Direct analysis in real time for reaction monitoring in drug discovery.

Direct analysis in real time (DART) is a novel ionization technique that provides for the rapid ionization of small molecules under ambient conditions. In this study, several commercially available drugs as well as actual compounds from drug discovery research were examined by LC/UV/ESI-MS and DART interfaced to a quadrupole mass spectrometer. For most compounds, the molecular ions observed by ESI-MS were observed by DART/MS. DART/MS was also studied as a means to quickly monitor synthetic organic reactions and to obtain nearly instantaneous molecular weight confirmations of final products in drug discovery. For simple, synthetic organic transformations, the trends in the intensities of the mass spectral signals for the reactant and product obtained by DART/MS scaled closely with those of the diode array or the total ion chromatogram obtained by LC/UV/ESI-MS. In summary, DART is a new tool that complements electrospray ionization for the rapid ionization and subsequent mass spectral analysis of compounds in drug discovery.