Interface boosts MS Performance

Many popular mass spectrometry methods require an atmospheric-pressure interface to couple the ionization source to the mass analyzer. The typical configuration for the interface, which consists of an open channel and a series of differential pumping stages, has changed very little since it was first introduced. Such a configuration doesn't work well with mass analyzers with limited pumping capacities, such as miniaturized mass spectrometers. R. Graham Cooks, Zheng Ouyang, and Liang Gao of Purdue University have devised a discontinuous atmospheric-pressure interface (DAPI) that improves the performance of mass spectrometers with limited pumping capacity (Anal. Chem., DOI: 10.1021/ac800014v). DAPI links the ion source to the mass analyzer via two steel capillaries joined by silicone tubing. Gases are pulsed into the mass analyzer at high flow rates by pinching and releasing the silicone tubing. Using DAPI, the Purdue team connected various types of ionizers to a miniature rectilinear ion trap mass analyzer, with which they achieved part-per-billion limits of detection.