Gravitational sampling electrospray ionization mass spectrometry for real-time reaction monitoring.

Rationale: The elucidation of chemical reaction mechanisms has attracted tremendous interest in recent years. Here, gravitational sampling electrospray ionization mass spectrometry (GS-ESI-MS) is used to explore a simple method for the real-time monitoring of chemical and biochemical reactions.

Methods: A sample solution in a stainless steel sample well is directly delivered through a fused-silica capillary due to the forces of gravity, capillary action, and electroosmotic flow (EOF).