A method of inhibiting the reaction between ions of opposite polarity is
disclosed. The method includes exposing a population of ions to a
resonance excitation frequency during a mass-to-charge altering reaction
between a first subpopulation of ions and a second subpopulation of ions,
the resonance excitation frequency being tuned to inhibit the
mass-to-charge altering reaction between an ion of the first
subpopulation of ions having a predetermined mass-to-charge ratio and an
ion of the second subpopulation of ions so that when an ion of the first
subpopulation of ions attains the predetermined mass-to-charge ratio, the
ion having the predetermined mass-to-charge ratio is selectively
inhibited from reacting with ions of the second subpopulation of ions.