Composition and Purity of Combinatorial Aryl Ether Collections Analyzed by Electrospray Mass Spectrometry

Electrospray mass spectrometry (ESI-MS), tandem mass spectrometry and on-line RP-HPLC-ESI-MS were used to evaluate the composition and purity of three different aryl ether mixtures consisting of 10 and 45 aryl ethers synthesized on solid support by Williamson etherification. The libraries feature two potential pharmacophores connected with three different spacers and serve as models for a detailed component analysis. Individual members of the library and by-products were identified rapidly and conveniently by product ion scans. Compound collections obtained by two different synthetic methods, the split/combine approach and the premix method, showed different mass distributions in the ESI-MS spectra. Some components were not detected in direct ESI-MS measurements, but were found by MS/MS experiments. Precursor ion and constant neutral loss scans allowed the identification of components with common structural features.