Ion source and sample introduction method and apparatus using two stage ionization for producing sample gas ions

An apparatus for introducing ions into a detection or measurement means, comprising:

• a first section which comprises a first ionization region and a second ionization region downstream and separate from said first ionization region, means for introducing an ion source gas to said first section, means for ionizing at least a portion of said ion source gas within said first ionization region forming ion source ions, means for introducing a sample gas to said first section between said first ionization region and said second ionization region wherein said sample gas is prevented from entering said first ionization region, and means for contacting said ion source ions with at least a portion of said sample gas within said second ionization region forming sample gas ions;
• means for directing said sample gas ions from said first section to a second section and for directing any unionized portions of said ion source gas and said sample gas out of said first section;
• and
• said second section comprising means for introducing said sample gas ions into a detection or measurement means.