Ultrahigh-Throughput ESI-MS: Sampling Pushed to Six Samples per Second by Acoustic Ejection Mass Spectrometry

Area of Science:

• Analytical Chemistry
• Mass Spectrometry
• Biotechnology

Background:

• Conventional mass spectrometry techniques (ESI, MALDI) face limitations in speed, reproducibility, and sample preparation.
• Existing methods can suffer from carryover, ion suppression, and high sample consumption, hindering high-throughput applications.
• There is a need for faster, more efficient sample injection methods for mass spectrometry-based screening.

Purpose of the Study:

• To present a novel acoustic ejection mass spectrometry (AEMS) setup for contactless sample injection.
• To evaluate the performance of AEMS for high-throughput screening (HTS) applications, including drug metabolism and pharmacokinetics (DMPK) analysis.
• To demonstrate AEMS's potential to overcome limitations of current mass spectrometry approaches.

Main Methods:

• Integration of an open port interface (OPI) with a modified acoustic droplet ejection (ADE) system for direct sample transfer from 384-well plates.
• Optimization of hardware for reduced transfer distance between OPI and ESI electrode.
• Performance evaluation through stress tests simulating label-free DMPK analysis and HTS campaigns, assessing ion suppression and system endurance.

Main Results:

• Achieved a maximum sampling rate of 6 Hz for dextromethorphan and d3-dextrorphan, with high reproducibility (%RSD of 7.7/7.5%) over 1152 injections.
• Demonstrated signal suppression of 51/73% in the presence of enzyme assay buffer and dog plasma, with low %RSD (5.7/6.7%).
• Exhibited system endurance with over 25,000 injections using an HTS buffer, showing minor OPI pollution and stable signals (%RSD = 8.5%).

Conclusions:

• The AEMS setup enables significantly faster and contactless sample injection for electrospray ionization mass spectrometry (ESI-MS).
• This technique addresses key bottlenecks in mass spectrometry, including speed, carryover, and sample preparation.
• The optimized AEMS system demonstrates high-throughput performance suitable for automated ESI-MS-based HTS.