Publications

Contact us

Spinsolve is a powerful, fully featured NMR Spectrometer and is used by a number of the worlds top NMR research groups.  Below is a selected list of journal articles where a Magritek Spinsolve Benchtop NMR spectrometer has been used in the published research. Spinsolve is being used for Research in topics such as online Reaction Monitoring,  Hyperpolarisation, Ultrafast 2D NMR, Residual Dipolar Couplings and Process Control.

A short abstract for each paper is included below, along with a hyperlink to more detailed information about each the papers.

 

1. Towards dial-a-molecule by integrating continuous flow, analytics and self-optimisation

Victor Sans, Leroy Cronin, Chemical Society Reviews, (2016), 45, 2032-2043 DOI: 10.1039/C5CS00793C

The employment of continuous-flow platforms for synthetic chemistry is becoming increasingly popular in research and industrial environments. Integrating analytics in-line enables obtaining a large amount of information in real-time about the reaction progress, catalytic activity and stability, etc. Furthermore, it is possible to influence the reaction progress and selectivity via manual or automated feedback optimisation, thus constituting a dial-a-molecule approach employing digital synthesis. This contribution gives an overview of the most significant contributions in the field to date.

 

2. Process control with compact NMR

Klas Meyer, Simon Kern, Nicolai Zientek, Gisela Guthausen, Michael Maiwald, Trends in Analytical Chemistry, (2016) DOI: 10.1016/j.trac.2016.03.016

Compact nuclear magnetic resonance (NMR) instruments make NMR spectroscopy and relaxometry accessible in industrial and harsh environments for reaction and process control. An increasing number of applications are reported. To build an interdisciplinary bridge between “process control” and “compact NMR”, we give a short overview on current developments in the field of process engineering such as modern process design, integrated processes, intensified processes along with requirements to process control, model based control, or soft sensing. Finally, robust field integration of NMR systems into processes environments, facing explosion protection or integration into process control systems, are briefly discussed.

 

3. Paramagnetic fluorinated nanoemulsions for sensitive cellular fluorine-19 magnetic resonance imaging

Alexander A. Kislukhin, Hongyan Xu, Stephen R. Adams, Kazim H. Narsinh, Roger Y. Tsien, Eric T. Ahrens, Nature Materials, (2016),15, 662–668 DOI: 10.1038/NMAT4585

Fluorine-19 magnetic resonance imaging (19F MRI) probes enable quantitative in vivo detection of cell therapies and inflammatory cells. Here, we describe the formulation of perfluorocarbon-based nanoemulsions with improved sensitivity for cellular MRI. Reduction of the 19F spin–lattice relaxation time (T1) enables rapid imaging and an improved signal-to-noise ratio, thereby improving cell detection sensitivity. We synthesized metal-binding β-diketones conjugated to linear perfluoropolyether (PFPE), formulated these fluorinated ligands as aqueous nanoemulsions, and then metallated them with various transition and lanthanide ions in the fluorous phase. Iron(III) tris-β-diketonate (‘FETRIS) nanoemulsions with PFPE have low cytotoxicity (<20%) and superior MRI properties. Moreover, the 19F T1 can readily be reduced by an order of magnitude and tuned by stoichiometric modulation of the iron concentration. The resulting 19F MRI detection sensitivity is enhanced by three- to fivefold over previously used tracers at 11.7T, and is predicted to increase by at least eightfold at the clinical field strength of 3T.

 

4. Ultrafast 2D NMR on a benchtop spectrometer: Applications and perspectives

Boris Gouilleux, Benoît Charrier, Serge Akoka, François-Xavier Felpin, Mireia Rodriguez-Zubiri, Patrick Giraudeau, Trends in Analytical Chemistry, (2016) DOI: 10.1016/j.trac.2016.01.014

Benchtop NMR spectrometers are associated with significant resolution losses, as peak overlaps become ubiquitous at low field. 2D spectroscopy offers an appealing solution to this issue. However 2D NMR is associated with long experimental times which are ill-suited for high-throughput applications such as real-time reaction monitoring or rapid screening. The first implementation of ultrafast (UF) 2D NMR on a benchtop spectrometer –including B0 gradients– was recently reported, making it possible to record 2D spectra in a single –or at most a few– scans. In the present review, we investigate the analytical performance of UF 2D NMR at low field (43 MHz) and its application potential in two complementary research fields: real-time reaction monitoring and rapid screening. UF 2D spectroscopy at low field appears to be a powerful complement to existing analytical methods, and paves the way towards a number of developments in the field of spatially-encoded NMR at low field.

