Monitoring ongoing chemical reactions using eco-friendly miniature ambient ionization mass spectrometry

• TD-ESI coupled with a DLIT-MS has been developed for monitoring of ongoing chemical reactions. • Using eco-friendly, miniature ambient ionization mass spectrometry demonstrates effectiveness in tracking condensation and Tröger's base formation. • Its compact design minimizes waste and energy consumption, aligning with the principles of green chemistry. An analytical technique that combined probe sampling with thermal desorption electrospray ionization mass spectrometry (TD-ESI/MS) was developed to monitor ongoing chemical reactions. For each sample analysis, two microliters of sample solution were applied onto a metal wire. A direct current (DC) was applied to the wire, rapidly heating the sample solution and generating numerous small droplets and analyte molecules. The desorbed analytes were subsequently delivered into an ESI plume, interacting with charged solvent species to form analyte ions. A miniature ion trap mass analyzer was attached to the ion source to detect analyte ions. The entire analysis takes less than 15 s. Due to its capability for fast sampling and detection of chemical compounds, TD-ESI/MS was used to monitor a condensation reaction and formation of Tröger's base by detecting the respective reactant, product, and intermediate ion signals at different reaction times. In addition, the compact design and low power consumption of the TD-ESI/MS system makes it a highly suitable technique for on-site and decentralized applications like monitoring ongoing chemical reactions in general and organic chemistry laboratories for undergraduate students.