Solid-State NMR 13 C sensitivity at high magnetic field.

Autor: Han R; Department of Chemistry, University of Wisconsin-Madison, Madison, WI, United States., Borcik CG; Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, United States., Wang S; National Magnetic Resonance Facility at Madison (NMRFAM), University of Wisconsin-Madison, Madison, WI, United States., Warmuth OA; Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, United States., Geohring K; BlueSky NMR, Fort Collins, CO, United States., Mullen C; Phoenix NMR, Loveland, CO, United States., Incitti M; Phoenix NMR, Loveland, CO, United States., Stringer JA; Phoenix NMR, Loveland, CO, United States., Rienstra CM; Department of Chemistry, University of Wisconsin-Madison, Madison, WI, United States; Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, United States; National Magnetic Resonance Facility at Madison (NMRFAM), University of Wisconsin-Madison, Madison, WI, United States. Electronic address: crienstra@wisc.edu.
Jazyk: angličtina
Zdroj: Journal of magnetic resonance (San Diego, Calif. : 1997) [J Magn Reson] 2024 Aug; Vol. 365, pp. 107709. Date of Electronic Publication: 2024 Jun 18.
DOI: 10.1016/j.jmr.2024.107709
Abstrakt: Sensitivity is the foundation of every NMR experiment, and the signal-to-noise ratio (SNR) should increase with static (B 0 ) magnetic field, by a proportionality that primarily depends on the design of the NMR probe and receiver. In the low B 0 field limit, where the coil geometry is much smaller than the wavelength of the NMR frequency, SNR can increase in proportion to B 0 to the power 7/4. For modern magic-angle spinning (MAS) probes, this approximation holds for rotor sizes up to 3.2 mm at 14.1 Tesla (T), corresponding to 600 MHz 1 H and 151 MHz 13 C Larmor frequencies. To obtain the anticipated benefit of larger coils and/or higher B 0 fields requires a quantitative understanding of the contributions to SNR, utilizing standard samples and protocols that reproduce SNR measurements with high accuracy and precision. Here, we present such a systematic and comprehensive study of 13 C SNR under MAS over the range of 14.1 to 21.1 T. We evaluate a range of probe designs utilizing 1.6, 2.5 and 3.2 mm rotors, including 24 different sets of measurements on 17 probe configurations using five spectrometers. We utilize N-acetyl valine as the primary standard and compare and contrast with other commonly used standard samples (adamantane, glycine, hexamethylbenzene, and 3-methylglutaric acid). These robust approaches and standard operating procedures provide an improved understanding of the contributions from probe efficiency, receiver noise figure, and B 0 dependence in a range of custom-designed and commercially available probes. We find that the optimal raw SNR is obtained with balanced 3.2 mm design at 17.6 T, that the best mass-limited SNR is achieved with a balanced 1.6 mm design at 21.1 T, and that the raw SNR at 21.1 T reaches diminishing returns with rotors larger than 2.5 mm.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
(Copyright © 2024 Elsevier Inc. All rights reserved.)
Databáze: MEDLINE
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