Source-Analyzer Interfaces Based on Ion Mobility

Both APCI and ESI produce low intensity background signals of the peak-at-every-mass type (Guo 2006) that can Unlit the S/B value and thus ultimately limits of detection and quantitation when MS monitoring is used (fuU scan or selected ion recording, SIR). One way to improve this situation is to use MS monitoring (MRM, Section 6.2.2), since it is unlikely that the background 

Another recent approach has been to insert an ion mobility device between the ion source and mass spectrometer. The additional separation power added by the differences in ion transit times through a buffer gas can often distinguish between analyte ions and the background ions that originate in the ion source (and thus can not be chromatographically separated). This multidimensional approach is feasible because of the differences in timescales among the HPLC peaks (seconds), ion mobility (tens of milliseconds) and SIR or MRM dwell times (a few 

A rather different way of exploiting differences in ion mobilities through a buffer gas is embodied in so-called High Field Asymmetric Waveform Ion Mobility Spectrometry (FAIMS), in which the physical property 

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