Mechanical Transport Devices

Abstract

Mechanical transport devices have in common the feature that the reduction in solvent volume and concurrent concentration of solute is performed in a region physically removed from the ion source of the mass spectrometer. Solutes are subsequently sequentially transported by some physical means into the ion volume for ionization and analysis. Devices of this type may be conveniently divided into two distinct categories: on the one hand, those which purport to offer a continuous representation of solute composition at the exit of the Chromatograph, termed continuous monitors, and, on the other hand, those which, by design, segment eluent into fractions which, following concentration, are presented to the spectrometric ion source. The latter, termed storage devices, may broadly be classified as mechanized fraction collection systems and are therefore not, in the strictest sense, direct liquid chromatographicmass spectrometric unions. In either case, within tolerable limits, systems have been demonstrated to exercise the requisite pressure reduction between Chromatograph and spectrometer. The requirements for pressure reduction are variable, being a function of the rate of liquid flow, the speed of transportation, the nature of the enrichment device used, and the pumping efficiency of individual systems. In any event, both of these approaches offer the significant theoretical advantage that the ionization of solutes can be made independent of any influence of the mobile phase. This virtue should not be underestimated.