A method for raising the resolving power, specificity, and peak capacity of conventional
ion mobility spectrometry is disclosed. Ions are separated in a dynamic
electric field comprising an oscillatory field wave and opposing
static field, or at least two counter propagating
waves with different parameters (amplitude, profile, frequency, or speed). As the functional dependencies of mean
drift velocity on the
ion mobility in a wave and
static field or in unequal
waves differ, only
single species is equilibrated while others drift in either direction and are mobility-separated. An
ion mobility spectrum over a limited range is then acquired by measuring ion drift times through a fixed distance inside the gas-filled
enclosure. The resolving power in the vicinity of equilibrium mobility substantially exceeds that for known traveling-wave or drift-tube IMS separations, with spectra over wider ranges obtainable by stitching multiple segments. The approach also enables low-cutoff, high-cutoff, and bandpass ion mobility filters.