Charge reduction electrospray ionization ion source

A method 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 method comprising the steps of:

• a) producing a plurality of electrically charged droplets of the liquid sample in a flow of bath gas;
• b) passing the flow of bath gas and droplets through a field desorption-charge reduction region of selected length, wherein at least partial evaporation of solvent, carrier liquid or both from 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) exposing the droplets, gas phase analyte ions or both to electrons, reagent ions or both generated from bath gas molecules by a reagent ion source that generates an electric field, electromagnetic field or both and is surrounded by a shield element that substantially confines the electric field, electromagnetic field or both generated by the reagent ion source defining a shielded region wherein fields generated by the reagent ion source are minimized, wherein the electrons, reagent ions or both react with said droplets, charged droplets or both 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 thereby generating gas phase analyte ions having a selected charge-state distribution;
• and
• d) controlling the charge-state distribution of said gas phase analyte ions by adjusting the residence time of droplets, analyte ions or both, the abundance of electrons, reagent ions, or both, the type of bath gas, the type of reagent ion or both or any combinations thereof.

A device for determining the identity and concentration of chemical species in a liquid sample containing the chemical species in a solvent, carrier liquid or both, said device comprising:

• a) an electrically charged droplet source for generating 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 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 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 desortion-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;
• 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 generated by the reagent ion source are minimized;
• and
• e) a charged particle analyzer operationally connected to said field desorption-charge reduction region, for analyzing said gas phase analyte ions.
• 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 gas phase analyte ions.

A method for determining the identity and concentration of chemical species in a liquid sample containing the chemical species in a solvent, carrier liquid or both, said method comprising:

• a) producing a plurality of electrically charged droplets of the liquid sample in a flow of bath gas;
• b) passing the flow of bath gas and the droplets through a field desorption-charge reduction region of selected length, 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) exposing the droplets, gas phase analyte ions or both to electrons, reagent ions or both generated from bath gas molecules by a reagent ion source that generates an electric field, electromagnetic field or both and is surrounded by a shield element that substantially confines the electric field, electromagnetic field or both generated by the reagent ion source and defines a shielded region wherein fields generated by the reagent ion source are minimized, wherein the electrons, reagent ions or both react with said droplets, analyte ions or both 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 thereby generating gas phase analyte ions having a selected charge-state distribution;
• d) controlling the charge-state distribution of said gas phase analyte ions by adjusting the residence time of droplets, analyte ions or both, the abundance of electrons, reagent ions, or both, the type of bath gas, the type of reagent ion or both or any combinations thereof;
• and
• e) analyzing said gas phase analyte ions with a charged particle analyzer.

An electrospray ionization 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 electrospray chamber housing an electrospray droplet source for generating a plurality of electrically charged droplets of the liquid sample containing chemical species in a flow of bath gas;
• b) a field desorption-charge reduction region of selected length, cooperatively connected to the electrospray chamber 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 corona discharge cooperatively connected downstream of said electrospray chamber comprising an electrically biased wire electrode positioned sufficiently close to an electrically biased metal disc held substantially close to ground for generating electrons, reagent ions or both from the bath gas, wherein said wire electrode and said metal disc are arranged in a point to plane geometry and separated by a distance sufficiently close to create a self-sustained electrical gas discharge and 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 wire mesh screen surrounding the corona discharge for substantially confining the electric field, electromagnetic field or both generated by the corona discharge defining a shielded region wherein the fields 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.

A method of reducing the fragmentation of ions generated from electrospray discharge of a liquid sample, containing chemical species in a solvent, carrier liquid or both, said method comprising the steps of:

• a) producing a plurality of electrically charged droplets of the liquid sample in a flow of bath gas by electrospray discharge;
• b) passing the flow of bath gas containing the droplets through a field desorption-charge reduction region of selected length, wherein at least partial evaporation of solvent, carrier liquid or both from 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) exposing the droplets, gas phase analyte ions or both to electrons, reagent ions or both generated from bath gas molecules by a reagent ion source that generates an electric field, electromagnetic field or both and is surrounded by a shield element that substantially confines the electric field, electromagnetic field or both generated by the reagent ion source defining a shielded region wherein fields generated by the reagent ion source are minimized, wherein the electrons, reagent ions or both react with said droplets, analyte ions or both within at least a portion of the field desorption region to reduce the charge-state distribution of the analyte ions in the flow of bath gas thereby generating gas phase analyte ions having a selected charge-state distribution;
• and
• d) controlling the charge-state distribution of said gas phase analyte ions by adjusting the residence time of droplets, analyte ions or both, the abundance of electrons, reagent ions in the field desorption-charge reduction region, or both, the type of bath gas, the type of reagent ion or both or any combinations thereof.