Identification of unknown components in a sample using a field asymmetric waveform ion mobility spectrometer (FAIMS), which enables simultaneous detection of positive and negative ions

摘要

The carrier gas carries the sample after ionization by ionization source (16) into the ion filter region (18). A dispersion voltage V DISP is applied across the filter electrodes (20,22) as an RF voltage driven between high and low field strength conditions, which causes the ions to move transverse to the flow. A compensation voltage, V COMP , causes a particular ion species to be returned toward the center of the flow path, thus being able to exit the filter without colliding with the filter electrodes. Since other species will collide with the filter electrodes, ions are discriminated from each other according to mobility. According to the invention even two ions, which are compensated by the same V DISP /V COMP - combination, can be discriminated if they have different polarities 17-, 17+, since electrodes (28,30) detect simultaneously both positive and negative ions.