Patent ID: 6649907
Filing Date: 2003-11-18
Classification: H01J,Y10S

Abstract:
An ion source for preparing gas phase analyte ions from a liquid sample, containing chemical species in a solvent, carrier liquid or both, wherein the charge-state distribution of the gas phase analyte ions prepared may be selectively adjusted, said device comprising:a) an electrically charged droplet source for generation of a plurality of electrically charged droplets of the liquid sample in a flow of bath gas; b) a field desorption-charge reduction region of selected length, cooperatively connected to the electrically charged droplet source and positioned at a selected distance downstream with respect to the flow of bath gas for receiving the flow of bath gas and electrically charged droplets, wherein at least partial evaporation of solvent, carrier liquid or both from the droplets generates gas phase analyte ions and wherein the charged droplets, analyte ions or both remain in the field desorption-charge reduction region for a selected residence time; c) a reagent ion source, cooperatively connected and downstream of the electrically charged droplet source for generating electrons, reagent ions or both from the bath gas and which also generates an electric field, an electromagnetic field or both wherein the electrons, reagent ions or both react with droplets, analyte ions or both in the flow of bath gas within at least a portion of the field desorption-charge reduction region to reduce the charge-state distribution of the analyte ions in the flow of bath gas to generate gas phase analyte ions having a selected charge-state distribution; and d) a shield element surrounding the reagent ion source for substantially confining the electric field, electromagnetic field or both generated by the reagent ion source defining a shielded region wherein fields from the reagent ion source are minimized; wherein the residence time of droplets, analyte ions or both, the abundance of electrons, reagent ions, or both in the field desorption-charge reduction region, type of bath gas, reagent ion or both or any combinations thereof is adjusted to control the charge-state distribution of the output of the ion source.