An interface has been developed for the direct coupling of Open Tubular Liquid Chromatography (OTLC) and Mass Spectrometry. The interface has similarities to both direct liquid introduction (DLI) and thermospray (TSP) interface designs. The interface is introduced into the vacuum system via the solid probe inlet; thus, it does not compromise the use of other inlet systems, such as GC, DLI, or direct probe. In this interface design, the capillary column passes through a probe inserted into the solid probe inlet. The end of the capillary column is tapered, creating a submicron exit orifice. The end of the capillary column passes through a copper heating block, the temperature of which can be controlled and monitored. Tapering the capillary column tip led to significant improvements in both the peak shape and sensitivity. Probe temperature also had a significant effect on these parameters. The system has been used with both glass and fused silica capillary columns, with inner diameters of 16 or 10 microns, respectively. With flow rates of nanoliters per minute, the entire effluent can be introduced into the mass spectrometer. When used with an electron-impact source, electron-impact mass spectra are produced. With a chemical ionization source, positive and negative CI spectra can be obtained when CI reagent gas is added through an inlet on the interface. The successful analysis of mixtures of organophosphorous pesticides, triazine herbicides, and polynuclear aromatic hydrocarbons has been demonstrated.
