Infrared matrix-assisted laser desorption ionization (IR-MALDESI) is a hybrid mass spectrometry ionization source that combines the benefits of electrospray ionization (ESI) and matrix-assisted laser desorption ionization (MALDI) making it a great analytical tool for high-throughput screening (HTS) analyses. IR-MALDESI is coupled to an Orbitrap Exploris 240 mass spectrometer that utilizes a bent quadrupole (C-trap) to inject accumulated ions into the high-field Orbitrap mass analyzer. Here, we present a study on the optimized C-trap timing for HTS analyses by IR-MALDESI mass spectrometry. The timing between initial ion generation and the C-trap opening time was optimized to reduce unnecessary ambient ion accumulation in the mass spectrometer. The time in which the C-trap was held open, the ion accumulation time, was further optimized to maximize the accumulation of analyte ions generated using IR-MALDESI. The resulting C-trap opening scheme benefits small-molecule HTS analyses by IR-MALDESI by maximizing target ion abundances, minimizing ambient ion abundances, and minimizing the total analysis time per sample. The proposed C-trap timing scheme for HTS does not translate to large molecules; a NIST monoclonal antibody standard reference material was analyzed to demonstrate that larger analytes require longer ion accumulation times and that IR-MALDESI can measure intact antibodies in their native state.
Keywords: C-trap; IR-MALDESI; Orbitrap mass spectrometer; high-throughput screening.