Objective:

To investigate the origins of unexplained ion signals in metabolomics and assess the role of microdroplet chemistry in the dark metabolome.

Key Findings:

• Over 50,000 signals detected in biological samples, far exceeding the expected 18,000 based on known metabolites.
• Only 5.3% of detected ions corresponded to simple adducts of known metabolites.
• Microdroplet chemistry contributes to the formation of artifact ions, which may undergo further fragmentation.

Interpretation:

Microdroplet-induced reactions significantly contribute to the unexplained signals in the dark metabolome, complementing the known in-source fragmentation effects.

Limitations:

• Further exploration of microdroplet reactions is needed to fully understand their contributions.
• The study primarily focuses on controlled experiments, which may not fully replicate complex biological systems.

Conclusion:

Microdroplet chemistry and in-source fragmentation together provide a more comprehensive understanding of the dark metabolome, highlighting the need for further investigation into unexplored reactions.