 

5. Introduction to compact NMR: A review of methods

Bernhard Blümich, Trends in Analytical Chemistry, (2016)  DOI: 10.1016/j.trac.2015.12.012

NMR spectroscopy with compact instruments opens new perspectives for the use of NMR. While the field strength of compact instruments is low, they potentially match today’s high-field instruments in methodical diversity, although by default they are operated in non-expert mode with a mouse click. Because size and price are low, they open new opportunities for the use of NMR spectroscopy. One is product and quality control and another is real-time reaction monitoring in the academic and industrial research laboratory on the workbench by observing nuclei such as 1H, 13C, 31P, 19F, 7Li and 11B. With compact NMR spectrometers, not only standard one-dimensional experiments can be executed to retrieve chemical information but also the two-dimensional experiments such as HSQC, HMBC, HETCOR and COSY. The state of the art and progress in compact NMR spectroscopy is reviewed concerning 1D and 2D spectroscopy along with their use in product control and reaction monitoring.

 

6. NMR spectroscopy with compact instruments

Kawarpal Singh, Bernhard Blümich, Trends in Analytical Chemistry, (2016) DOI: 10.1016/j.trac.2016.02.014

Recent progress in magnet design has led to compact permanent magnets capable of resolving the chemical shift, so that small NMR spectrometers are now available, which can measure multi-nuclear and multi-dimensional NMR spectra on the workbench of the chemical laboratory. Although not as powerful as today’s high-field spectrometers, their performance by far exceeds that of spectrometers from former times when high-field instruments were not available. Moreover, they are compact and robust, enabling the use of NMR in studies currently constrained by the demands posed by operating large cryogenically cooled magnets. The current state-of-the-art of compact low-field NMR instruments is reviewed from a methodological point of view making reference to basic NMR theory where needed to characterize their performance.

 

7. Hyperpolarization of Nitrogen-15 Schiff Bases by Reversible Exchange Catalysis with para-Hydrogen

Angus W. J. Logan, Thomas Theis, Johannes F. P. Colell, Warren S. Warren, Steven J. Malcolmson, Chemistry A European Journal, (2016) DOI: 10.1002/chem.201602393

NMR with thermal polarization requires relatively concentrated samples, particularly for nuclei with low abundance and low gyromagnetic ratios, such as 15N. We expand the substrate scope of SABRE, a recently introduced hyperpolarization method, to allow access to 15N-enriched Schiff bases. These substrates show fractional 15N polarization levels of up to 2 % while having only minimal 1H enhancements.

 

8. Real-time reaction monitoring by ultrafast 2D NMR on a benchtop spectrometer

Boris Gouilleux, Benoît Charrier, Ernesto Danieli, Jean-Nicolas Dumez, Serge Akoka, François-Xavier Felpin, Mireia Rodriguez-Zubiria, Patrick Giraudeau, Analyst, (2015),140, 7854-7858 DOI: 10.1039/C5AN01998B

Reaction monitoring is widely used to follow chemical processes in a broad range of application fields. Recently, the development of robust benchtop NMR spectrometers has brought NMR under the fume hood, making it possible to monitor chemical reactions in a safe and accessible environment. However, these low-field NMR approaches suffer from limited resolution leading to strong peak overlaps, which can limit their application range. Here, we propose an approach capable of recording ultrafast 2D NMR spectra on a compact spectrometer and of following in real time reactions in the synthetic chemistry laboratory. This approach – whose potential is shown here on a Heck–Matsuda reaction – is highly versatile; the duration of the measurement can be optimized to follow reactions whose time scale ranges from between a few tens of seconds to a few hours. It makes it possible to monitor complex reactions in non-deuterated solvents, and to confirm in real time the molecular structure of the compounds involved in the reaction while giving access to relevant kinetic parameters.

