Hyphenation of capillary separations with nuclear magnetic resonance spectroscopy

The hyphenation of small-volume separations to information-rich detection offers the promise of unmatched analytical information on the components of complex mixtures. Nuclear magnetic resonance (NMR) spectroscopy provides information about molecular structure, although sensitivity remains an issue for on-line NMR detection. This is especially true when hyphenating NMR to capillary separations as the observation time and analyte mass are decreased to the point where reduced information is obtained from the eluting analytes. Because of these limitations, advances in instrumental performance have a large impact on the overall performance of a separation–NMR system. Instrumental aspects and the capabilities of cLC–NMR, CEC–NMR and CE–NMR are reviewed, and applications that have used this technology highlighted. Recent trends towards small volume capillary scale separations are emphasized, as is the recent success of capillary-isotachophoresis (cITP)–NMR.