Direct Liquid Introduction Interfaces

Abstract

The most obvious method for connecting a liquid Chromatograph and mass spectrometer is to couple them directly, i.e., direct liquid introduction (DLI). Tal’roze et al. [68TA28] were the first to publish a method for accomplishing this using nanoliter/minute flow rates from a glass capillary tube. Baldwin and McLafferty [73BA71] showed that a capillary tube containing a solute in a small volume of solvent (~10 μl) could be placed directly in a mass spectrometer source and used to generate chemical ionization spectra of the solute. Neither of these papers resulted in a practical LC/MS interface, but both demonstrated the attractiveness of the principle of direct coupling, giving rise to a literature rich in variations on this apparently simple and direct idea.