ABSTRACT
As in gas chromatography, the flame ionization detector (FID) is the detector commonly used in supercritical fluid chromatography (SFC) of carbohydrates and other organic compounds. 1 - 2 Recently, however, some success has been achieved in coupling SFC of carbohydrates to CI-mass spectrometry. 3 - 4 The microbore capillary column used in SFC is interfaced with the chemical ionization chamber of the mass spectrometer through an integral pressure restrictor, heated to about 280°C at the tip serving as the probe for MS. With ammonia as the reactant gas, selected ion monitoring of the [Μ + NH4]+ ions affords a detection method for trimethylsilylated or permethylated D-gluco-oligosaccharides that is far more sensitive than the FID; a detection limit of about 2 pmol has been claimed 4 for SFC-MS by this technique. The upper limit of molecular weight detectable is dependent upon the range of the mass spectrometer itself. With a low-voltage quadrupole instrument having a limit of 3000 D, 3 trimethylsilylated maltodextrins can be detected only to DP 7, but Reinhold et al. 4 have reported detection of the same oligosaccharides to DP 17 when the SFC column was coupled to a double-focusing magnetic sector mass spectrometer operating at 8 kV. SFC-MS has great potential as a sensitive analytical method in such applications as profiling glycoproteins and glycolipids and monitoring degradation of polysaccharides to homologous series of oligosaccharides.
