Tandem-in-Time Mass Spectrometry Analysis Facilitated by Real-Time Pressure Adjustments

Abstract The pressure conditions are important for performing a variety of ion manipulations in mass spectrometers including ion transfer, ion dissociation and mass analysis. In contrast with lab-scale instruments, miniature mass spectrometers typically have simple configurations and reduced pumping power. In this study, a new design of configuration was implemented for a miniature ion trap mass spectrometer with a discontinuous atmospheric interface, realizing a real-time pressure adjustment within a single scan cycle to obtain optimal performance for different stages in a tandem-in-time mass analysis. Gas introduction from the connection between the turbo and rough pumps was used to elevate the vacuum pressure, with pinch valves and needle valves used to set the levels desirable. Pressures in a wide range from 0.01mtorr to 10mtorr could be set with great adjustability and stability. Multiple MS/MS analyses could be performed using a single ion introduction, with mass-selective ion transfer and collision induced dissociation at 2 mTorr while mass analysis below 0.5 mTorr.