Parallel high‐throughput accurate mass measurement using a nine‐channel multiplexed electrospray liquid chromatography ultraviolet time‐of‐flight mass spectrometry system

A nine‐channel multiplexed electrospray (MUX) liquid chromatography ultraviolet time‐of‐flight mass spectrometry (LC/UV/TOFMS) system has been used to simultaneously measure accurate masses of eluting components from eight parallel gradient LC columns. Accuracies better than 5 and 10 ppm were achieved for 50 and 80% of samples, respectively, from a single batch analysis of ten plates (960 samples) of a Fmoc‐Asp(OtBu)‐OH and reserpine mixture. Combinatorial library compounds were analyzed using this parallel high‐throughput system in both positive and negative modes to rigorously verify expected products and identify side products. A mass accuracy of 10 ppm root mean square (RMS) is routinely obtained for combinatorial library samples from this high‐throughput accurate mass LC/MS system followed by automated data processing. This mass accuracy is critical in revealing combinatorial synthesis problems that would be missed by unit mass measurement. Copyright © 2003 John Wiley & Sons, Ltd.