Optimized C-Trap Timing of an Orbitrap 240 Mass Spectrometer for High-Throughput Screening and Native MS by IR-MALDESI

Abstract

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.

Ultrahigh-Throughput Ambient MS: Direct Analysis at 22 Samples per Second by Infrared Matrix-Assisted Laser Desorption Electrospray Ionization Mass Spectrometry

“…We attribute this increase in carryover to analyte from the previous ablation event remaining suspended in the sample plume. This will tend to occur when the sampling time is shorter than the plume lifetime of ~50 ms, corresponding to 20 Hz sampling frequency 11 . A similar trend is seen when varying sampling frequency by running the MS at its maximum collection rate at different RP (Figure S 8).…”

Normalization techniques for high‐throughput screening by infrared matrix‐assisted laser desorption electrospray ionization mass spectrometry

“…The IR‐MALDESI source is currently coupled to an Orbitrap Exploris 240 mass spectrometer (Exploris 240, Thermo Fisher Scientific, Bremen, Germany). Electronic triggering of the Exploris 240, JGMA laser, and sample stage position were all controlled using RastirX, an in‐house software paired with an Arduino microcontroller 22,29 . A single burst of nine pulses (1.2 mJ/burst) from the JGMA 2970‐nm laser (Burlington, MA, USA) focused on the meniscus of the sample, which desorbed neutrals from the sample well plate.…”

“…Electronic triggering of the Exploris 240, JGMA laser, and sample stage position were all controlled using RastirX, an in-house software paired with an Arduino microcontroller. 22,29 A single burst of nine pulses (1.2 mJ/burst) from the JGMA…”

“…Infrared matrix‐assisted laser desorption electrospray ionization (IR‐MALDESI) is a hybrid, ambient ionization source that combines the benefits of electrospray Ionization (ESI) and MALDI 15–18 . IR‐MALDESI is commonly used for MS imaging applications but has also been characterized as a high‐throughput, direct analysis platform to analyze a diverse range of biochemical assays at a sub‐second per sample rate 15,16,19–22 . With IR‐MALDESI, neutral molecules are desorbed from a sample surface by a mid‐IR laser that resonantly excites the O‐H stretching bands of water, the sample matrix.…”

“… 15 , 16 , 17 , 18 IR‐MALDESI is commonly used for MS imaging applications but has also been characterized as a high‐throughput, direct analysis platform to analyze a diverse range of biochemical assays at a sub‐second per sample rate. 15 , 16 , 19 , 20 , 21 , 22 With IR‐MALDESI, neutral molecules are desorbed from a sample surface by a mid‐IR laser that resonantly excites the O‐H stretching bands of water, the sample matrix. The desorbed neutrals are intercepted by an orthogonally oriented electrospray plume, partition into the charged ESI droplets, and are then ionized in an ESI‐like manner.…”