Automated sub-ppm mass accuracy on an ESI-TOF for use with drug discovery compound libraries

An automated, routine method to obtain sub-ppm accurate mass data on a benchtop electrospray ionization time-of-flight (ESI-TOF) mass spectrometer is described. Standards in the mass range 114 to 734 Da were analyzed over a 5-day period to demonstrate intra- and interday precision and mean mass accuracy less than 1 ppm. One hundred drug discovery pharmaceutical compounds were used to demonstrate an absolute average mass accuracy of 0.47 +/- 0.31 ppm. This is in contrast to previous reports of accurate mass analysis using time-of-flight mass spectrometry (TOFMS) technology that operates within 3 to 5 ppm. The same 100 samples were also analyzed using Fourier transform mass spectrometry (FTMS) technology and yielded comparable results to the TOFMS analysis.