Patent ID: 7518108

Claim:
An ion source for preparing analyte ions from a liquid sample containing a carrier liquid, said ion source comprising: an electrically charged droplet source for generating electrically charged droplets from the liquid sample, wherein at least partial evaporation of said carrier liquid from the electrically charged droplets generates analyte ions; a charge reduction chamber in fluid communication with the electrically charged droplet source, said charge reduction chamber provided as a chamber separate from said electrically charged droplet source and positioned for receiving and reducing the charge of the electrically charged droplets, analyte ions, or both; and a charge reduction reagent ion source in fluid communication with said charge reduction chamber and positioned outside of said charge reduction chamber, said charge reduction reagent ion source comprising: a means for generating a flow of a precursor gas; and a means for generating reagent ions from said precursor gas, wherein said flow of precursor gas passes through said means for generating reagent ions, thereby generating reagent ions which are transported into said charge reduction chamber and react with electrically charged droplets, analyte ions or both in the charge reduction chamber to change the charge-state distribution of the analyte ions; wherein said means for generating a flow of a precursor gas is selectively adjustable to control the charge-state distribution of said analyte ions.