Patent ID: 7019291

Claim:
System for chemical analysis of a gas sample, comprising: a flow path, a soft ionization source, an ion filter including ion filter electrodes across said flow path, an electronic input, said electronic input coupled to said ion filter electrodes for generating a high-low varying asymmetric displacement field between said electrodes across said flow path, said asymmetric displacement field imparting transverse motion to said flow of ion species according to mobility characteristics of said ion species and according to extant field conditions, said transverse motion driving unwanted ion species in said flow of ion species into said ion filter electrodes for neutralization thereof, said asymmetric displacement field being compensated, said compensation for selecting at least one ion species out of said flow of ion species and accommodating travel of said selected ion species in said flow path to said ion outlet for detection without said neutralization, said ion filter distinguishing between ion species of an ionized NOx sample based on differences in ion mobility in said filter field, and said filter passing selected said ion species of said ionized NOx sample for detection based on said compensation, and said detected, passed, selected, ion species being identified based on historical detection data of said system and on said extant field conditions.