Abstract: The present invention relates to a method for determining the enantioselectivity of kinetic resolution processes and of asymmetrically proceeding reactions of prochiral compounds bearing enantiotopic groups by using isotope-labeled substrates so that the reaction products can be quantitatively determined with an isotope-specific detection system, e.g., an ESI mass spectrometer. In connection with automated sample charging, the method can be employed for high throughput screening. The relevant enantioselective conversions can be induced by chiral homogeneous or heterogeneous catalysts, biocatalysts or stoichiometric amounts of optically active agents.