Monitoring organic reactions with on-line atmospheric pressure ionization mass spectrometry: the hydrolysis of isatin

Time-resolved electrospray ionization mass spectrometry (ESI-MS) is a powerful tool for interrogating solution-phase reaction systems. Both mechanistic and kinetic information can be obtained using this technique. The title reaction offers the opportunity to examine the effects of different ionization scenarios with regard to monitoring reactant consumption and product formation. The hydrolysis of isatin was monitored in real time using a variety of ESI schemes: positive ion ([M + H](+), [M + Li](+), [M + Na](+)) and negative ion [M - H](-). The utility of each ionization approach, with respect to the spectral features afforded for reaction tracking was examined. A comparison of first-order hydrolysis kinetics data obtained using negative ion mass spectrometry is made with data acquired via an optical technique. Copyright (C) 2001 John Wiley & Sons, Ltd.