Benchtop nuclear magnetic resonance spectrometer

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A Benchtop nuclear magnetic resonance spectrometer (Benchtop NMR spectrometer) refers to a Fourier transform nuclear magnetic resonance (FT-NMR) spectrometer that is significantly more compact and portable than the conventional equivalents, such that it is portable and can reside on a laboratory benchtop. This convenience comes from using permanent magnets, which have a lower magnetic field and decreased sensitivity compared to the much larger and more expensive cryogen cooled superconducting NMR magnets. Instead of requiring dedicated infrastructure, rooms and extensive installations these benchtop instruments can be placed directly on the bench in a lab and moved as necessary (e.g., to the fumehood). These spectrometers offer improved workflow, even for novice users, as they are simpler and easy to use. They differ from relaxometers in that they can be used to measure high resolution NMR spectra and are not limited to the determination of relaxation or diffusion parameters (e.g., T1, T2 and D).

Contents

Magnet development

The first generation of NMR spectrometers used large Electromagnets weighing hundreds of kilograms or more. Slightly smaller permanent magnet systems were developed in the 1960s-70s at proton resonance frequencies of 60 and 90 MHz and were widely used for chemical analysis using continuous wave methods, but these permanent magnets still weighed hundreds of kilograms and could not be placed on a benchtop. Superconducting magnets were developed to achieve stronger magnetic fields for higher resolution and increased sensitivity. However, these superconducting magnets are expensive, large, and require specialized building facilities. [1] In addition, the cryogens needed for the superconductors are hazardous, and represent an ongoing maintenance cost. [2] [3] [ unreliable source? ] As a result, these instruments are usually installed in dedicated NMR rooms or facilities for use by multiple research groups.

Since the early 2000s there has been a renaissance in permanent-magnet technology and design, [4] with advances sufficient to allow development of much smaller NMR instruments with useful resolution and sensitivity for education, research and industrial applications. [5] Samarium–cobalt and neodymium hard ferromagnets have reduced the size of NMR permanent magnets, and fields up to 2.9 T have been reached, corresponding to a 125 MHz proton Larmor frequency. These designs, which operate with magnet temperatures from room temperature to 60 °C, allow instruments to be made small enough to fit on a lab bench, and are safe to operate in a typical lab environment. They require only single phase local power, and with UPS systems can be made portable and can perform NMR analyses at different points in a manufacturing area.

Disadvantages of Small-Size Magnets and Methods to Overcome them

One of the biggest disadvantages of low-field (0.3-1.5T) NMR spectrometers is the temperature dependence of the permanent magnets used to produce the main magnetic field. For small magnets there was a concern that the intensity of external magnetic fields may adversely affect the main field, however the use of magnetic shielding materials inside the spectrometer eliminates this problem. The currently available spectrometers are easily moved from one location to another, including some that are mounted on portable trolleys with continuous power supplies. [6] Another related difficulty is that currently available spectrometers do not support elevated sample temperatures which may be required for some in-situ measurements in chemical reactions.

A recent paper suggests that a special experimental setup, with two or more coils and synchronous oscillators, may help overcome this problem [7] and allow it to work with unstable magnetic fields and with affordable oscillators.

NMR spectra acquired at low field suffer from less signal dispersion, which also leads to more complicated spectra with overlapping signals and higher order effects. [8] The complete interpretation of such spectra requires computational quantum mechanical spectral analysis, [9] for 1H-1D NMR spectra also known as HiFSA. [10]

Applications

NMR spectroscopy can be used for chemical analysis, [11] [12] reaction monitoring, [13] and quality assurance/quality control experiments. Higher-field instruments enable unparalleled resolution for structure determination, particularly for complex molecules. Cheaper, more robust, and more versatile medium and low field instruments have sufficient sensitivity and resolution for reaction monitoring and QA/QC analyses. [1] As such permanent magnet technology offers the potential to extend the accessibility and availability of NMR to institutions that do not have access to super-conducting spectrometers (e.g., beginning undergraduates [14] or small-businesses).

Many automated applications utilizing multivariate statistical analyses (chemometrics) approaches to derive structure-property and chemical and physical property correlations between 60 MHz 1H NMR spectra and primary analysis data particularly for petroleum and petrochemical process control applications have been developed over the past decade. [15] [16]

Available Benchtop NMR Spectrometers

Development of this new class of spectrometers began in the mid-2000s leaving this one of the last molecular spectroscopy techniques to be made available for the benchtop.

