Pressurized sample infusion: An easily calibrated, low volume pumping system for ESI-MS analysis of reactions

Pressurized sample infusion (PSI) continuously delivers solution from a flask through capillary tubing at a flow rate that makes it suitable as a low internal volume pumping method for electrospray ionization mass spectrometry (ESI-MS). The flow rate can be predicted from the applied pressure by using the Hagen–Poiseuille equation, but variability in internal diameter of the PEEK tubing used is such that each individual length should be calibrated if accurate results are sought. Once calibrated, the values hold well for different solvents across a range of pressures. The technique has been exemplified in two reactions: the deprotection of a protected amino acid using trifluoroacetic acid, and in the platinum-catalyzed redistribution of two silanes. In both cases, the abundances of starting material, product(s) and intermediates were tracked in real time as the reaction proceeded.

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► Online reaction monitoring is enabled by pressurized sample infusion.
► Abundances of reactants, products and intermediates can be tracked in real time.
► Simple flow rate experiments provide an accurate estimate of internal diameter of tubing.