The Echo® MS system, developed by Sciex, uses Acoustic Ejection Mass Spectrometry (AEMS) that generates sample droplets and introduces small volumes of 2.5nL to the mass spectrometer via an Open Port Interface (OPI) (scalable to 25nL with multiple ejections) in a highly reproducible manner with minimal carryover. The process is chromatography-free, facilitating dramatic increases in throughput with the potential to run 1 second cycle times. Whilst this combination of low sample requirements and rapid cycle times has the potential to transform routine sample analysis current potential limitations include reduced sensitivity compared to conventional LC-MS/MS and interference due to lack of chromatographic separation.
At Cyprotex we have evaluated the Echo® MS technology for its application in routine ADME screening. We compared Echo® MS with established, routine LC-MS/MS methods for the analysis of samples generated from our microsomal stability and cytochrome P450 (CYP) inhibition assays. Prior to analysing the samples, the linearity and reproducibility of the sample ejection volume was assessed. Droplet linearity (assess over 1 to 10 droplets) was very good (R2 > 0.998) suggesting increased sample volume may be used when sensitivity is limited. Reproducibility was also good with typical co-efficient of variation based on peak area response being in the range of 5-10 % from different wells.
Samples for a set of 24 known drugs generated in the microsomal stability assay were analysed by both Echo® MS and conventional LC-MS/MS. Intrinsic clearance values were in excellent agreement between the two techniques and across a range of clearance values. For the CYP inhibition, the assay was performed in 7 isoforms using 8 substrates. Evaluation of CYP1A2 inhibition was found to be incompatible with the Echo® MS due to the in‑source conversion of phenacetin to acetaminophen. However, the majority of isoforms generated IC50 values which were in good agreement between the Echo® MS and LC-MS/MS data.
This research was presented as a poster at the European Bioanalysis Forum (EBF) in November 2022 in Barcelona. Read our poster to learn more about this research.