Feb 17, 2025
Quantitative Bloch Decay for Spin-1/2 Nuclei
This protocol is a draft, published without a DOI.
- Alexander L. Paterson1
- 1National Magnetic Resonance Facility at Madison (NMRFAM), University of Wisconsin-Madison, Madison, WI, United States
Protocol Citation: Alexander L. Paterson 2025. Quantitative Bloch Decay for Spin-1/2 Nuclei. protocols.io https://protocols.io/view/quantitative-bloch-decay-for-spin-1-2-nuclei-dfpe3mje
License: This is an open access protocol distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
Protocol status: In development
We are still developing and optimizing this protocol, but it should be functional. We hope to solicit feedback primarily on clarity and usability. We intend to publish it in June 2025.
Created: June 14, 2024
Last Modified: February 17, 2025
Protocol Integer ID: 101830
Keywords: Quantitative MAS Bloch Decay: Spin-1/2
Funders Acknowledgements:
National Science Foundation
Grant ID: 1946970
Abstract
Purpose
To acquire a 1D MAS spectrum of a spin-1/2 nucleus with quantitative intensities.
Scope
The acquisition of 1D NMR spectra of spin-1/2 nuclei with quantitative relative intensities requires attention to be paid to the T1 relaxation of each resonance. This SOP should only be followed when quantitative relative intensities are required. If only lineshapes or chemical shifts are required, the d1 relaxation period can be reduced in duration.
Guidelines
If there is a significant rotor or probe background, an echo sequence may be more appropriate.
The quantitative intensities described here are relative intensities, not absolute intensities. Determining absolute intensities, sometimes known as spin counting, is outside the scope of this SOP.
Materials
Definitions:
- T1: Longitudinal relaxation time constant
Safety warnings
High-power decoupling can cause damage to a probe if applied incorrectly. Ensure that the decoupling power and duration are set within safe limits.
Before start
User should be familiar with the power limitations and duty cycle of the probe being used.
User should be familiar with the maximum safe spinning speed of the probe and rotor being used.
Accurate T1 relaxation times and calibrated pulse lengths must have been obtained prior to starting.
The expected amount of time to completion is highly sample-dependent and cannot be accurately estimated ahead of time.
Procedure
Procedure
Load pulse sequence hpdec.
Set the relaxation time d1 to 5 × T1, where T1 is the largest value previously measured.
Set the pulse length p1 and pulse power plw1 to a previously optimized 90° pulse.
Set the 1H decoupling program, CPDPRG2, pulse length, PCPD2, and pulse power, plw12, to a previously optimized 1H decoupling condition.
If no 1H decoupling is required, set the pulse power plw12 to 0 W.
Set the acquisition time aq to a sufficiently long value such that the FID is not truncated, but less than 50 ms if decoupling is used.
Safety information
Applying high-power decoupling for more than 50 ms can cause physical damage to the probe.
Safety information
Ensure that the relaxation time d1 is long enough to respect the duty cycle of the probe. This typically requires d1 to be at least 20x longer than aq.
Adjust ns to effectively make use of available experimental time while achieving sufficient signal-to-noise ratios.
Note
If a good number for ns cannot be estimated, spectra can be acquired in blocks and added via fidsum.
Process the spectrum while paying careful attention to background subtraction and baseline correction if necessary.
Obtain the relative intensities of the resonances via integration if well-resolved, or deconvolution if not.
Protocol references
Y. Nishiyama and N. T. Duong, “Practical guides for 1H detected solid-state NMR under fast MAS for small molecules,” Journal of Magnetic Resonance Open, vol. 10-11, p. 100062, Jun. 2022.
https://doi.org/10.1016/j.jmro.2022.100062
Protocol
NAME
Saturation Recovery
CREATED BY
NMRFAM Facility