Combined liquid chromatograph/mass spectrometer for involatile biological samples.

A new liquid chromatograph/mass spectrometer has been developed in our laboratory for application to analysis of biological molecules of extremely low volatility. Oxyhydrogen flames rapidly vaporize the total liquid-chromatographic effluent, and molecular and particle beam techniques are used to efficiently transfer the sample to the ionization source of the mass spectrometer. This new instrument is comparable in cost and complexity to a combined gas chromatograph/mass spectrometer, but extends the capabilities of combined chromatography/mass spectrometry to a broad range of compounds not previously accessible. We are currently testing biologically significant samples with this instrument, using reversed-phase liquid-chromatographic separation and both positive and negative ion chemical-ionization mass spectrometry. Results have been obtained from mixtures of nucleic acid components--bases, nucleosides, and nucleotides--and from amino acids, peptides, saccharides, fatty acids, vitamins, and antibiotics. In all cases investigated to date, ions indicative of molecular mass are obtained in at least one of the operating modes available. Detection limits are typically in the 1-10 ng range for full mass scans (about 80-600 amu); sub-nanogram quantities are usually detectable with single-ion monitoring.