METHOD AND APPARATUS FOR CONCENTRATING IONISED MOLECULES

The invention provides an apparatus for increasing a number concentration of molecules of an analyte of interest in real time from a sample gas flow containing ionised molecules of the analyte, aerosol particles and other molecules, the apparatus comprising:an ion-concentrating chamber having:an inlet for receiving the sample gas flow;an ion outlet; andat least one other outlet;the ion-concentrating chamber being connected or connectable to a gas flow generating and controlling device for establishing a gas flow velocity field within the ion-concentrating chamber to direct the aerosol particles and other molecules of the sample gas flow to the at least one other outlet; andone or more electrodes arranged in an axially spaced apart manner along the ion-concentrating chamber for creating an electric field within the ion-concentrating chamber to direct the ionised analyte molecules in the sample gas flow to the ion outlet, wherein the electrodes are configured such that an absolute value of the strength of the electric field increases progressively along the ion-concentrating chamber.