A mass spectrometer system, comprising: a first chamber that is maintained at atmospheric pressure, wherein said first chamber comprises a differential mobility spectrometer, a reagent ion generator coupled to said first chamber, said ion generator comprising: a hollow conduit extending from a proximal end to a distal end, wherein said proximal end is adapted for introducing reagent molecules from a source into said conduit and said distal end is disposed inside said first chamber, and an electrically conducting wire disposed at least partially within said hollow conduit and extending from a proximal portion to a distal tip portion, wherein said distal tip portion is positioned in proximity to said distal end of the conduit, and a voltage source adapted for electrically coupling to a portion of the wire for applying a voltage to said wire sufficient for causing an electric discharge in proximity of said distal tip portion of the wire; and a second chamber in communication via an orifice with said first chamber, said second chamber being maintained at a reduced pressure and housing a mass spectrometer; characterized in that said hollow conduit is configured as a throttle gas line terminating in proximity of said orifice connecting said first chamber to said second chamber and wherein said distal end of the hollow conduit is disposed in proximity of said orifice to allow delivering the reagent molecules to said first chamber in vicinity of said orifice, said throttle gas line configured to throttle the flow of a drift gas through the DMS to thereby control the residence time of ions therethrough. a first chamber that is maintained at atmospheric pressure, wherein said first chamber comprises a differential mobility spectrometer, a reagent ion generator coupled to said first chamber, said ion generator comprising: a hollow conduit extending from a proximal end to a distal end, wherein said proximal end is adapted for introducing reagent molecules from a source into said conduit and said distal end is disposed inside said first chamber, and an electrically conducting wire disposed at least partially within said hollow conduit and extending from a proximal portion to a distal tip portion, wherein said distal tip portion is positioned in proximity to said distal end of the conduit, and a voltage source adapted for electrically coupling to a portion of the wire for applying a voltage to said wire sufficient for causing an electric discharge in proximity of said distal tip portion of the wire; and a hollow conduit extending from a proximal end to a distal end, wherein said proximal end is adapted for introducing reagent molecules from a source into said conduit and said distal end is disposed inside said first chamber, and an electrically conducting wire disposed at least partially within said hollow conduit and extending from a proximal portion to a distal tip portion, wherein said distal tip portion is positioned in proximity to said distal end of the conduit, and a voltage source adapted for electrically coupling to a portion of the wire for applying a voltage to said wire sufficient for causing an electric discharge in proximity of said distal tip portion of the wire; and a second chamber in communication via an orifice with said first chamber, said second chamber being maintained at a reduced pressure and housing a mass spectrometer; characterized in that said hollow conduit is configured as a throttle gas line terminating in proximity of said orifice connecting said first chamber to said second chamber and wherein said distal end of the hollow conduit is disposed in proximity of said orifice to allow delivering the reagent molecules to said first chamber in vicinity of said orifice, said throttle gas line configured to throttle the flow of a drift gas through the DMS to thereby control the residence time of ions therethrough.