Abstract
In recent years, it has become increasingly interesting to understand the performance of mass spectrometers at pressures much higher than those employed with conventional operating conditions. This interest has been driven by several influences, including demand for the development of reducedβpower miniature mass spectrometers, desire for improved ion transfer into and through mass spectrometers, enhancedβyield preparative mass separations, and mass filtering at the atmospheric pressure interface. In this study, an instrument was configured to allow for the performance characterization of a rectilinear ion trap (RIT) at pressures up to 50 mtorr with air used as the buffer gas. The mass analysis efficiency, mass resolution, isolation efficiency, and collisionβinduced dissociation (CID) efficiency were evaluated at pressures ranging from 1 to 50 mtorr. The extent of degradation of mass resolution, isolation efficiency and ion stability as functions of pressure were characterized. Also, the optimal resonance ejection conditions were obtained at various pressures. Operations at 50 mtorr demonstrated improved CID efficiency in addition to peak widths of 2 and 5 m/z units (full width at halfβmaximum, FWHM) for protonated caffeine (m/z 195) and Ultramark (m/z 1521) respectively. Copyright Β© 2009 John Wiley & Sons, Ltd.