ONLINE COUPLING OF SUPERCRITICAL-FLUID CHROMATOGRAPHY AND PROTON HIGH-FIELD NUCLEAR-MAGNETIC-RESONANCE SPECTROSCOPY

The direct on-line coupling of supercritical fluid chromatography and proton high-field nuclear magnetic resonance spectroscopy is demonstrated. For this purpose, a specially designed pressure-proof continuous-flow probe head has been developed, from which a signal line width of 1.5 Hz can be obtained in the supercritical state. A separation of phthalates is carried out under supercritical conditions with carbon dioxide as eluent and is monitored on-line with H-1 NRIR on a 400-MHz NMR instrument. All the components can be identified from their NMR spectra. The advantage of carbon dioxide as eluent is that the whole spectral range of the H-1 NMR spectra can be observed and no solvent suppression techniques are necessary to obtain the MMR spectre. Continuous-flow H-1 NMR spectra acquired under supercritical conditions are of the same quality as those recorded in liquids.