Hung Ivan, Gan Zhehong
National High Magnetic Field Laboratory, 1800 East Paul Dirac Drive, Tallahassee, FL 32310, USA.
National High Magnetic Field Laboratory, 1800 East Paul Dirac Drive, Tallahassee, FL 32310, USA.
J Magn Reson. 2023 May;350:107423. doi: 10.1016/j.jmr.2023.107423. Epub 2023 Mar 12.
Solid-state NMR of quadrupolar nuclei such as Cl has become a useful tool to characterize polymorphism in pharmaceutical hydrochlorides. The two-dimensional multiple-quantum magic-angle spinning (MQMAS) experiment can achieve isotropic resolution, and separate quadrupolar line shapes for samples with multiple sites but the pulse sequence efficiency is often low, limiting applications due to the intrinsically low NMR signals and rf field from the low gyromagnetic ratios γ. The use of cosine low-power MQMAS pulse sequences and high magnetic fields is presented to push the limit of MQMAS for insensitive low-γ quadrupolar nuclei. The improved efficiency and fields up to 35.2 T enable the acquisition of MQMAS spectra for pharmaceutical samples with multiple Cl sites, large quadrupolar couplings and/or in diluted dosage forms.
诸如氯等四极核的固态核磁共振已成为表征盐酸盐药物多晶型的有用工具。二维多量子魔角旋转（MQMAS）实验可以实现各向同性分辨率，并为具有多个位点的样品分离四极线形，但脉冲序列效率通常较低，由于本质上较低的核磁共振信号和来自低旋磁比γ的射频场而限制了应用。本文介绍了使用余弦低功率MQMAS脉冲序列和高磁场来突破针对不灵敏的低γ四极核的MQMAS极限。提高的效率和高达35.2 T的磁场使得能够采集具有多个氯位点且四极耦合大的药物样品和/或以稀释剂型的MQMAS谱。