 

9. On-Line Monitoring of Chemical Reactions by using Benchtop Nuclear Magnetic Resonance Spectroscopy

E. Danieli, J. Perlo, A. L. L. Duchateau, G. K. M. Verzijl, V. M. Litvinov, B. Blümich, F. Casanova, ChemPhysChem, (2014),14 (14), 3060–3066 DOI: 10.1002/cphc.201402049

Real-time nuclear magnetic resonance (NMR) spectroscopy measurements carried out with a bench-top system installed next to the reactor inside the fume hood of the chemistry laboratory are presented. To test the system for on-line monitoring, a transfer hydrogenation reaction was studied by continuously pumping the reaction mixture from the reactor to the magnet and back in a closed loop. In addition to improving the time resolution provided by standard sampling methods, the use of such a flow setup eliminates the need for sample preparation. Owing to the progress in terms of field homogeneity and sensitivity now available with compact NMR spectrometers, small molecules dissolved at concentrations on the order of 1 mmol L−1 can be characterized in single-scan measurements with 1 Hz resolution. Owing to the reduced field strength of compact low-field systems compared to that of conventional high-field magnets, the overlap in the spectrum of different NMR signals is a typical situation. The data processing required to obtain concentrations in the presence of signal overlap are discussed in detail, methods such as plain integration and line-fitting approaches are compared, and the accuracy of each method is determined. The kinetic rates measured for different catalytic concentrations show good agreement with those obtained with gas chromatography as a reference analytical method. Finally, as the measurements are performed under continuous flow conditions, the experimental setup and the flow parameters are optimized to maximize time resolution and signal-to-noise ratio.

 

10. Simultaneous 19F–1H medium resolution NMR spectroscopy for online reaction monitoring

Nicolai Zientek, Clément Laurain, Klas Meyer, Matthias Kraume, Gisela Guthausen, Michael Maiwald, Journal of Magnetic Resonance, (2014), 249, 53–62 DOI: 10.1016/j.jmr.2014.10.007

Medium resolution nuclear magnetic resonance (MR-NMR) spectroscopy is currently a fast developing field, which has an enormous potential to become an important analytical tool for reaction monitoring, in hyphenated techniques, and for systematic investigations of complex mixtures. The recent developments of innovative MR-NMR spectrometers are therefore remarkable due to their possible applications in quality control, education, and process monitoring. MR-NMR spectroscopy can beneficially be applied for fast, non-invasive, and volume integrating analyses under rough environmental conditions.

 

11. Liquid-liquid equilibrium in binary and ternary mixtures containing formaldehyde, water, methanol, methylal, and poly(oxymethylene) dimethyl ethers

Niklas Schmitz, Anne Friebel, Erik von Harbou, Jakob Burger, Hans Hasse, Fluid Phase Equilibria, (2016), 425, 127-135, DOI: 10.1016/j.fluid.2016.05.017

Poly(oxymethylene) dimethyl ethers (OME) are an interesting class of oxygenated fuel components and solvents for the absorption of carbon dioxide. The chemical structure of OMEn is H3C–O–(CH2O)n–CH3 with n ≥ 2 and the IUPAC names are methoxy(methoxymethoxy)methane (n = 2), 2,4,6,8-tetraoxanonane (n = 3), and 2,4,6,8,10-pentaoxaundecane (n = 4). This work studies the liquid-liquid equilibrium (LLE) in the binary systems (water + methylal), (water + OME2), (water + OME3), and (water + OME4) and the ternary systems (water + methanol + OME2), (water + methanol + OME3), (formaldehyde + water + OME2), (formaldehyde + water + OME3), and (water + methylal + OME2) in the temperature range 280 K – 340 K. The systems were studied by gas chromatographic- and titrimetric analysis of samples that were drawn from the coexisting liquid phases, as well by in situ analysis with a medium-field NMR spectrometer. The LLE was modeled by extending a UNIFAC-based activity coefficient model of the system (formaldehyde + water + methanol + methylal) from the literature. One new structural group is introduced to represent the OME.

 

12. Automated data evaluation and modelling of simultaneous 19F–1H medium-resolution NMR spectra for online reaction monitoring

Nicolai Zientek, Clément Laurain, Klas Meyer, Andrea Paul, Dirk Engel, Gisela Guthausen, Matthias Kraumee, Michael Maiwald, Magnetic Resonance in Chemistry, (2016), 54 (6), 513–520, DOI: 10.1002/mrc.4216

Medium-resolution nuclear magnetic resonance spectroscopy (MR-NMR) currently develops to an important analytical tool for both quality control and process monitoring. In contrast to high-resolution online NMR (HR-NMR), MR-NMR can be operated under rough environmental conditions. A continuous re-circulating stream of reaction mixture from the reaction vessel to the NMR spectrometer enables a non-invasive, volume integrating online analysis of reactants and products. Here, we investigate the esterification of 2,2,2-trifluoroethanol with acetic acid to 2,2,2-trifluoroethyl acetate both by 1H HR-NMR (500 MHz) and 1H and 19F MR-NMR (43 MHz) as a model system.

