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DOSY NMR Technique in Studies of Ionic-Liquid Gels and Aggregation of Asphaltenes

Diffusion ordered spectroscopy (DOSY) is a two-dimensional NMR technique, where one dimension reveals conventional chemical shifts and another dimension diffusion coefficients that can be correlated with molecular properties such as size, weight, shape, charge, etc. and that depend on molecular surrounding (temperature, viscosity, aggregation state) [1]. Moreover, the DOSY technique gained popularity in analysis of complex mixtures not only because of the non-destructive nature of NMR spectroscopy itself, but also due to its ability to perform the analysis without any prior separation of different components. Therefore the main two applications of the DOSY technique involve identification of different components in a complex mixture and determination of aggregation size. In one DOSY application it will be discussed how a high ionic conductivity of supramolecular ionic-liquid gels correlates with its cation and anion diffusion coefficients depending on gelator concentration (Figure 1) [2]. Another DOSY application presented will be a study of asphaltene aggregation in samples of crude oil and residues from atmospheric and vacuum distillation of crude oil. References: [1]C. S. Johnson Jr., Prog. NMR Spectrosc.34 (1999) 203-256. [2]A. Maršavelski, V. Smrečki, R. Vianello, M. Žinić, A. Moguš-Milanković, A. Šantić, Chem. Eur.J. 21 (2015) 12121–12128.

DOSY NMR ; ionic-liquid gel ; asphaltene aggregation

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