COLLEGEVILLE, Pa.—Whether at small- or large-scale, medicinal chemists would like to be able to monitor the progress of organic synthesis reactions both quickly and easily. To address this challenge, scientists at Wyeth Research and IonSense recently applied the MS-based direct analysis in real time (DART) method to the analysis of small molecules in drug discovery, comparing the results to the more laborious and time-consuming LC/UV/ESI-MS method.
As they describe in Analytical Chemistry, the DART ion source is held orthogonal to the inlet of a quadrupole mass spectrometer, with a melting point tube held in a helium gas stream connecting the two. Dipping the melting point tube into an analyte solution, the researchers then ionize µL volumes of the compound(s) for analysis in the mass spectrometer.
With samples of commercially available drugs, the researchers found that while DART produced spectral intensities one to two orders of magnitude weaker than ESI, the spectra themselves were identical and could easily be used to identify the compounds involved. Also, as a tool to monitor a synthetic transformation reaction, DART offered ion signal intensities for reactants and products that could be used for quantitative reaction monitoring.