# US 2019/0318921 A1 · Method and system of atmospheric pressure megavolt electrostatic field ionization desorption (apme-fid) > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2019/0318921 A1 - Document ID: US20190318921A1 - Status: Published application - Kind: A1 - Application number: 16/455,837 - Filed: 2019-06-28 - Published: 2019-10-17 - Earliest claimed: 2014-04-11 - Assignees: The University of Hong Kong - Applicants: The University of Hong Kong - Inventors: Kwan Ming Ng; Ho Wai Tang; Sin Heng Man - Web page: https://patentgrep.com/patent/US20190318921A1 ## CPC - H01J 49/168: {field ionisation, e.g. corona discharge (atmospheric pressure corona discharge per se H01T19/00)} - H01J 49/0422: {for gaseous samples (interfaces to gas chromatographs G01N30/7206)} - H01J 49/0431: {for liquid samples (interfaces to liquid chromatographs G01N30/7233)} - H01J 49/0459: {for solid samples} - H01J 49/16: using surface ionisation, e.g. field-, thermionic- or photo-emission - H01J 49/282: {using electrostatic analysers} - H01J 49/04: Arrangements for introducing or extracting samples to be analysed, e.g. vacuum locks; Arrangements for external adjustment of electron- or ion-optical components - H01J: ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS (spark-gaps H01T; electric arc lamps H05B31/00; particle accelerators H05H) ## Abstract On field ionization under ambient conditions is described and applied on both ionization and desorption of various chemicals and biochemical present on the surface of materials in solid, liquid or gas states. The Atmospheric Pressure Megavolt Electrostatic Field Ionization Desorption (APME-FID) method generates ions directly from the surface of samples connected to a high electrical voltage at megavolt conditions. Megavolt electrostatic potential is generated and gradually accumulated directly on the sample surface by a Van de Graaff generator without causing damage to the sample. Therefore, when coupled with mass spectrometric system, the APME-FID-MS method enables direct detection of analytes on the surface of samples in different sizes and diverse types. ## Claims ### Claim 1 A method of employing electrostatic potential, comprising: charging up samples for direct ionization of analyte molecules on sample surface, and desorption of the ions from sample surface for mass spectrometric detection. ### Claim 2 (depends on 1) The method of claim 1, wherein the electrostatic potential accumulated on the surface of a sample is a gradual accumulation process. ### Claim 3 (depends on 1) The method of claim 1 in which the samples are electrically isolated for the accumulation of electrostatic potential. ### Claim 4 (depends on 1) The method of claim 1 in which the magnitude of the electrostatic potential being applied on samples is tuneable. ### Claim 5 (depends on 1) The method of claim 1, wherein a replaceable sample probe containing analytes is analyzed, wherein the replaceable sample probe is directly immersed into sample for extraction of analytes, and the replaceable sample probe serves as sample storage. ### Claim 6 (depends on 1) The method of claim 1, wherein the sample material is of biological origin. ### Claim 7 (depends on 1) The method of claim 1, wherein the sample material is of non-living objects comprising different physical states, including gas, liquid, and solid. ### Claim 8 (depends on 1) The method of claim 1, wherein the method is compatible with sample material in variable size. ### Claim 9 (depends on 1) The method of claim 1, wherein the sample material is of objects comprising different physical shapes, including but not limited to sharp objects, blunt objects, and objects in irregular shapes. ### Claim 10 A method for analyzing samples comprises: generating megavolt electrostatic potential; directing electrostatic charge to a sample in a solid state; ionizing analyte molecules on the sample surface; desorbing analyte ions from the sample surface; transferring analyte ions to the inlet of a mass spectrometer; and detecting analyte ions by the mass spectrometer. ### Claim 11 (depends on 10) The method of claim 10, wherein generating the megavolt electrostatic potential is conducted using a Van de Graaff electrostatic generator. ### Claim 12 (depends on 10) The method of claim 10, with the proviso that detecting analyte ions is conducted without the use of an assisting reagent, a laser desorption technique, or a combination thereof. ### Claim 13 (depends on 11) The method of claim 11, with the proviso that detecting analyte ions is conducted without the use of an assisting reagent, a laser desorption technique, or a combination thereof. ### Claim 14 (depends on 10) The method of claim 10, further comprising directly connecting the sample to an apparatus for generating the megavolt electrostatic potential. ### Claim 15 (depends on 14) The method of claim 14, with the proviso that detecting analyte ions is conducted without the use of an assisting reagent, a laser desorption technique, or a combination thereof. ### Claim 16 (depends on 10) The method of claim 10, further comprising directing the megavolt electrostatic potential for generating megavolt electrostatic potential to the sample. ### Claim 17 (depends on 10) The method of claim 10, further comprising using a sample stage for holding a sample and directing the megavolt electrostatic potential to the sample. ### Claim 18 (depends on 10) The method of claim 10, further comprising using a sample transfer tubing for holding and directing gas and liquid samples close to the inlet of the mass spectrometer. ### Claim 19 (depends on 10) The method of claim 10, further comprising adjusting a distance between the mass spectrometer and the sample for collection of generated ions. ### Claim 20 (depends on 10) The method of claim 10, further comprising transferring the ions generated from sample to the inlet of the mass spectrometer using an ion transferring device.