Utilizing Venturi effect for automated high-throughput droplet-MS from well plates.

Area of Science:

• Analytical Chemistry
• Biotechnology
• Mass Spectrometry

Background:

• High-throughput screening (HTS) is crucial for drug discovery, synthetic chemistry, and enzyme engineering.
• Well plates are standard for sample handling in HTS, necessitating compatible analytical methods.
• Mass spectrometry (MS) offers sensitive, selective, and label-free analysis suitable for HTS.

Purpose of the Study:

• To develop a Venturi-assisted droplet sampling method for direct well plate analysis using mass spectrometry.
• To integrate sample aspiration and electrospray ionization (ESI) into a single, valve-free step.
• To enhance throughput for HTS applications by optimizing sample transfer and minimizing carryover.

Main Methods:

• A Venturi effect generated by nebulizing gas flow withdraws droplet samples from well plates.
• Sample transfer occurs via a coaxial capillary, creating segmented flow with air gaps to prevent mixing.
• Automated x,y,z-positioning enables sampling from multiple wells; capillary dimensions and gas pressure optimize flow rate.

Main Results:

• The Venturi droplet-MS method achieved a throughput of 0.4 samples/s for screening 283 whole cell reactions.
• Low sample carryover (0.88 ± 0.16%) was observed using perfluoroalkoxy alkane (PFA) tubing.
• Results showed good agreement (R² = 0.92) with traditional liquid chromatography-mass spectrometry (LC-MS).

Conclusions:

• This integrated, valve-free Venturi droplet-MS system streamlines HTS by combining sample generation and transfer.
• The method requires no custom MS sources or specialized introduction equipment, offering a versatile HTS solution.
• This approach significantly improves upon existing segmented flow MS techniques for well plate-based screening.