Mass Transport of Volatile Molecules in Porous Materials: Evaporation–Condensation Phenomena Described by NMR Diffusometry

Carrara, Caroline; Pagès, Guilhem; Delaurent, Corinne; Viel, Stéphane; Caldarelli, Stéfano

doi:10.1021/jp2074607

Cited by 19 publications

(29 citation statements)

References 37 publications

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“…Using size‐exclusion chromatographic stationary phases under HR‐MAS yields unexpected results in that the observed diffusion coefficient is larger in the presence of the stationary phase. Evaporation–condensation, postulated previously for benzene–silica systems, is unlikely to be responsible. We confirm that it is possible to obtain reliable estimates of the diffusion coefficient under HR‐MAS conditions using either rotor synchronisation of the gradient pulses and delays or more sophisticated pulse sequences such as Oneshot .…”

Section: Discussionsupporting

confidence: 66%

“…the ratio of solution to stationary phase, has been shown to have a dramatic effect on the modulation of the diffusion coefficient caused by a given stationary phase . This effect is postulated to depend on whether mass transport is confined just to the intraparticle pores or whether there is sufficient solvent to allow escape into the interparticle space . In the case of the samples used here, the ratio of solution to stationary phase is high; therefore, the polymers are able to explore both the intraparticle and interparticle voids.…”

Section: Resultsmentioning

confidence: 95%

“…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 . The idea of adding a sample modifier has been proposed and utilised by a number of groups and is known as chromatographic NMR or matrix‐assisted DOSY .…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Discussionsupporting

confidence: 66%

Section: Resultsmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

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Size‐exclusion chromatographic NMR under HR‐MAS

Alcalde

Anderson

Day

2016

Magnetic Reson in Chemistry

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“…The exact nature of the interactions responsible for the diffusion modification is not fully understood. However, recent studies have shown that in the case of chromatographic NMR, the loading of the stationary phase, that is, the relative amount of stationary phase to ‘mobile phase’, plays an important role . Indeed, high mobile phase to stationary phase ratios are required to reproduce results that are consistent with on‐flow liquid chromatography .…”

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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“…This counterproductive effect can be contained by either spinning of the sample at the magic angle or by using solvents with the same susceptibility as the solid . In this way, the addition of solid chromatographic phases to NMR solution analysis has been employed to improve DOSY experiments or to understand retention mechanisms or transport mechanisms . At any rate, the resolution recorded by these procedures for heterogeneous mixtures is always worst than that for pure solutions, typically by an order of magnitude.…”

Section: Introductionmentioning

confidence: 99%

Molecular signal suppression byin situmicroextraction in nuclear magnetic resonance spectroscopy

2014

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The detailed characterization of complex mixtures by NMR is often hampered by the presence of signals from uninformative compounds, the resonances of which overlap with those of the molecules of interest. We provide here a proof of principle for an approach to NMR signal suppression in complex samples using Molecularly Imprinted Polymers (MIPS). Addition of a few milligrams of polymer to a solution traps the target molecule in typical micromolar to millimolar concentration, thus achieving in situ signal suppression, without altering any other spectral features. This method minimized any manipulation or perturbation of the spectrum and was applied to a complex mixture of known compounds and to a plant extract, in both cases spiked with a compound (bisphenol A), which was subsequently removed by selective binding to a complementary MIP. What is described in this report is comparable with microextraction and may in due course be applied to a large number of analytical challenges.

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Mass Transport of Volatile Molecules in Porous Materials: Evaporation–Condensation Phenomena Described by NMR Diffusometry

Cited by 19 publications

References 37 publications

Size‐exclusion chromatographic NMR under HR‐MAS

Size‐exclusion chromatographic NMR under HR‐MAS

Size‐exclusion chromatographic NMR of polymer mixtures

Molecular signal suppression byin situmicroextraction in nuclear magnetic resonance spectroscopy

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