JEOL Resources

High-Resolution Analysis of Carbon-Fluorine Couplings

Wed, 08 Jul 2026 15:04:53 GMT

Application note NM260006
Product used: Nuclear Magnetic Resonance (NMR)

Fluorinated organic molecules exhibit complex and often unusually large carbon-fluorine coupling constraints (J_CF) that differ markedly from the coupling patterns observed in proton-based systems. Accurate measurement of these couplings is essential for structural elucidation, conformational analysis, and validation of computational models in fluorine-rich chemical environments. This application note demonstrates a streamlined approach for determining both one-bond and long-range JCF values using 1D ¹³C NMR with selective ¹⁹F decoupling, enabled by the high ¹³C sensitivity and ¹H&¹⁹F dual-channel decoupling capabilities of the SuperCOOL MARVEL HFX Duo probe. The method leverages the wide chemical shift dispersion of ¹⁹F nuclei, which allows highly selective decoupling with minimal off-target excitation. A 53 mg sample of perfluoroaromatic model compound N,N-dimethylamino-2,5,6-trifluoro-3,4-phthalonitrile was used to illustrate the workflow using 500 MHz SuperCOOL MARVEL HFX Duo probe.

Exploiting 13C-13C scalar couplings at natural abundance

Wed, 08 Jul 2026 14:51:24 GMT

Application note NM260005
Product used: Nuclear Magnetic Resonance (NMR)

Classic INADEQUATE and ADEQUATE experiments are powerful tools for mapping the carbon backbone of organic molecules. However, their sensitivity is inherently low due to reliance on adjacent carbon atoms both being the rare ¹³C isotope - resulting in observable signals from only about 1 in 10,000 molecules.

JEOL's new SuperCOOL MARVEL probe offers exceptional sensitivity for both low-band (X) and high-band nuclei (¹H/¹⁹F), enabling acquisition of INADEQUATE and ADEQUATE-style experiments on moderate sample amounts within reasonable timeframes. This note outlines practical guidelines for acquiring high-quality data using 25 mg of Estradiol (MW 272.38) using 500 MHz SuperCOOL MARVEL probe as an example.

Change in ESR line-shape with solvent (1)

Wed, 08 Jul 2026 14:40:03 GMT

Application note NM260004
Product used: Nuclear Magnetic Resonance (NMR)

Fast and simple NMR Assignments of Antibiotic

Carbohydrate-based antibiotics are common and potent tools for fighting a large variety of infections. Repeating carbohydrtae fragments often result in significantly overlapping signal regions in ¹H NMR spectra of these compounds which complicates the NMR data analysis. Utilization of the added chemical shift dispersion of the ¹³C nuceli can simplify the assigment process at a cost of reduced sensitivity caused by low ¹³C natural abundance. A boost in sensitivity provided by JEOL's modern cryogenically cooled NMR probe technology dramatically reduces the time and effort required to assign NMR signals.

In this Application Note we present an example of hot to efficiently obtain a set of full ¹³C&¹H assignments of Kanamycin-A disulfate (MW ~880 Da), using only 1 mg of the antibiotic and four basic NMR experiments and utilizing JEOL's new nitrogen-cooled SuperCool MARVEL probe.

Change in ESR line-shape with solvent (2)

Wed, 08 Jul 2026 14:27:46 GMT

Application note ER260004E
Product used: Electron Spin Resonance (ESR)

ESR signal of nitroxide radical in solution

The linewidth of ESR signals from radicals in solutions is influenced by the molecular mobility of the radical species. In addition, hyperfine structure is observed because of interactions between the unpaired electron and surrounding nuclei. Three types of nitroxide radicals were dissolved in ultra-pure water and toluene at a concentration of 1.0 x 10^-4 mol/L, and ESR measurements were performed under identical experimental conditions. Comparison of the ESR signals revealed that, in ultra-pure water, the g-values are smaller, the A-values are larger, and the linewidths are narrower (Table 1 and Figure 1). This behavior is attributed to the lower viscosity and reduced intermolecular collisions in ultra-pure water compared with toluene, which allow solute molecules to undergo rapid rotation and diffusion. Nitroxide radicals exhibit anisotropic g-values and hyperfine interactions depending on their molecular orientation relative to the magnetic field. However, in aqueous solutions, molecular motion is sufficiently fast on the ESR timescale to result in effective averaging of this orientational anisotropy. Consequently, motional narrowing occurs, as all molecules experience an equivalent magnetic field, leading to sharp ESR signals.

