Evaluation of mass spectrometric methods applicable to the direct analysis of non-peptide bead-bound combinatorial libraries

Electrospray, matrix-assisted laser desorption, and time-of-flight secondary ion mass spectrometry have been explored as possible methods for the identification of active members of molecular combinaterial libraries. All three methods are found to yield accurate molecular weight information about a target molecule angiotensin II antagonist synthesized on a 40-μm polystyrene bead. Structural identification is also possible by accurate mass measurements to eliminate candidate structures with the same nominal mass and by analysis of the fragmentation patterns. In addition, the secondary ion mass spectrometry measurements yield spatially resolved spectra from a single bead after exposure to a suitable gas which clips the covalent bond at the linking position. All three approaches appear to offer a viable screening strategy of non-peptide libraries without the use of additional molecular tags.