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Nanoliter volume, high-resolution NMR microspectroscopy using a 60-micron planar microcoil
J E Stocker1, T L Peck, A G Webb
1Department of Electrical and Computer Engineering, University of Illinois, Urbana-Champaign, USA.
IEEE Transactions on Bio-Medical Engineering
|November 14, 1997
Summary
High-resolution 1H nuclear magnetic resonance (NMR) microspectroscopy is now possible using optimized planar microcoils. These microcoils achieve high signal-to-noise ratio (SNR) and spectral resolution, enabling cellular-level NMR studies.
Area of Science:
- Analytical Chemistry
- Spectroscopy
- Microscopy
Background:
- Previous studies showed planar spiral microcoils (100-micron inner diameter) are feasible for 1H NMR microspectroscopy.
- However, poor spectral resolution and low signal-to-noise ratio (SNR) limited high-resolution applications.
Purpose of the Study:
- To overcome limitations of previous microcoil NMR detectors.
- To achieve high-resolution 1H NMR microspectroscopy using optimized microcoils and materials.
Main Methods:
- Optimized microcoil geometry (60-micron inner diameter, 200-micron outer diameter, 3.5 turns) on a gallium arsenide substrate.
- Used nonconductive liquid fluorocarbon (FC-43) to minimize susceptibility mismatch.
- Positioned a fused silica capillary (75-micron inner diameter) containing the sample 50 microns above the microcoil, analyzing ~1 nL volume.
Main Results:
- Achieved a SNR of 25 (per acquisition) and spectral linewidth < 2 Hz for water at 5.9 T (250 MHz).
- Demonstrated feasibility of high-resolution 1H NMR microspectroscopy with planar microcoils.
- Obtained excellent performance with optimized microcoil design and FC-43.
Conclusions:
- Optimized planar microcoils enable high-resolution 1H NMR microspectroscopy.
- Microcoils are suitable for localized NMR studies at the cellular level.
- Potential applications include capillary electrophoresis and microbore liquid chromatography detectors.