Necessity for calibration of ESR measurement sensitivity

Wed, 08 Jul 2026 14:12:01 GMT

Application note ER260003

ESR Measurement sensitivity correction

Quantitative ESR measurements aim to determine the concentration and number of unpaired spins in a sample, providing valuable insights into radical concentrations and defect densities across various fields such as physics, chemistry, biology, geology, and materials science. ESR signal intensity depends on multiple factors, including sample properties, cavity Q-value, microwave field distribution and sample positioning, sample volume, and measurement conditions such as temperature.

To achieve accurate quantitative comparisons between samples, these factors must be properly accounted for to avoid artifacts caused by measurement conditions. Sensitivity correction typically involves calibration using a standard sample with a known spin concentration, normalization with a Mn marker, normalization by sample mass, volume, or amount, and temperature correction based on the Boltzmann distribution.

Performance highlights of MARVEL NMR probes

Mon, 29 Jun 2026 13:07:37 GMT

Introduction

Conventional liquid‑state NMR probes are typically built in one of two configurations: direct or inverse/indirect detection. In a direct probe, the innermost and most sensitive coil is tuned to an X‑nucleus (such as ³¹P, ¹³C, ¹⁵N), while the outer coil is tuned to ¹H. In an inverse probe, the inner coil is tuned to ¹H and/or to ¹⁹F, and the outer coil is tuned to X. Direct probes provide excellent X‑nucleus sensitivity with moderate ¹H/¹⁹F performance, whereas inverse probes deliver outstanding ¹H/¹⁹F sensitivity with moderate X‑channel sensitivity. Historically, spectroscopists have had to choose between these two designs based on the requirements of each experiment.

The JEOL SuperCOOL MARVEL probe introduces a new approach. This liquid‑nitrogen‑cooled, two‑channel probe features a high‑frequency (HF) channel that can be tuned to either 1H or 19F, and an X‑channel that covers nuclei resonating at frequencies of 31P and below. The result is a single probe that delivers exceptional sensitivity for both high‑ band and low‑ band nuclei.

This note highlights several key aspects of the SuperCOOL MARVEL probe’s performance that are central to modern NMR spectroscopy, including its sensitivity across multiple nuclei, its robust RF power‑handling capabilities, and its versatility in experiments involving ¹H, ¹⁹F, and X‑nuclei.

JNM-ECZL ECZ Luminous™ Series Accessories Catalog

Wed, 24 Jun 2026 08:35:05 GMT

Download the catalog via the link below.

Simplifying Scalar Coupling Measurements

Wed, 17 Jun 2026 19:21:38 GMT

The HECADE-HSQC experiment is specifically designed to measure heteronuclear scalar couplings such as nJCH and nJNH. While many methods can determine the magnitude of these couplings, HECADE is amongst the few that can also provide the sign of the coupling constant. Knowing the sign can be particularly helpful when determining molecular structure. For example, one-bond and three-bond CH couplings are generally positive, whereas two-bond and four-bond couplings may be either positive or negative. This distinction further aids in structural elucidation.

Fig. 1 HECADE – HSQC spectrum for a mixture of a mixture of a- and b- glucose acquired on a 400 MHz JEOL ECZL spectrometer with a 5mm ROYALPROBE^TMHFX

Fig. 2 Expansion of the HECADE – HSQC spectrum shown in Fig. 1 showing the long range JCH correlations from C1 to H2 and H3 of b -D-glucose

In a HECADE-HSQC spectrum, the sign of the coupling is indicated by the tilt of the peaks (as shown in Fig. 1). Peaks that tilt like a forward slash (“/”) represent positive couplings, while those tilting like a backslash (“¥”) represent negative couplings. The separation of peaks along the F1 dimension (the indirect dimension) corresponds to the large one-bond coupling.

