REGULATION OF MULTIMER FORMATION IN ELECTROSPRAY MASS-SPECTROMETRY

Extensive multimer formation of small and uncharged analytes was obser ved in electrospray mass spectrometry. The concentration-dependent agg regation behavior, including species up to tetramers, resulted in high ly nonlinear calibration curves, For some analytes, these effects were operating down into the nanomolar level, Varying the drift potential failed to selectively dissociate the multimer complexes in favor of th e monomer, which severely obstructed quantitative work, However, by in corporating certain cationic additives into the electrosprayed solutio n, complete suppression of the multimers could be obtained. In additio n, a gain in the signal intensities by a factor up to 7 was achieved. A variety of additives were investigated, and the structural requireme nts for optimum performance will be outlined.