Patent ID: 8247765
Filing Date: 2012-08-21
Classification: G01N

Abstract:
1. Method for measuring gaseous substances, which method comprises the stages: ionization of the sample gas in a gas flow, leading of the ionized gas flow through an elongated ion-mobility measuring chamber, separation of ions with differing ion mobilities in the measuring chamber with the aid of a transverse electric field and at least one measurement-electrode pair arranged on the wall of the measuring chamber, characterized in that at a chosen distance in the flow direction before the measuring electrodes, the gas flow is divided into at least two part-flows for the pre-filtering of the ions, in which one of the part-flows at the chosen point is referred to as the emission flow, the other part-flows being referred to as shut-off flows, and when the ions are filtered out of the said ionized gas flow from each of the shut-off flows with the aid of a static electric field relative to the mobility of the ions, and at least the selected ions in the emission flow are permitted to enter the separation after the said pre-filtering, with the aid of a 0-field arranged in the emission flow.