School of Chemistry, University of Southampton, Highfield Campus, Southampton SO17 1BJ, UK.
Lab Chip. 2014 May 21;14(10):1678-85. doi: 10.1039/c3lc51431e. Epub 2014 Mar 24.
High-resolution proton NMR spectroscopy is well-established as a tool for metabolomic analysis of biological fluids at the macro scale. Its full potential has, however, not been realised yet in the context of microfluidic devices. While microfabricated NMR detectors offer substantial gains in sensitivity, limited spectral resolution resulting from mismatches in the magnetic susceptibility of the sample fluid and the chip material remains a major hurdle. In this contribution, we show that susceptibility broadening can be avoided even in the presence of substantial mismatch by including suitably shaped compensation structures into the chip design. An efficient algorithm for the calculation of field maps from arbitrary chip layouts based on Gaussian quadrature is used to optimise the shape of the compensation structure to ensure a flat field distribution inside the sample area. Previously, the complexity of microfluidic NMR systems has been restricted to simple capillaries to avoid susceptibility broadening. The structural shimming approach introduced here can be adapted to virtually any shape of sample chamber and surrounding fluidic network, thereby greatly expanding the design space and enabling true lab-on-a-chip systems suitable for high-resolution NMR detection.
高分辨率质子核磁共振波谱技术是一种在宏观尺度上对生物流体进行代谢组学分析的成熟工具。然而，在微流控器件的背景下，其全部潜力尚未得到充分发挥。尽管微加工的 NMR 探测器在灵敏度方面有了很大的提高，但由于样品流体和芯片材料的磁化率不匹配而导致的有限的光谱分辨率仍然是一个主要障碍。在本研究中，我们通过在芯片设计中加入适当形状的补偿结构，即使在存在显著不匹配的情况下，也可以避免磁化率展宽。基于高斯求积的任意芯片布局的磁场图计算的有效算法被用于优化补偿结构的形状，以确保样品区域内的磁场分布平坦。在此之前，微流控 NMR 系统的复杂性被限制在简单的毛细管中，以避免磁化率展宽。这里介绍的结构匀场方法可以适应几乎任何形状的样品腔和周围的流体网络，从而大大扩展了设计空间，并实现了适用于高分辨率 NMR 检测的真正的片上实验室系统。
