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

We present an acoustic ejection mass spectrometry (AEMS) setup for ESI-MS based sample

injection at a sampling rate faster than current ESI and MALDI techniques. A modified acoustic

droplet ejection system was combined with an open port interface and a modified ESI source. To

simulate applications of drug metabolism and pharmacokinetics analysis and high-throughput

screening campaigns, two stress tests were performed regarding ion suppression and system

endurance in combination with minor sample preparation. Maximum sampling rate was 6 Hz for

dextromethorphan and d3-dextrorphan (each 100 nM) for 1152 injections in 63 s at FWHM of

105 ms and %RSD of 7.7%/7.5% without internal standard correction. Enzyme assay buffer and

crude dog plasma caused signal suppression of 51%/73% at %RSD of 5.7%/6.7% (n = 120) and

stable OPI performance during 1100 injections. An endurance buffer revealed minor OPI pollution

and constant signals for >25.000 injections (%RSD = 8.5%, n = 10,557).