Incorporating an isotropic mixing element into the experiment, that shares the magnetisation from one nucleus to each nucleus within a scalar coupled network allows for long range CH couplings to be measured via the signal separation in F2 (the direct dimension). For example, Fig. 2 shows an expansion of the data shown in Fig. 1 focusing on C1 of -D-glucose. The coupling of C1 – H2 (²J_CH) is -6.6 Hz and the C1 – H3 coupling (³J_CH) is 1.4 Hz.

Measuring Homonuclear Couplings

Homonuclear ¹H couplings hold equally rich structural information, but their extraction is often complicated by the narrow proton chemical-shift range and extensive multiplet overlap in ¹H spectra.

PSYCHE-2DJ,² an extension of the pure-shift PSYCHE method that suppresses homonuclear scalar couplings so that each chemical shift is ideally represented by a singlet, allows homonuclear scalar couplings to be measured in F1. In Fig. 3, PSYCHE-2DJ is applied to a mixture of α/β-D-glucose producing an F2 projection in which overlapping multiplets are collapsed into well-resolved singlets. Because all coupling information is retained, individual couplings can then be extracted.

Fg. 3 PSYCHE-2DJ spectrum of a mixture of /-D-glucose

However, even pure-shift techniques face challenges when strong overlap persists, particularly in the congested 3–4 ppm region. Various approaches have been proposed to simplify the extraction of homonuclear couplings, including G-SERF and PSYCHEDELIC.³ Both yield the full set of couplings associated with a selected resonance, with PSYCHEDELIC often providing higher sensitivity. Fig. 4 illustrates the 2D PSYCHEDELIC method applied by selecting the H1 resonance of α-D-glucose, where the separation in the F1 dimension corresponds to the ³J_(H1–H2) coupling of 3.76 Hz. As only couplings to selected nuclei are retained multiple experiments are typically required, one per region of interest with the condition that each region does not contain mutually coupled pairs of nuclei.

A drawback of these methods is the presence of strong axial peaks, which can obscure nearby couplings. Dong et al.⁴ introduced a simple processing scheme for PSYCHEDELIC-type data that effectively suppresses these artifacts. This method is summarised in Equation 1, where S_N/R represent the Normal and J-reversed spectra, respectively, and * denotes the complex conjugate.

S_new = (S_N-S_R) (S_R-S_N)

In contrast to the experiment used by Dong, we employ a triple spin-echo version of PSYCHEDELIC, which provides cleaner spectra. All processing is performed directly within the JASON* environment, avoiding the need for MATLAB post-processing. Applying the operation in Eq. 1 to the data in Fig. 4 produces the clean, axial-free spectrum shown in Fig. 5.

*JASON (JEOL Analytical Software Network)

Fig. 4 Expansion of the PSYCHEDELIC Spectrum showing the region from 3 – 4 ppm. The H1 signal of  -D-glucose was selected with a 80 Hz selective pulse (REBURP)

Fig. 5 The same data in Fig. 4 with the same expansion but with the processing summarised in Eq. 1 applied

References

W. Koźmiński, D. Nanz, J. Magn. Reson., 1997, 124, 383-392
M. Foroozandeh et al., Chem. Commun., 2015, 51, 15410-15413
D. Sinnaeve, Angew. Chem. Int. Ed Engl. 2015, 55, 1090-1093
X. Dong et al., J. Magn. Reson., 2021, 325, 10693

JNM-ECZL Series ECZ Luminous™ NMR Spectrometer

Wed, 16 Jul 2025 14:17:35 GMT

The JNM-ECZL series is an FT NMR system equipped with state-of-the-art digital and high-frequency technologies. The new Multi Frequency Drive System enables multi-resonance measurements in a standard configuration, providing a wider range of solutions. Welcome to the world of ECZ Luminous™.

Delta SpecScan-Daily

Tue, 15 Jul 2025 19:45:55 GMT

ECZ/ECZL Series daily inspection software that regularly diagnoses and calibrates the instrument, supporting stable daily operations and reducing the burden on instrument managers.

Features

Automatic resolution adjustment using dedicated samples
Scheduling
¹H & ¹³C pulse width check
Outputting inspection result reports
Automatic collection of device logs in the event of a problem
For system configuration and support cases, faster and more accurate support.

Package Contents

Delta SpecScan-Daily daily inspection software *
Dedicated spinner rotor for daily inspection
Dedicated sample for daily inspection

* One-year subscription. The NMR control software must be Delta v6.4 or later.