Multinuclear nanoliter one-dimensional and two-dimensional NMR spectroscopy with a single non-resonant microcoil

Raluca M Fratila,M Victoria Gomez,Stanislav Sýkora,Aldrik H Velders

doi:10.1038/ncomms4025

Abstract

Nuclear magnetic resonance (NMR) spectroscopy is a powerful analytical technique, but its low sensitivity and highly sophisticated, costly, equipment severely constrain more widespread applications. Here we show that a non-resonant planar transceiver microcoil integrated in a microfluidic chip (detection volume 25 nl) can detect different nuclides in the full broad-band range of Larmor frequencies (at 9.4 T from 61 to 400 MHz). Routine one-dimensional (1D) and two-dimensional (2D), homo- and heteronuclear experiments can be carried out using the broad-band coil set-up. Noteworthy, heteronuclear 2D experiments can be performed in a straightforward manner on virtually any combination of nuclides (from classical ¹H-¹³C to more exotic combinations like ¹⁹F-³¹P) both in coupled and decoupled mode. Importantly, the concept of a non-resonant system provides magnetic field-independent NMR probes; moreover, the small-volume alleviates problems related to field inhomogeneity, making the broad-band coil an attractive option for, for example, portable and table-top NMR systems.

Highlights

Nuclear magnetic resonance (NMR) spectroscopy is a powerful analytical technique, but its low sensitivity and highly sophisticated, costly, equipment severely constrain more widespread applications
Broad-Band Coil (BBC) microfluidic NMR chip with a 25 nl detection volume and an integrated planar spiral single transceiver coil directly coupled to a coaxial cable, i.e., without any tuning or matching capacitors (Fig. 1a–c; for details on design and fabrication, see Methods and Supplementary Fig. 1), which performs well over the full broad radio frequency (RF) band relevant for NMR at 9.4 T
The normalized 1H molar sensitivity of the non-tuned BBC probe was of 6,546 signal-to-noise ratio (SNR) mmol 1 s 1/2, which is four times higher than the value reported for a 620 nl 1H-tuned microsolenoid probe and B50 times higher than the one reported for a 5-mm commercial probe[8]

Summary

Introduction

Nuclear magnetic resonance (NMR) spectroscopy is a powerful analytical technique, but its low sensitivity and highly sophisticated, costly, equipment severely constrain more widespread applications. We show that a non-resonant planar transceiver microcoil integrated in a microfluidic chip (detection volume 25 nl) can detect different nuclides in the full broad-band range of Larmor frequencies (at 9.4 T from 61 to 400 MHz). The concept of a non-resonant system provides magnetic fieldindependent NMR probes; the small-volume alleviates problems related to field inhomogeneity, making the broad-band coil an attractive option for, for example, portable and table-top NMR systems. The low sensitivity of NMR spectroscopy severely constrains its applications, for mass- and volume-limited samples. For heteronuclear and multidimensional NMR experiments, sophisticated and complex electronic circuitry is required[17,18], which limits the more widespread application and implementation of (microcoil)

Methods

Results

Conclusion