Ion detecting apparatus and methods

An ion barrier mobility spectrometer apparatus comprising:

• a) a source electrode;
• b) a source shield electrode;
• c) said source electrode and said source shield electrode operating at similar voltages;
• d) an ion barrier electrode downstream from said source electrode, said ion barrier electrode operating at a relative voltage so as to create an ion barrier at a downstream end of an electric field gradient;
• e) said ion barrier further positioning said ions;
• f) means for releasing said positioned ions from said ion barrier;
• and
• g) a detector for detecting said released ions.

An ion barrier mobility spectrometer apparatus, comprising:

• a) a first source shield electrode;
• b) a second source electrode downstream from said source shield electrode;
• c) said source electrode and said source shield electrode operating at similar voltages;
• d) a third collection well electrode downstream from said source electrode;
• e) a fourth electrode downstream from said third electrode;
• f) a fifth trigger well electrode downstream from said fourth electrode;
• g) a plurality of electrodes downstream from said fifth electrode, said plurality of electrodes together comprising a means for creating a decreasing voltage gradient;
• and
• h) a detector downstream from said plurality of electrodes.

A method to predict sensitivity improvement for ion detection in a drift tube apparatus, comprising:

• a) introducing a plurality of ions at an upstream location of an electric field gradient;
• b) creating an ion barrier at a downstream location of said electric field gradient;
• c) measuring a quantity of time required for each of said plurality of ions to travel from said upstream location to said ion barrier;
• d) adding up the quantity of time measured in step (c) for all of said plurality of ions to obtain a sum total, said sum total representing a relative value;
• and
• e) comparing said relative value to a second relative value to create a ratio, said ratio representing a sensitivity improvement for ion detection.