A temperature-controlled sample shuttle for field-cycling NMR

Andrew M.R Hall,Topaz A.A Cartlidge,Giuseppe Pileio

doi:10.1016/j.jmr.2020.106778

Andrew M.R Hall, Topaz A.A Cartlidge + Show 1 more

Open Access

https://doi.org/10.1016/j.jmr.2020.106778

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Abstract

We present a design for a temperature-controlled sample shuttle for use in NMR measurements at variable magnetic field strength. Accurate temperature control was achieved using a mixture of water-ethylene glycol as a heat transfer fluid, reducing temperature gradients across the sample to < 0.05 °C and minimising convection. Using the sample shuttle, we show how the longitudinal (T1) and singlet order (TS) relaxation time constants were measured for two molecules capable of supporting long-lived states, with new record lifetimes observed at low field and above ambient temperatures.

Highlights

Many physical parameters important in NMR spectroscopy exhibit strong temperature and magnetic field dependencies which can be utilised to investigate underlying relaxation mechanisms and molecular dynamics
Apparatus for NMR dispersion measurements fall into two categories; fast field-cycling methods where the sample remains in a static position whilst the magnetic field is swept [1–3,12–16], and sample shuttle methods where the sample is physically transported between regions with different magnetic field strength [8,17–28]
We have demonstrated a design for a new temperaturecontrolled sample shuttle for NMR dispersion measurements

Summary

Introduction

Many physical parameters important in NMR spectroscopy exhibit strong temperature and magnetic field dependencies which can be utilised to investigate underlying relaxation mechanisms and molecular dynamics. NMR relaxometry measurements at variable magnetic field strength (dispersion measurements) are frequently used to study molecular dynamics in proteins, polymers and other complex systems [1–6]. Experiments at variable magnetic field strength are important for hyperpolarisation techniques, where they are used to determine relaxation rates and for polarisation transfer experiments [7–11]. Apparatus for NMR dispersion measurements fall into two categories; fast field-cycling methods where the sample remains in a static position whilst the magnetic field is swept [1–3,12–16], and sample shuttle methods where the sample is physically transported between regions with different magnetic field strength [8,17–28]. The low field environment in a sample shuttle system may either be a point within the stray field of the primary magnet, or a dedicated low field coil within a magnetic shield [25,28,29]

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