Slice‐selected LED and BPPLED: application of slice selection to DOSY

Abstract

High-resolution DOSY (Diffusion-ordered spectroscopy) is a series of 2-dimensional and 3-dimensional NMR techniques based on the differing diffusivity of constituent molecules in the solution state, with which the individual NMR spectrum of each component in a chemical mixture can be observed. All of the DOSY pulse sequences are derived from the spin-echo or stimulated-echo techniques under the effect of PFG (pulsed field gradient). One of the requirements for successful DOSY experiments and data fitting is that PFG must be uniform across the active sample volume. However, PFG, in general, is not uniform across the active sample volume in commercial high-resolution NMR probes and this nonuniformity of PFG is known to produce systematic errors in DOSY experiments. In fact, a strong and uniform gradient field can be realized only in the central region of the gradient coil and the slice-selection technique, widely used in Magnetic Resonance (MR) imaging, can be employed in resolving problems associated with the nonuniformity of PFG. We have developed a slice-selection pulse block, which can be generally applied to any DOSY pulse sequence with proper care of the phase cycling and experimental parameters. We applied the slice-selection technique to LED and BPPLED pulse sequences, which are among the most popular DOSY pulse sequences, and obtained good experimental results for a chemical mixture.

Mobility of Water and Polymer Species and Rheological Properties of Supramolecular Polypseudorotaxane Gels Suitable for Bone Regeneration

“…Binary and ternary polypseudorotaxane systems were prepared by dispersion of the components in water (adding the components in different sequences) and subsequent freeze-drying. The samples were reconstituted with H 2 O:D 2 O mixtures, and diffusion coefficients of the components and solvent were measured using sequences One-shot 21 and SL-DOSY, 22 respectively. The accessibility of the water solvent to the components was measured using a waterLogsy experiment.…”

DOSY NMR applied to analysis of flavonoid glycosides from Bidens sulphurea

“…[21] The best DOSY sequences have Stejskal-Tanner [24] diffusion delay and use bipolar gradient pulses to facilitate phase coherence [2,7,25] and two additional gradient pulses to eliminate eddy currents that can form around the gradient coil, reducing artifacts. [11,26,27] Thus, with a DOSY experiment, the components of a solution can be distinguished without previous separation.…”

“…[2,5,11 -20] The pulse sequences used in a DOSY experiment are based on the PGSE NMR [11,15,21 -23] method and Hahn's nuclear spin echo and has five stages: excitation (net magnetization becomes detectable by the application of a 90 • rf pulse), encoding (applying the first gradient pulse to encode the spin initial positions), evolution (diffusion delay time, , allows the spin translational displacement), decoding (applying a gradient pulse identical to the first one to refocus those spins that did not migrate during the time ) and acquisition of the signal. [21] The best DOSY sequences have Stejskal-Tanner [24] diffusion delay and use bipolar gradient pulses to facilitate phase coherence [2,7,25] and two additional gradient pulses to eliminate eddy currents that can form around the gradient coil, reducing artifacts. [11,26,27] Thus, with a DOSY experiment, the components of a solution can be distinguished without previous separation.…”

A resorcin[4]arene hexameric capsule as a supramolecular catalyst in elimination and isomerization reactions

“…The progress of the reaction was monitored by 1 H NMR and GC–MS by periodic sampling of the solution. Product assignments in the 1 H NMR spectra were carried out in accordance with literature data: for citronellal isomerization products [ 72 – 75 ], for 1,1-diphenylethene [ 76 ], for pinenes isomerization products [ 77 – 78 ].…”