Simple direct liquid introduction system usable as an interface for liquid chromatography-mass spectrometry on quadrupole and magnetic-sector mass spectrometers

Abstract

A simple and inexpensive direct liquid introduction system that can be used for tandem mass spectral analysis and for interfacing liquid chromatography on quadrupole and magnetic-sector mass spectrometers is described. The interface consists of a transfer fused-silica capillary that is introduced directly into the chemical ionization source of the mass spectrometer through the conventional gas chromatography-mass spectrometry interface, replacing the capillary column. The coupling uses no desolvation chamber and the transfer capillary is heated over the whole length of the interface. Experiments on the effect of interface temperature and flow-rate demonstrate that the system is extremely stable under optimal operating conditions, which are similar on different spectrometers. The chemical ionization plasma generated by the mobile phase under typical operation consists mainly of protonated monomers, and its composition is similar on different spectrometers, as shown by the comparison of spectra obtained. The system can be used with a series of mobile phases, and the ionization features that they produce are comparable. The system is stable, reproducible and allows picogram range sensitivity to be achieved in mass spectrometric, tandem mass spectrometric or liquid chromatographic-mass spectrometric experiments.