Patent ID: 8217342

Claim:
A method to ionize vapors carried in a sample gas for analysis in an analytical instrument, the method comprising: providing an apparatus having an ionization chamber and an adjacent impaction chamber separated by an impaction plate having an impaction orifice defined therein; introducing said sample gas at a flow rate Q S into said ionization chamber including a source of charged particles, such that some among said vapors in said sample gas make contact with said charged particles to become ionized vapors; introducing clean gas into said impaction chamber; and, providing one or more electric fields such that some among said ionized vapors are guided through said impaction orifice, through said clean gas in said impaction chamber, and into an analytical instrument possessing an inlet orifice sampling an inlet flow rate Q A , wherein, said impaction orifice is configured such that said sample gas passes through said impaction orifice to define a jet therethrough extending into said impaction chamber, said jet minimizing the passage of said clean gas through said impaction orifice from said impaction chamber and into said ionization chamber, and wherein, said jet of sample gas collides against a jet of counterflow gas originating in said analytical instrument, both jets colliding in the impaction chamber such that penetration of said jet of counterflow gas into said ionization chamber is minimized.