Simplified Analysis of Mixtures of Small Molecules by Chromatographic NMR Spectroscopy

Pagès, Guilhem; Delaurent, Corinne; Caldarelli, Stéfano

doi:10.1002/anie.200601622

Cited by 53 publications

(48 citation statements)

References 14 publications

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“…2). 27 Although the reason behind this puzzling result has not been unveiled yet, the possibility of using bare silica to produce separated NMR spectra largely simplify the applicability of chromatographic NMR in routine analysis. Along these lines, it could be conceived that any solid or immobilized phase could be used to induce the desired separation effect in the NMR spectrum once a suspect exists of a selective interaction between this immobile object and the target molecule.…”

Section: The Role Of the Solid Retardantmentioning

confidence: 98%

Chromatographic NMR: a tool for the analysis of mixtures of small molecules

Caldarelli

2007

Magn. Reson. Chem.

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The addition of a solid to a mixture of small molecules introduces variations on the average translational mobility of these latter, proportional to the affinity of a given moiety for the less-mobile phase. This effect is at the basis of chromatographic separation, but can be used to simplify the NMR analysis of mixtures as well. In fact, as the induced differences in molecular mobility can span orders of magnitude, it becomes a much easier task to split the overall NMR spectrum of the mixture into one of the pure components using pulsed field gradient (PFG) methods. We have demonstrated recently this approach, in the context of HRMAS (high-resolution magic angle spinning) NMR, as required to recover high-resolution spectra in solid/liquid mixtures. In this review, we shall cover some of the principles and the practicality of this HRMAS-PFG approach for the study of mixtures. A comparison of the actual (in LC) and virtual (in NMR) separation capabilities of a few combinations of solid phase material/solvent composition shows similarities but also some striking differences: bare (not functionalized) silica expresses a superior potential for resolving spectral components than expected on the basis of the LC outcome.

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Section: The Role Of the Solid Retardantmentioning

confidence: 98%

Chromatographic NMR: a tool for the analysis of mixtures of small molecules

Caldarelli

2007

Magn. Reson. Chem.

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“…The use of diffusion coefficient to separate mixtures is well documented, with the ability to resolve molecules with reasonably small differences in diffusion coefficient under favourable conditions; however, the technique is limited in cases of spectral overlap . In 2003, Caldarelli and co‐workers proposed a method to improve resolution in the diffusion dimension by the addition of a silica stationary phase normally used in HPLC . They showed that separation was improved and correlated with the degree of interaction between the analyte and stationary phase as predicted by traditional chromatographic models .…”

Section: Introductionmentioning

confidence: 99%

“…Several of the common sample modifiers proposed for a chromatographic NMR result in additional line broadening being observed, limiting the spectral resolution. This line broadening arises as a result of magnetic susceptibility differences between the particles of the stationary phase and the bulk solvent . Two approaches have been proposed to alleviate this line broadening and restore high resolution in the spectral dimension, in addition to the improved resolution in the diffusion dimension.…”

Section: Introductionmentioning

confidence: 99%

Size‐exclusion chromatographic NMR under HR‐MAS

Alcalde

Anderson

Day

2016

Magnetic Reson in Chemistry

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The addition of stationary phases or sample modifiers can be used to modify the separation achievable in the diffusion domain of diffusion NMR experiments or provide information on the nature of the analyte-sample modifier interaction. Unfortunately, the addition of insoluble chromatographic stationary phases can lead to line broadening and degradation in spectral resolution, largely because of differences in magnetic susceptibility between the sample and the stationary phase. High-resolution magic angle spinning (HR-MAS) techniques can be used to remove this broadening. Here, we attempt the application of HR-MAS to size-exclusion chromatographic NMR with limited success. Observed diffusion coefficients for polymer molecular weight reference standards are shown to be larger than those obtained on static samples. Further investigation reveals that under HR-MAS it is possible to obtain reasonably accurate estimates of diffusion coefficients, using either full rotor synchronisation or sophisticated pulse sequences. The requirement for restricting the sample to the centre of the MAS rotor to ensure homogeneous magnetic and RF fields is also tested. Copyright © 2016 John Wiley & Sons, Ltd.

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“…These additives modulate the observed diffusion coefficients as a result of some favourable interaction between the additive and the analyte of interest. In some cases, this can significantly improve the attainable resolution in the diffusion dimension . The exact nature of the interactions responsible for the diffusion modification is not fully understood.…”

Section: Introductionmentioning

confidence: 99%

“…Indeed, high mobile phase to stationary phase ratios are required to reproduce results that are consistent with on‐flow liquid chromatography . One minor drawback of adding a stationary phase to the NMR sample is the increased line width observed as a result of susceptibility broadening due to the mismatch in magnetic susceptibilities of the solvent and the stationary phase . Previous studies with small molecules have either utilised magic angle spinning or matching of the solvent magnetic susceptibility to that of the stationary phase to reduce the line broadening to acceptable levels.…”

Section: Introductionmentioning

confidence: 99%

Size‐exclusion chromatographic NMR of polymer mixtures

Alcalde

Joyce

Day

2014

Magnetic Reson in Chemistry

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The use of chromatographic stationary phases or solvent modifiers to modulate diffusion properties in NMR experiments is now well established. Their use can be to improve resolution in the diffusion domain or to provide an insight into analytemodifier interactions and hence the chromatography process. Here we extend previous work using size-exclusion chromatographic (SEC) stationary phases to the investigation of polymer mixtures. We demonstrate that similar diffusion modulation behaviour is observed with an SEC stationary phase which can be understood in terms of size-exclusion behaviour.3

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Simplified Analysis of Mixtures of Small Molecules by Chromatographic NMR Spectroscopy

Cited by 53 publications

References 14 publications

Chromatographic NMR: a tool for the analysis of mixtures of small molecules

Chromatographic NMR: a tool for the analysis of mixtures of small molecules

Size‐exclusion chromatographic NMR under HR‐MAS

Size‐exclusion chromatographic NMR of polymer mixtures

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