow rates (15 μL/min), an estimated increase of ∼0.4 Hz can be expected for line widths of approximately 3 Hz (full-width at half-maximum).…”

Engineering aspects of FlowNMR spectroscopy setups for online analysis of solution-phase processes

“…2 illustrates an example using Bruker's InsightMR™ flow tube that may be inserted top-down into a standard NMR spectrometer with a 5 mm or 3 mm probe head. Its design is based on previously published in-out tube assemblies 31,32,53,54 that inject the sample near the bottom of a cylindrical glass tube from where it flows upwards around the central injection capillary and out of the tube again. Alternative designs using flow-through cells and flow probes have been developed [55][56][57] but few are currently commercially available.…”

“…In this article we shall focus on closed-loop FlowNMR setups for investigating batch processes, but many of the considerations discussed will be relevant to continuous flow application as well. 26,27 A number of flow devices have been developed that allow a continuous stream of sample solution to be pumped through the NMR active region of the spectrometer, [28][29][30][31][32][33][34][35][36] developments that actually date back to early days of NMR spectroscopy in the 1950s. 37 Recent examples include the use of FlowNMR coupled with oxygen probes in the elucidation of the mechanism of amination reactions, 38 the development of low-volume flow system containing biological organisms within the flow tip for solution-state in vivo NMR, 39 the use of ultra-fast single scan 2D NMR in flow 40 and the real-time monitoring of oxidative wastewater treatment.…”