MASS SPECTROMETER, INCLUDING COUPLING OF AN ATMOSPHERIC PRESSURE ION SOURCE TO A LOW PRESSURE MASS ANALYZER

摘要

A method of transporting ions from a region at a relatively high pressure to a region at a relatively low pressure comprises generating ions in a first region at a relatively high pressure, for example at atmospheric pressure. The ions are then passed from the first region into a second region containing a device comprising a pair of spaced apart electrodes, preferably a pair of cylinders, the second region being maintained at a relatively low pressure. An asymmetric RF voltage and a DC compensating voltage are applied to the electrodes, whereby ions of interest follow a stable trajectory through the electrodes, and the ions pass out of the space between the electrodes in the second region. Gas is displaced or pumped from the second region to maintain the second region at the relatively low pressure. The ions pass out of the second region into a third region maintained at a lower pressure than the first and second regions. A corresponding apparatus is provided.