Spinsolve

New Zealand- and Germany-based Magritek's Spinsolve instrument, operating at 90 MHz, [17] 80 MHz, [18] and 60 MHz, [19] offers very good sensitivity and resolution less than 0.4 Hz and weighs 115 kg, 73 kg, and 60 kg respectively. The ULTRA model [20] has an even higher resolution of 0.2 Hz with a lineshape of 0.2 Hz/ 6 Hz/ 12 Hz comparable to high field NMR specifications. 1H Proton, 19F Fluorine, 13C Carbon, 31P Phosphorus and other X-nuclei such as 7Li, 23Na, 29Si and others can be measured. Multiple X nuclei can be included on a single spectrometer, without sensitivity loss, using the Multi X option. [21] A wide range of NMR spectra can be acquired including 1D, 1D with decoupling, solvent suppression, DEPT, T1, T2 and 2D HETCOR, HMBC, HMQC, COSY and JRES spectra. Pulsed field gradients for spectroscopy are included, and optional Diffusion pulsed field gradients [22] can also be added. The magnet is stabilised with an external lock, which means it does not require the use of deuterated solvents. An online reaction monitoring accessory using a flow cell, and an autosampler are available. Samples are measured using standard 5 mm NMR tubes and the spectrometer is controlled through an external computer where standard NMR data collection and processing takes place.

picoSpin

In 2009, picoSpin LLC, based in Boulder, Colorado, launched the first benchtop NMR spectrometer with the picoSpin 45. A small (7 x 5.75 x 11.5”) 45 MHz spectrometer with good resolution (< 1.8 Hz) and mid-to-low-range sensitivity that weighs 4.76 kg (10.5 lbs) and can acquire a 1D 1H or 19F spectra. PicoSpin was acquired by Thermo Fisher Scientific in December 2012, and subsequently renamed the product Thermo Scientific picoSpin 45. [23] Instead of the traditional static 5 mm NMR tubes, the picoSpin 45 spectrometer uses a flow-through system that requires sample injection into an 0.4 mm ID PTFE and quartz capillary. [24] Deuterated solvents are optional due to the presence of a software lock. It needs only a web browser on any external computer or mobile device for control as the spectrometer has a built-in web server board; no installed software on a dedicated PC is required. In August 2013 a second version was introduced, the Thermo Scientific picoSpin 80, that operates at 82 MHz with a resolution of 1.2 Hz and ten times the sensitivity of the original picoSpin 45.

Nanalysis

Calgary, AB, Canada based Nanalysis Corp offers two benchtop NMR platforms: 60 and 100 MHz, which is 1.4 T and 2.35 T, respectively. The spectrometers are in an all-in-one enclosure (magnet, electronics and touchscreen computer) making them easier to site but all systems can be controlled locally or remotely by an external computer as preferred by the user. The 60 MHz is the smallest 60 MHz available on the market, weighing about 25 kg, and the 100 MHz, just under 100 kg.

Both platforms come in an ‘e’ model, which can acquire 1H/19F or in a ‘PRO’ model that observes 1H/19F/X (where X is defined by the customer but is most commonly 7Li, 11B, 13C, 31P). Depending on the model of instrument, it can perform 1D 1H, 13C{1H}, 19F, 31P, 31P{1H}, COSY, JRES, DEPT, APT, HSQC, HSQC-ME, HMBC, T1 and T2 experiments. The spectrometers use standard 5mm NMR tubes and are compatible with most third party NMR software suites.

Nanalysis acquired RS2D in 2020, expanding their magnetic resonance technology portfolio to include their superior cameleon4 technology, NMR consoles , preclinical MRI, and MR product lines. In 2021 Nanalysis also acquired the New York based software company, One Moon Scientific, to both offer routine, high-performance data processing and expand the analysis of NMR data including machine learning, database construction and search algorithms.