 

13. Compact NMR spectroscopy for real-time monitoring of a biodiesel production

M.H.M. Killner, Y. Garro Linck, E. Danieli, J.J.R. Rohwedder, B. Blümich, Fuel, (2015), 139, 240-247, DOI: 10.1016/j.fuel.2014.08.050

The use of biodiesel shows innumerous advantages compared to fossil fuels, since biodiesel is a biodegradable and non-toxic fuel. Nowadays, most of the biodiesel commercialized in the world is produced by the transesterification reaction of vegetable oils with methanol and basic catalysis. Understanding the reaction kinetics and controlling its optimum progress for improving the quality of the final product and to reduce production costs is of paramount importance. The present work explores compact 1H NMR spectroscopy to follow the course of the transesterification reaction in real time. For this purpose the magnet is integrated into a flow setup which allows one to transport the neat solution from the reactor into the measurement zone and back again into the reactor. A multivariate calibration model applying Partial Least Squares regression was built to analyze the measured data and to obtain information about the biodiesel conversion ratio with errors on the order of 1%.

 

14. Differentiation of enantiomers by 2D NMR spectroscopy at 1T using residual dipolar couplings

Martin R. M. Koos, Ernesto Danieli, Federico Casanova, Bernhard Blümich, Burkhard Luy, Magnetic Resonance in Chemistry, (2016), 54 (6), 527-530, DOI: 10.1002/mrc.4222

Differentiating enantiomers using 2D bench-top NMR spectroscopy. Spectrometers working with permanent magnets at 1 T field strength allow the acquisition of 2D data sets. In conjunction with previously reported chiral alignment media, this setup allows the measurement of enantiomeric excess via residual dipolar couplings in stretched gelatine as a result of the reduced line width obtained by 2D J-resolved spectroscopy.

 

15. Online Monitoring of Fermentation Processes Via Non-Invasive Low-Field NMR

Dirk Kreyenschulte, Eva Paciok, Lars Regestein, Bernhard Blümich, Jochen Büchs, Biotechnology and Bioengineering, (2015), 112 (9), 1810-1821, DOI: 10.1002/bit.25599

For the development of biotechnological processes in academia as well as in industry new techniques are required which enable online monitoring for process characterization and control. Nuclear magnetic resonance (NMR) spectroscopy is a promising analytical tool, which has already found broad applications in offline process analysis. The use of online monitoring, however, is oftentimes constrained by high complexity of custom-made NMR bioreactors and considerable costs for high-field NMR instruments (>US$200,000). Therefore, low-field 1H NMR was investigated in this study in a bypass system for real-time observation of fermentation processes. The new technique was validated with two microbial systems. Both applications clearly demonstrate that the investigated technique is well suited for reaction monitoring in opaque media while at the same time it is highly robust and chemically specific. It can thus be concluded that low-field NMR spectroscopy has a great potential for non-invasive online monitoring of biotechnological processes at the research and practical industrial scales

 

16. A Self Optimizing Synthetic Organic Reactor System Using Real-time In-line NMR spectroscopy

Victor Sans, Luzian Porwol, Vincenza Dragone, Leroy Cronin, Chemical Science, (2015), 6, 1258-1264, DOI: 10.1039/C4SC03075C

A configurable platform for synthetic chemistry incorporating an in-line benchtop NMR that is capable of monitoring and controlling organic reactions in real-time is presented. The platform is controlled via a modular LabView software control system for the hardware, NMR, data analysis and feedback optimization. Using this platform we report the real-time advanced structural characterization of reaction mixtures, including 19F, 13C, DEPT, 2D NMR spectroscopy (COSY, HSQC and 19F-COSY) for the first time. Finally, the potential of this technique is demonstrated through the optimization of a catalytic organic reaction in real-time, showing its applicability to self-optimizing systems using criteria such as stereoselectivity, multi-nuclear measurements or 2D correlations.