Related Experiment Video
Updated: Jun 14, 2026
08:55
High-Temperature and High-Pressure In situ Magic Angle Spinning Nuclear Magnetic Resonance Spectroscopy
Published on: October 9, 2020
Breaking the T1 constraint for quantitative measurement in magic angle spinning solid-state NMR spectroscopy
Guangjin Hou1, Shangwu Ding, Limin Zhang
1State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Center for Magnetic Resonance, Wuhan Institute of Physics and Mathematics, the Chinese Academy of Sciences, Wuhan 430071, China.
Journal of the American Chemical Society
|April 2, 2010
Summary
New quantitative solid-state NMR methods overcome T(1) limitations for low-gamma spins. These techniques enable faster, more efficient quantitative analysis by redistributing magnetization, reducing experimental time significantly.
Area of Science:
- Nuclear Magnetic Resonance Spectroscopy
- Solid-State Chemistry
- Materials Science
Background:
- Quantitative solid-state NMR is crucial for materials characterization.
- Long spin-lattice relaxation times (T1) of low-gamma nuclei traditionally limit experimental speed and efficiency.
- Conventional methods require lengthy recycle delays (often 5*T1), hindering throughput.
Purpose of the Study:
- To present novel quantitative solid-state NMR experimental schemes.
- To overcome the T1 constraint for low-gamma spins.
- To enable faster and more efficient quantitative NMR analyses.
Main Methods:
- Development of Quantitative Single Pulse (QUSP) and Quantitative Cross-Polarization (QUCP) schemes.
- Integration of broad-band homonuclear recoupling techniques with standard NMR pulse sequences.
- Utilizing dipolar interactions during a mixing time to redistribute non-uniformly enhanced magnetization.
Main Results:
- Achieved quantitative NMR spectra with recycle delays substantially shorter than the conventional 5*T1.
- Demonstrated that magnetization redistribution leads to a quasi-equilibrium state for uniform enhancement.
- Observed significant efficiency gains in QUSP and QUCP experiments.
Conclusions:
- The developed QUSP and QUCP methods effectively eliminate the T1 constraint for quantitative solid-state NMR.
- These techniques allow for considerably reduced experimental times, especially for low-gamma spin systems.
- The findings pave the way for more rapid and efficient analysis of various materials using NMR.
Related Concept Videos
01:14NMR Spectrometers: Resolution and Error Correction
When magnetic nuclei in a sample achieve resonance and undergo relaxation, the signal detected in NMR is an approximately exponential free induction decay. Fourier transform of an exponential decay yields a Lorentzian peak in the frequency domain. Lorentzian peaks in an NMR spectrum are defined by their amplitude, full width at half maximum, and position, where the peak width is governed by the spin-spin relaxation time alone. In real experiments, however, the applied magnetic field is rendered...
00:52¹H NMR of Conformationally Flexible Molecules: Temporal Resolution
At room temperature, the chair conformer of cyclohexane undergoes rapid ring flipping between two equivalent chair conformers at a rate of approximately 105 times per second. These two chair conformers are in equilibrium. The rapid ring flipping results in the interconversion of the axial proton to an equatorial proton and an equatorial to the axial proton. Such interconversions are too rapid and cannot be detected on the NMR timescale. Hence, the NMR spectrometer cannot distinguish between the...
01:02¹H NMR: Interpreting Distorted and Overlapping Signals
Spin systems where the difference in chemical shifts of the coupled nuclei is greater than ten times J are called first-order spin systems. These nuclei are weakly coupled, and their chemical shifts and coupling constant can generally be estimated from the well-separated signals in the spectrum.
As Δν decreases and the signals move closer, the doublets appear increasingly distorted. The intensities of the inner lines increase at the cost of those of the outer lines as the signals are slanted or...
As Δν decreases and the signals move closer, the doublets appear increasingly distorted. The intensities of the inner lines increase at the cost of those of the outer lines as the signals are slanted or...
01:08NMR Spectroscopy: Spin–Spin Coupling
The spin state of an NMR-active nucleus can have a slight effect on its immediate electronic environment. This effect propagates through the intervening bonds and affects the electronic environments of NMR-active nuclei up to three bonds away; occasionally, even farther. This phenomenon is called spin–spin coupling or J-coupling. Coupling interactions are mutual and result in small changes in the absorption frequencies of both nuclei involved. While nuclei of the same element are involved in...
01:08Spin–Spin Coupling Constant: Overview
In bromoethane, the three methyl protons are coupled to the two methylene protons that are three bonds away. In accordance with the n+1 rule, the signal from the methyl protons is split into three peaks with 1:2:1 relative intensities. The methylene protons appear as a quartet, with the relative intensities of 1:3:3:1.
Qualitatively, any spin plus-half nucleus polarizes the spins of its electrons to the minus-half state. Consequently, the paired electron in the hydrogen–carbon bond must have a...
Qualitatively, any spin plus-half nucleus polarizes the spins of its electrons to the minus-half state. Consequently, the paired electron in the hydrogen–carbon bond must have a...
01:15¹H NMR of Conformationally Flexible Molecules: Variable-Temperature NMR
The axial and equatorial protons in cyclohexane can be distinguished by performing a variable-temperature NMR experiment. In this process, except for one proton, the remaining eleven protons are replaced by deuterium. The deuterium substitution avoids the possible peak splitting caused by the spin-spin coupling between the adjacent protons. The remaining proton flips between the axial and equatorial positions.