Benchtop NMR spectrometers are a promising technology for process monitoring applications due to their portability, affordability and low maintenance requirements. However, the moderate magnetic fields of benchtop NMR spectrometers (1 – 2 T) limit their sensitivity and chemical shift dispersion when compared to standard laboratory NMR (> 7 T). Hyperpolarisation is a promising approach to overcome the low sensitivity of benchtop NMR but poses additional challenges for quantification because the observed signal strength depends on the efficiency of the hyperpolarisation process as well as the concentration of the target species. Therefore, new strategies are need to transform hyperpolarised benchtop NMR into a suitable technique for quantitative process monitoring. Parahydrogen induced polarisation (PHIP) methods use the nuclear singlet spin isomer of molecular hydrogen, parahydrogen (p-H2), as the source of polarisation and a hydrogenation or reversible exchange reaction to generate NMR signal enhancements in solution. PHIP methods generate polarisation levels that are independent of the detection field strength and can be implemented with relatively simple instrumentation to generate signal enhancements of several orders of magnitude on a timescale of seconds. Therefore, they are very attractive for use with benchtop NMR spectrometers. Here we explore the use of hyperpolarised benchtop NMR to monitor reactivity involving parahydrogen. Perspectives for process monitoring more generally using the catalytic signal amplification by reversible exchange (SABRE) method coupled to benchtop NMR detection will also be discussed, with a focus on exploring the limits of detection and strategies for signal quantification.
Dr Meghan E. Halse is a Senior Lecturer in Chemistry at the University of York. She received her PhD in Physics from Victoria University of Wellington (NZ) in 2010, working under the supervision of Prof Paul Callaghan. Her PhD work focused on the development of instrumentation and methods for hyperpolarised ultra-low-field NMR and MRI. Following her PhD, she carried out post-doctoral research on simulating proton spin diffusion and developing homonuclear decoupling sequences for solid-state NMR at the Centre for very high field NMR (CRMN) at the CNRS in Lyon, France. In 2013 she moved to the University of York as a post-doctoral fellow in the Centre for Hyperpolarisation in Magnetic Resonance (CHyM), before taking up an independent Lectureship in Chemistry in 2015. Her current research focuses on the development of novel NMR and MRI methods using hyperpolarisation to improve sensitivity, with a particular focus on the development of low-field and portable NMR solutions for applications outside of the traditional laboratory environment.