X-Pulse / Pulsar

In 2019, Oxford Instruments launched a new 60 MHz spectrometer called X-Pulse. [25] This instrument is a significant improvement on the previous Pulsar system, launched in 2013. X-Pulse has the highest, as standard, resolution (<0.35 Hz / 10 Hz) of the currently available benchtop, cryogen-free NMR analysers. It incorporates a 60 MHz rare-earth permanent magnet. X-Pulse is the only benchtop NMR system to offer a full broadband X channel for the allowing the measurement of 1H,19F, 13C, 31P, 7Li, 29Si, 11B and 23Na on a single probe. A large range of 1D and 2D measurements can be performed on all nuclei, 1D spectra, T1, T2, HETCOR, COSY, HSQC, HMBC, JRES, and many others including solvent suppression and selective excitation. X-Pulse also has options for flow NMR and a variable temperature probe allowing the measurement of samples in NMR tubes at temperatures from 20 °C to 60 °C. The magnet and spectrometer are in two separate boxes with the magnet weighing 149 kg [26] and the electronics weighing 22 kg. X-Pulse requires a standard mains electrical supply and uses standard 5mm NMR tubes. Instrument control comes from the SpinFlow workflow package, while the processing and manipulation of data is achieved using third-party NMR software suites. Pulsar instruments were discontinued in 2019 following the launch of X-Pulse.

Bruker

In 2019, Bruker, a long time manufacturer and market leader of high performance NMR machines, introduced a Benchtop NMR, Fourier 80 FT-NMR. The machine uses permanent magnets, and operates using Bruker standard software (a full futured TopSpin 4 software for Windows and Linux; as well Python based API from Windows and Linux; and a simplified app called GoScan). Machine can be configured for 1H and 13C spectra (possibly more by a custom order) in 1D and 2D modes, and operates at 80 MHz (1.88 T). The machine weighs about 93 kg and consumes less than 300W when operating. [27]

Q Magnetics

In late 2021, Q Magnetics introduced the QM-125, a 125 MHz (2.9 T) 1H benchtop NMR spectrometer with resolution better than 0.5 Hz. [28] The instrument is contained in a single enclosure with a mass of 28 kg, and is connected to a controlling computer by a USB interface. The QM-125 spectrometer does not require the user to first transfer their sample to an NMR tube. It may be used in two ways:  a walkup mode where a sample is drawn from a source with a syringe and then injected into the spectrometer; and an automated or hyphenated mode, where the sample is delivered to the RF coil by flow from another instrument. Other features that support automated and hyphenated applications are stable shim, open-source Python control software, and front-panel fluid connections. Power consumption of less than 50 W and relatively low cost support integration into vertical and dedicated applications.

Related Research Articles

In nuclear magnetic resonance (NMR) spectroscopy, the chemical shift is the resonant frequency of an atomic nucleus relative to a standard in a magnetic field. Often the position and number of chemical shifts are diagnostic of the structure of a molecule. Chemical shifts are also used to describe signals in other forms of spectroscopy such as photoemission spectroscopy.

<span class="mw-page-title-main">Nuclear magnetic resonance spectroscopy</span> Laboratory technique

Nuclear magnetic resonance spectroscopy, most commonly known as NMR spectroscopy or magnetic resonance spectroscopy (MRS), is a spectroscopic technique based on re-orientation of atomic nuclei with non-zero nuclear spins in an external magnetic field. This re-orientation occurs with absorption of electromagnetic radiation in the radio frequency region from roughly 4 to 900 MHz, which depends on the isotopic nature of the nucleus and increased proportionally to the strength of the external magnetic field. Notably, the resonance frequency of each NMR-active nucleus depends on its chemical environment. As a result, NMR spectra provide information about individual functional groups present in the sample, as well as about connections between nearby nuclei in the same molecule. As the NMR spectra are unique or highly characteristic to individual compounds and functional groups, NMR spectroscopy is one of the most important methods to identify molecular structures, particularly of organic compounds.

<span class="mw-page-title-main">Electron paramagnetic resonance</span> Technique to study materials that have unpaired electrons

Electron paramagnetic resonance (EPR) or electron spin resonance (ESR) spectroscopy is a method for studying materials that have unpaired electrons. The basic concepts of EPR are analogous to those of nuclear magnetic resonance (NMR), but the spins excited are those of the electrons instead of the atomic nuclei. EPR spectroscopy is particularly useful for studying metal complexes and organic radicals. EPR was first observed in Kazan State University by Soviet physicist Yevgeny Zavoisky in 1944, and was developed independently at the same time by Brebis Bleaney at the University of Oxford.

