Secondary electrospray ionization

In 2007, the almost simultaneous works of Zenobi[3] and Pablo Sinues[4] applied SESI to breath analysis for the first time, marking the beginning of a fruitful field or research.

Detecting low volatility species in the gas phase is important because larger molecules tend to have higher biological significance.

: the droplet-vapor interaction model postulates that vapors are adsorbed in the electrospray ionization (ESI) droplets, and then reemitted as the droplet shrinks, just as regular liquid phase analytes are produced in electrospray ionization; on the other hand, the ion-vapor interaction model postulates that molecules and ions or small clusters collide, and the charge is transferred in this collision.

The main feature of SESI is that it can detect minuscule concentrations of low volatility species in real time, with molecular masses as high as 700 Da, falling in the realm of metabolomics.

SESI-MS has proven to be a robust technique for the identification of bacteria from cell cultures and infections in vivo from breath samples, after the development of libraries of vapor profiles.

[15][16] Metabolic profiling of breath samples has accurately differentiated healthy individuals from idiopathic pulmonary fibrosis[17] or obstructive sleep apnea patients.

[22] Recent studies show that secondary electrospray ionization (SESI) is a powerful technique to monitor drug kinetics via breath analysis.

Introducing known stimuli, such as specific metabolites isotopically labeled compounds, or other sources of stress triggers metabolic changes which can be easily monitored with SESI-MS.