Two fields are better than one – A multifunctional (semi)automated setup for quantitative measurements of parahydrogen-induced signal enhancement at low and high fields

Abstract

The rapid advancement of parahydrogen-induced hyperpolarization (PHIP) and its diverse array of applications highlights the critical need for enhanced signals in both ¹H NMR and heteronuclear NMR spectroscopy. Simultaneously, there is an increasing interest in utilizing benchtop NMR analysis across various laboratory settings. However, due to their lower magnetic fields, benchtop NMR spectrometers inherently produce weaker signal intensities. Here, PHIP is a well-established solution to this challenge. Consequently, we are expanding our cost-effective PHIP setup from a high-field NMR spectrometer (11.7 T) to include an additional benchtop NMR spectrometer (1.4 T), thereby enabling concurrent execution of PHIP experiments and measurements. Through the implementation of automated experimental protocols, we aim to minimize experiment time while increasing reproducibility. In this work, a non-isotope labelled propargyl alcohol sample is used at low concentrations to demonstrate our setup’s capabilities. It could be shown that single-scan PASADENA experiments can be run with comparable signal enhancements at the benchtop as well as the high-field spectrometer. At 1.4 T, fully automated PHIP pseudo-2D measurements will also be demonstrated. Additionally, two different field profiles for the spin-order transfer of p-H₂ to ¹³C at zero- to ultralow fields are elaborated upon. The setup facilitates the measurement of carbon signal enhancement of more than 2000 on the benchtop NMR spectrometer, employing a straightforward one-pulse, one-scan experiment.