Department of Physics, Volga State University of Technology, Yoshkar-Ola, Russian Federation.
Department of Food Engineering, Middle East Technical University, Ankara, Turkey.
Magn Reson Chem. 2019 Sep;57(9):607-615. doi: 10.1002/mrc.4866. Epub 2019 Jun 6.
Time-domain nuclear magnetic resonance techniques are frequently used in polymer, pharmaceutical, and food industries as they offer rapid experimentation and generally do not require any considerable preliminary sample preparation. Detection of solid and liquid fractions in a sample is possible with the free induction decay (FID). However, for the classical FID sequence that consists of a single pulse followed by relaxation decay acquisition, the dead time of the probe (ring out of resonance circuitry) occurs and varies between 5 and 15 μs for standard 10-mm tubes. In such a case, there arises a risk that the signal from the solid fraction cannot be detected correctly. To obtain quantitative measurement on crystalline and more mobile amorphous fractions, alternative sequences to the classical FID in the solid-state nuclear magnetic resonance were developed. Solid echo and magic sandwich echo sequences perform the relaxation decay refocusing somehow excluding the dead time problem and allow detection of the signal from the solid fraction. In this study, knowledge of amorphous/crystal fraction, which is obtained through solid echo and magic sandwich echo, has been explored on powder sugar samples for the purpose of developing a groundwork for a reliable quality control method. Different sugars were examined for the utilization of the sequences. What is important to add and make this study unique is that the method proposed did not involve multiparameter fitting of the "bead" pattern FID signal that normally suffers from ambiguity; just the integration of the fast Fourier transform of the solid echo was needed to calculate the second moment, (M ).
时域核磁共振技术在聚合物、制药和食品行业中经常被使用，因为它们提供了快速的实验，通常不需要进行任何相当大的初步样品制备。通过自由感应衰减（FID）可以检测样品中的固相与液相。然而，对于由单个脉冲后跟随弛豫衰减采集组成的经典 FID 序列，探头的死时间（共振电路的关闭）会发生，对于标准的 10mm 管，其范围在 5 到 15 μs 之间。在这种情况下，可能存在无法正确检测固相信号的风险。为了对结晶相和更具流动性的无定形相进行定量测量，在固态核磁共振中开发了替代经典 FID 的序列。固体回波和魔角夹心回波序列以某种方式执行弛豫衰减重聚焦，从而排除了死时间问题，并允许检测固相信号。在这项研究中，为了为可靠的质量控制方法奠定基础，探索了通过固体回波和魔角夹心回波获得的无定形/结晶相分数的知识，用于糖粉样品。研究了不同的糖以利用这些序列。值得添加并使这项研究独一无二的是，所提出的方法不涉及通常会受到歧义影响的“珠状”图案 FID 信号的多参数拟合，只需要对固体回波的快速傅里叶变换进行积分，以计算二阶矩（M ）。
