Nanoliter Volume Sample cells for 1H NMR: Application to Online Detection in Capillary Electrophoresis
Nanoliter Volume Sample cells for 1H NMR: Application to Online Detection in Capillary Electrophoresis
复制标题
用于 1H NMR 的纳升体积样品池：在毛细管电泳在线检测中的应用
DOI：
10.1021/ja00096a073
复制
发表时间：
1994
影响因子：
15
通讯作者：
J. Sweedler
中科院分区：
文献类型：
--
作者：
N. Wu;T. L. Peck;A. Webb;R. Magin;J. Sweedler
Capillary electrophoresis (CE) is a powerful method capable of efficient separations of extremely small volume samples. 2-4 Along with the ability to inject and separate nanoliter volumes, the availability of a detection scheme capable of working with such small volume samples is important. 5 NMR, one of the most molecular information rich detection schemes, has not been reported previously as a CE detector. This is primarily due to the inherently low sensitivity of NMR, although NMR micro-probes have been developed for samples as small as 0.4 Mg and 1-10 mL volumes. 6'7 NMR has been used as an on-line detector for HPLC, 8-11 but the detectorcells have been in the 25-200 mL volume range, orders of magnitude larger than acceptable in CE. Here we report the design of an rf microcoil wrapped directly around a fused silica separation capillary that provides a detection cell of~ 5 nL and limits of detection (LODs) in the nanogram range for short (< 1 min) NMR acquisitions. Because of the nearly 3 order of magnitude decrease in sample volume, a host of new applications become amenable to NMR analysis, including the analysis of microgram samples andon-line NMR detection for microseparations. Although there are many applications for such NMR microcells, we have chosen to emphasize the combination of CE and NMR. The combination of NMR and electrophoresis has been demonstrated previously. 12-14 In the work of Johnson and He, 13a large (several hundred microliters) U-tube elecrophoresis system was constructed that allowed the electrophoretic mobilities and diffusion coefficients to be determined for each line in an NMR spectrum (although no separations were performed). However, they had to limit their maximum applied voltage because of joule heating. By scaling down the sample cell volume 3 orders of magnitude, the heating effects are reduced to the point that much higher field strengths can be used. 2-3'15The experiment described here involves wrapping Cu wire around a 75 am id fused silica capillary to form a miniature rf coil (typically with 17 turns for a total 1.1 mm detection length). 16 The capillary and microcoil are mounted in an NMR probe so that the capillary and coil are perpendicular to the static magnetic
