Enhancing 19F Benchtop NMR Spectroscopy by Combining para-Hydrogen Hyperpolarization and Multiplet Refocusing.

Benchtop NMR spectrometers provide a promising alternative to high-field NMR for applications that are limited by instrument size and/or cost. 19F benchtop NMR is attractive due to the larger chemical shift range of 19F relative to 1H and the lack of background signal in most applications. However, practical applications of benchtop 19F NMR are limited by its low sensitivity due to the relatively weak field strengths of benchtop NMR spectrometers. Here we present a sensitivity-enhancement strategy that combines SABRE (Signal Amplification By Reversible Exchange) hyperpolarization with the multiplet refocusing method SHARPER (Sensitive, Homogeneous, And Resolved PEaks in Real time). When applied to a range of fluoropyridines, SABRE-SHARPER achieves overall signal enhancements of up to 5700-fold through the combined effects of hyperpolarization and line-narrowing. This approach can be generalized to the analysis of mixtures through the use of a selective variant of the SHARPER sequence, selSHARPER. The ability of SABRE-selSHARPER to simultaneously boost sensitivity and discriminate between two components of a mixture is demonstrated, where selectivity is achieved through a combination of selective excitation and the choice of polarization transfer field during the SABRE step.

SHARPER-enhanced benchtop NMR: improving SNR by removing couplings and approaching natural linewidths.

We present a signal enhancement strategy for benchtop NMR that produces SNR increases on the order of 10 to 30 fold by collapsing the target resonance into an extremely narrow singlet. Importantly, the resultant signal is amenable to quantitative interpretation and therefore can be applied to analytical applications such as reaction monitoring.

In Situ SABRE Hyperpolarization with Earth's Field NMR Detection.

Hyperpolarization methods, which increase the sensitivity of nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI), have the potential to expand the range of applications of these powerful analytical techniques and to enable the use of smaller and cheaper devices. The signal amplification by reversible exchange (SABRE) method is of particular interest because it is relatively low-cost, straight-forward to implement, produces high-levels of renewable signal enhancement, and can be interfaced with low-cost and portable NMR detectors. In this work, we demonstrate an in situ approach to SABRE hyperpolarization that can be achieved using a simple, commercially-available Earth's field NMR detector to provide 1H polarization levels of up to 3.3%. This corresponds to a signal enhancement over the Earth's magnetic field by a factor of ε > 2 × 108. The key benefit of our approach is that it can be used to directly probe the polarization transfer process at the heart of the SABRE technique. In particular, we demonstrate the use of in situ hyperpolarization to observe the activation of the SABRE catalyst, the build-up of signal in the polarization transfer field (PTF), the dependence of the hyperpolarization level on the strength of the PTF, and the rate of decay of the hyperpolarization in the ultra-low-field regime.

High-Resolution Nuclear Magnetic Resonance Spectroscopy with Picomole Sensitivity by Hyperpolarization on a Chip.

We show that high-resolution NMR can reach picomole sensitivity for micromolar concentrations of analyte by combining parahydrogen-induced hyperpolarization (PHIP) with a high-sensitivity transmission line microdetector. The para-enriched hydrogen gas is introduced into solution by diffusion through a membrane integrated into a microfluidic chip. NMR microdetectors, operating with sample volumes of a few µL or less, benefit from a favorable scaling of mass sensitivity. However, the small volumes make it very difficult to detect species present at less than millimolar concentrations in microfluidic NMR systems. In view of overcoming this limitation, we implement PHIP on a microfluidic device with a 2.5 µL detection volume. Integrating the hydrogenation reaction into the chip minimizes polarization losses to spin-lattice relaxation, allowing the detection of picomoles of substance. This corresponds to a concentration limit of detection of better than 1µMs , unprecedented at this sample volume. The stability and sensitivity of the system allow quantitative characterization of the signal dependence on flow rates and other reaction parameters and permit homo- (1H-1H) and heteronuclear (1H-13C) 2D NMR experiments at natural 13C abundance.

Analysis of the Impacts of the Electrification of the Vehicle Fleet in the Electric Power System in Curitiba

ABSTRACT The Market share of electrical vehicles has been rising in the past few years and tends to rise even more. According to the International Energy Agency, an increase of 50% in the number of electrical vehicles is expected. Whilst that increase is beneficial from a greenhouse gases emissions drop point of view, that rise could, on the other hand, represent a major increase in the electrical power consumption. Besides, other problems such as harmonics and overloads could emerge from the massive connection of electrical vehicles to the electrical grid. Therefore, it is necessary to perform studies and simulations in order to estimate those problems and to mitigate the problems related to the inevitable expansion of the electric vehicle fleet in the near future. The present work intends to run simulations so as to identify the main effects of the electrification of the vehicular fleet in the city of Curitiba, as well as understand how the provision of ancillary services through the electrical vehicles can help in the process.