<span class="mw-page-title-main">Solid-state nuclear magnetic resonance</span>

Solid-state NMR (ssNMR) spectroscopy is a technique for characterizing atomic level structure in solid materials e.g. powders, single crystals and amorphous samples and tissues using nuclear magnetic resonance (NMR) spectroscopy. The anisotropic part of many spin interactions are present in solid-state NMR, unlike in solution-state NMR where rapid tumbling motion averages out many of the spin interactions. As a result, solid-state NMR spectra are characterised by larger linewidths than in solution state NMR, which can be utilized to give quantitative information on the molecular structure, conformation and dynamics of the material. Solid-state NMR is often combined with magic angle spinning to remove anisotropic interactions and improve the resolution as well as the sensitivity of the technique.

Carbon-13 (C13) nuclear magnetic resonance is the application of nuclear magnetic resonance (NMR) spectroscopy to carbon. It is analogous to proton NMR and allows the identification of carbon atoms in an organic molecule just as proton NMR identifies hydrogen atoms. 13C NMR detects only the 13
C
 isotope. The main carbon isotope, 12
C
 does not produce an NMR signal. Although ca. 1 mln. times less sensitive than 1H NMR spectroscopy, 13C NMR spectroscopy is widely used for characterizing organic and organometallic compounds, primarily because 1H-decoupled 13C-NMR spectra are more simple, have a greater sensitivity to differences in the chemical structure, and, thus, are better suited for identifying molecules in complex mixtures. At the same time, such spectra lack quantitative information about the atomic ratios of different types of carbon nuclei, because nuclear Overhauser effect used in 1H-decoupled 13C-NMR spectroscopy enhances the signals from carbon atoms with a larger number of hydrogen atoms attached to them more than from carbon atoms with a smaller number of H's, and because full relaxation of 13C nuclei is usually not attained, and the nuclei with shorter relaxation times produce more intense signals.

Two-dimensional nuclear magnetic resonance spectroscopy is a set of nuclear magnetic resonance spectroscopy (NMR) methods which give data plotted in a space defined by two frequency axes rather than one. Types of 2D NMR include correlation spectroscopy (COSY), J-spectroscopy, exchange spectroscopy (EXSY), and nuclear Overhauser effect spectroscopy (NOESY). Two-dimensional NMR spectra provide more information about a molecule than one-dimensional NMR spectra and are especially useful in determining the structure of a molecule, particularly for molecules that are too complicated to work with using one-dimensional NMR.

In nuclear chemistry and nuclear physics, J-couplings are mediated through chemical bonds connecting two spins. It is an indirect interaction between two nuclear spins that arises from hyperfine interactions between the nuclei and local electrons. In NMR spectroscopy, J-coupling contains information about relative bond distances and angles. Most importantly, J-coupling provides information on the connectivity of chemical bonds. It is responsible for the often complex splitting of resonance lines in the NMR spectra of fairly simple molecules.

Nuclear magnetic resonance (NMR) in the geomagnetic field is conventionally referred to as Earth's field NMR (EFNMR). EFNMR is a special case of low field NMR.

In vivo magnetic resonance spectroscopy (MRS) is a specialized technique associated with magnetic resonance imaging (MRI).

Carbon satellites in physics and spectroscopy, are small peaks that can be seen shouldering the main peaks in the nuclear magnetic resonance (NMR) spectrum. These peaks can occur in the NMR spectrum of any NMR active atom where those atoms adjoin a carbon atom. However, Carbon satellites are most often encountered in proton NMR.

The Spectral Database for Organic Compounds (SDBS) is a free online searchable database hosted by the National Institute of Advanced Industrial Science and Technology (AIST) in Japan, that contains spectral data for ca 34,000 organic molecules. The database is available in English and in Japanese and it includes six types of spectra: laser Raman spectra, electron ionization mass spectra (EI-MS), Fourier-transform infrared (FT-IR) spectra, 1H nuclear magnetic resonance (1H-NMR) spectra, 13C nuclear magnetic resonance (13C-NMR) spectra and electron paramagnetic resonance (EPR) spectra. The construction of the database started in 1982. Most of the spectra were acquired and recorded in AIST and some of the collections are still being updated. Since 1997, the database can be accessed free of charge, but its use requires agreeing to a disclaimer; the total accumulated number of times accessed reached 550 million by the end of January, 2015.

A nuclear magnetic resonance spectra database is an electronic repository of information concerning Nuclear magnetic resonance (NMR) spectra. Such repositories can be downloaded as self-contained data sets or used online. The form in which the data is stored varies, ranging from line lists that can be graphically displayed to raw free induction decay (FID) data. Data is usually annotated in a way that correlates the spectral data with the related molecular structure.

