Kc Ravi, Henry Ian D, Park Gregory H J, Raftery Daniel
Department of Chemistry, Purdue University, West Lafayette, IN 47907, USA.
J Magn Reson. 2009 Apr;197(2):186-92. doi: 10.1016/j.jmr.2008.12.020. Epub 2008 Dec 25.
Improved NMR detection of mass limited samples can be obtained by taking advantage of the mass sensitivity of microcoil NMR, while throughput issues can be addressed using multiple, parallel sample detection coils. We present the design and construction of a double resonance 300-MHz dual volume microcoil NMR probe with thermally etched 440-nL detection volumes and fused silica transfer lines for high-throughput stopped-flow or flow-through sample analysis. Two orthogonal solenoidal detection coils and the novel use of shielded inductors allowed the construction of a probe with negligible radio-frequency cross talk. The probe was resonated at (1)H-(2)D (upper coil) and (1)H-(13)C (lower coil) frequencies such that it could perform 1D and 2D experiments with active locking frequency. The coils exhibited line widths of 0.8-1.1 Hz with good mass sensitivity for both (1)H and (13)C NMR detection. (13)C-directly detected (2)D HETCOR spectra of 5% v/v (13)C labeled acetic acid were obtained in less than 5 min. Demonstration of the probe characteristics as well as applications of the versatile two-coil double resonance probe are discussed.
通过利用微线圈核磁共振（NMR）的质量灵敏度，可以提高对质量受限样品的NMR检测能力，而通量问题则可以通过使用多个平行样品检测线圈来解决。我们展示了一种双共振300兆赫兹双体积微线圈NMR探针的设计与构建，该探针具有经过热蚀刻的440纳升检测体积以及用于高通量停流或流通样品分析的熔融石英传输线。两个正交的螺线管检测线圈以及屏蔽电感的新颖应用，使得能够构建一个射频串扰可忽略不计的探针。该探针在氢-氘（上部线圈）和氢-碳-13（下部线圈）频率下共振，从而可以在主动锁定频率下进行一维和二维实验。对于氢和碳-13的NMR检测，这些线圈的线宽为0.8 - 1.1赫兹，具有良好的质量灵敏度。在不到5分钟的时间内获得了5%（体积比）碳-13标记乙酸的碳-13直接检测的氘异核相关谱。本文讨论了该探针的特性展示以及这种通用的双线圈双共振探针的应用。
