Matrix‐assisted diffusion‐ordered spectroscopy: choosing a matrix

Abstract

Diffusion‐ordered spectroscopy (DOSY) is an important technique for separating the NMR signals of the components in a mixture, and relies on differences in diffusion coefficient. Standard DOSY experiments therefore struggle when the components of a mixture are of similar size, and hence diffuse at similar rates. Fortunately, the diffusion coefficients of solutes can be manipulated by changing the matrix in which they diffuse, using matrix components that interact differentially with them, a technique known as matrix‐assisted DOSY. In the present investigation, we evaluate the performance of a number of new, previously used, and mixed matrices with an informative test mixture: the three positional isomers of dihydroxybenzene. The aim of this work is to present the matrix‐assisted DOSY user with information about the potential utility of a set of matrices (and combinations of matrices), including ionic and non‐ionic surfactants, complexing agents, polymers, and mixed solvents. A variety of matrices improved the diffusion resolution of the signals of the test system, with the best separation achieved by mixed micelles of sodium dodecyl sulfate and cetyl trimethylammonium bromide. The use of mixed matrices offers great potential for the analyst to tailor the matrix to a particular sample under study. © 2016 The Authors Magnetic Resonance in Chemistry Published by John Wiley & Sons, Ltd.

Developments in the Reactivity of 2-Methylimidazolium Salts

“…To the initial mixture of 1,2-dimethyl-3-ethylimidazolium iodide ( 1b ) and base in CD 3 OD was added 1.0 equiv of benzaldehyde. Diffusion-ordered spectroscopy (DOSY) allows the separation of the NMR signals of different species according to their diffusion coefficients. , In Figure , it is possible to observe the DOSY spectra of the initial mixture (I) and after benzaldehyde addition (II). Before benzaldehyde (I) addition, only the imidazolium and methanol diffusion patterns were distinguished, whereas after benzaldehyde addition the immediate formation of adduct 6 took place as seen by the respective diffusion coefficient with 1 H signals.…”

Resolving DOSY spectra of isomers by methanol‐d4 solvent effects

“…cyclodextrins), metal complexes, micelles, (soluble) polymers or silica gel to the sample. General guidelines for the choice of matrix have been developed, and the technology has found applications, for instance, in the analysis of a flavonoids mixture . Nevertheless, addition of chromatographic medium may cause line shape distortions and additional spectral crowding and complicate the recovery of sample.…”

Separation of the α- and β-Anomers of Carbohydrates by Diffusion-Ordered NMR Spectroscopy

“…However, the DOSY method has generally failed to identify the isomeric species of similar size and structure because of their similar diffusion coefficients. Therefore, recent studies on the DOSY technique have focused on developing strategies for the separation of isomeric species [9][10][11][12][13][14]. The DOSY method has been also applied to carbohydrate chemistry as a tool for the separation and analysis of mono-, di-, oligo-, and polysaccharides, as well as for the structural analysis of metal-complexed carbohydrates [15][16][17][18][19][20].…”