<span class="mw-page-title-main">Phosphorus-31 nuclear magnetic resonance</span> Spectroscopy technique for molecules containing phosphorus

Phosphorus-31 NMR spectroscopy is an analytical chemistry technique that uses nuclear magnetic resonance (NMR) to study chemical compounds that contain phosphorus. Phosphorus is commonly found in organic compounds and coordination complexes, making it useful to measure 31- NMR spectra routinely. Solution 31P-NMR is one of the more routine NMR techniques because 31P has an isotopic abundance of 100% and a relatively high gyromagnetic ratio. The 31P nucleus also has a spin of 1/2, making spectra relatively easy to interpret. The only other highly sensitive NMR-active nuclei spin 1/2 that are monoisotopic are 1H and 19F.

<span class="mw-page-title-main">Fluorine-19 nuclear magnetic resonance spectroscopy</span> Analytical technique

Fluorine-19 nuclear magnetic resonance spectroscopy is an analytical technique used to detect and identify fluorine-containing compounds. 19F is an important nucleus for NMR spectroscopy because of its receptivity and large chemical shift dispersion, which is greater than that for proton nuclear magnetic resonance spectroscopy.

Carbohydrate NMR spectroscopy is the application of nuclear magnetic resonance (NMR) spectroscopy to structural and conformational analysis of carbohydrates. This method allows the scientists to elucidate structure of monosaccharides, oligosaccharides, polysaccharides, glycoconjugates and other carbohydrate derivatives from synthetic and natural sources. Among structural properties that could be determined by NMR are primary structure, saccharide conformation, stoichiometry of substituents, and ratio of individual saccharides in a mixture. Modern high field NMR instruments used for carbohydrate samples, typically 500 MHz or higher, are able to run a suite of 1D, 2D, and 3D experiments to determine a structure of carbohydrate compounds.

<span class="mw-page-title-main">Nuclear magnetic resonance</span> Spectroscopic technique based on change of nuclear spin state

Nuclear magnetic resonance (NMR) is a physical phenomenon in which nuclei in a strong constant magnetic field are perturbed by a weak oscillating magnetic field and respond by producing an electromagnetic signal with a frequency characteristic of the magnetic field at the nucleus. This process occurs near resonance, when the oscillation frequency matches the intrinsic frequency of the nuclei, which depends on the strength of the static magnetic field, the chemical environment, and the magnetic properties of the isotope involved; in practical applications with static magnetic fields up to ca. 20 tesla, the frequency is similar to VHF and UHF television broadcasts (60–1000 MHz). NMR results from specific magnetic properties of certain atomic nuclei. High-resolution nuclear magnetic resonance spectroscopy is widely used to determine the structure of organic molecules in solution and study molecular physics and crystals as well as non-crystalline materials. NMR is also routinely used in advanced medical imaging techniques, such as in magnetic resonance imaging (MRI). The original application of NMR to condensed matter physics is nowadays mostly devoted to strongly correlated electron systems. It reveals large many-body couplings by fast broadband detection and should not be confused with solid state NMR, which aims at removing the effect of the same couplings by Magic Angle Spinning techniques.

Nucleic acid NMR is the use of nuclear magnetic resonance spectroscopy to obtain information about the structure and dynamics of nucleic acid molecules, such as DNA or RNA. It is useful for molecules of up to 100 nucleotides, and as of 2003, nearly half of all known RNA structures had been determined by NMR spectroscopy.

<span class="mw-page-title-main">Paramagnetic nuclear magnetic resonance spectroscopy</span> Spectroscopy of paramagnetic compounds via NMR

Paramagnetic nuclear magnetic resonance spectroscopy refers to nuclear magnetic resonance (NMR) spectroscopy of paramagnetic compounds. Although most NMR measurements are conducted on diamagnetic compounds, paramagnetic samples are also amenable to analysis and give rise to special effects indicated by a wide chemical shift range and broadened signals. Paramagnetism diminishes the resolution of an NMR spectrum to the extent that coupling is rarely resolved. Nonetheless spectra of paramagnetic compounds provide insight into the bonding and structure of the sample. For example, the broadening of signals is compensated in part by the wide chemical shift range (often 200 ppm in 1H NMR). Since paramagnetism leads to shorter relaxation times (T1), the rate of spectral acquisition can be high.

Nanalysis Scientific Corp. is a scientific instrument manufacturer based in Calgary, AB, Canada. Established in 2009, Nanalysis specializes in the production of compact Nuclear Magnetic Resonance (NMR) spectroscopic instrumentation. As a new public company it is trading on the TSX Venture Exchange (TSXV) under the ticker symbol NSCI since June 2019, and later on the Frankfurt Stock Exchange (FRA) under the ticker symbol 1N1.

<span class="mw-page-title-main">Platinum-195 nuclear magnetic resonance</span>

Platinum-195 nuclear magnetic resonance spectroscopy is a spectroscopic technique which is used for the detection and characterisation of platinum compounds. The sensitivity of the technique and therefore its diagnostic utility have increased significantly starting from the 1970s, with 195Pt NMR nowadays considered the method of choice for structural elucidation of Pt species in solution.

References

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  2. ↑ Tuttle, Brad. "Helium Prices Hit the Roof, Leaving Balloon Sales Deflated". Business.time.com. Retrieved 28 October 2018.
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  6. ↑ "Mobile Spinsolve Benchtop NMR Spectrometer Facilitates Undergraduate Teaching | Magritek". www.magritek.com. Retrieved 2017-08-06.
  7. ↑ Ibragimova, Elena; Ibragimov, Ilgis (2017). "The ELEGANT NMR Spectrometer". arXiv: 1706.00237 [physics.ins-det].
  8. ↑ "Second Order Effects in Coupled Systems".
  9. ↑ Stephenson, David S., and Gerhard Binsch. "Automated analysis of high-resolution NMR spectra. I. Principles and computational strategy." Journal of Magnetic Resonance 37.3 (1980): 395-407
  10. ↑ Napolitano, José G., et al. "Complete 1H NMR spectral analysis of ten chemical markers of Ginkgo biloba." Magnetic Resonance in Chemistry 50.8 (2012): 569-575
  11. ↑ Jacobsen, N. E., “NMR Spectroscopy Explained: Simplified Theory, Applications and Examples for Organic Chemistry and Structural Biology” 2007, John Wiley & Sons, Inc.: Hoboken, New Jersey
  12. ↑ Friebolin, H. “Basic One- and Two-Dimensional NMR Spectroscopy” 5th Edition 2011, Wiley-VCH: Germany
  13. ↑ Berger, S; Braun, S.; “200 and more NMR Experiments: A Practical Course” 2004 Wiley-VCH: Germany
  14. ↑ "Nanalysis sample experiments for teaching NMR to undergraduates". Archived from the original on 2013-08-21. Retrieved 2013-06-10.
  15. ↑ “Process NMR Spectroscopy: Technology and On-line Applications” John C. Edwards, and Paul J. Giammatteo, Chapter 10 in Process Analytical Technology: Spectroscopic Tools and Implementation Strategies for the Chemical and Pharmaceutical Industries, 2nd Ed., Editor Katherine Bakeev, Blackwell-Wiley, 2010
  16. ↑ “A Review of Applications of NMR Spectroscopy in Petroleum Chemistry” John C. Edwards, Chapter 16 in Monograph 9 on Spectroscopic Analysis of Petroleum Products and Lubricants, Editor: Kishore Nadkarni, ASTM Books, 2011.
  17. ↑ Magritek. "Spinsolve 90".
  18. ↑ Magritek. "Spinsolve 80 Benchtop NMR Brochure Download". Go.magritek.com. Retrieved 2017-08-06.
  19. ↑ Magritek. "Spinsolve 60".
  20. ↑ Magritek. "Spinsolve ULTRA Benchtop NMR Brochure Download". Go.magritek.com. Retrieved 2017-08-06.
  21. ↑ "Multiple X Nuclei".
  22. ↑ "Diffusion PDF Gradients".
  23. ↑ "Thermo Fisher Scientific Corporate Newsroom". News.thermofisher.com. Retrieved 28 October 2018.
  24. ↑ "Thermo Fisher Scientific picoSpin FAQ" (PDF). Archived (PDF) from the original on 2021-10-17.
  25. ↑ "X-Pulse is the world's first benchtop NMR system to offer true multinuclear capability - Magnetic Resonance". Oxford Instruments. Retrieved 2020-02-18.
  26. ↑ "Oxford Pulsar Specification Sheet" (PDF). Acs.expoplanner.com. Archived from the original (PDF) on 2017-08-07.
  27. ↑ "Benchtop NMR | Spectrometer | Nuclear Magnetic Resonance". Bruker.com. Retrieved 12 August 2020.
  28. ↑ Q Magnetics. "QM-125".
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