# US 6,764,857 B2 · Systems and methods for measuring nitrate levels > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 6,764,857 B2 - Document ID: US6764857B2 - Status: Granted - Kind: B2 - Application number: 10/267,807 - Filed: 2002-10-09 - Published: 2003-02-27 - Granted: 2004-07-20 - Earliest claimed: 1999-10-12 - Assignees: President and Fellows of Harvard College - Inventors: George A. Allen; Petros Koutrakis; Yiming Ding - Web page: https://patentgrep.com/patent/US6764857B2 ## CPC - G01N 31/005: {investigating the presence of an element by oxidation (G01N31/12 takes precedence)} - G01N 1/2205: {with filters} - G01N 33/0037: {NOx} - G01N 1/40: Concentrating samples - G01N 2001/2223: {aerosol sampling devices} - Y02A 50/20: Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters - Y10T 436/17: Nitrogen containing - Y10T 436/173076: Nitrite or nitrate - Y10T 436/176921: As part of an elemental analysis - G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q) - Y02A: TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE - Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION ## Abstract The systems and methods described herein relate to the measurement of nitrate levels in a sample of gas, for example, air, exhaust, or other sources of gas. Moreover, the systems and methods described herein are capable of operating using short sample collection periods, permitting rapid data collection and finely time-resolved nitrate monitoring over a span of time. Additionally, ambient nitrate can effectively be distinguished from other airborne particles, such as sulfate and carbon. ## Claims ### Claim 1 A system for measuring nitrate levels, comprising a first inlet for receiving a sample of gas, a collection body coupled to said first inlet, a filter mounted within said body, said filter interposed in the path of said sample of gas to collect particles from said sample of gas, a heater coupled to the body to heat the filter to volatilize the particles collected on the filter a cooling system coupled to the body to cool the collection body, a second inlet coupled to said body to provide a flow of gas through said body, an outlet for delivering said sample of gas from said collection body and a detector coupled to the outlet of said body to measure an NOx concentration. ### Claim 2 (depends on 1) The system of claim 1, further comprising a source of gas coupled to said second inlet. ### Claim 3 (depends on 2) The system of claim 2, wherein said gas is nitrogen. ### Claim 4 (depends on 2) The system of claim 2, wherein said gas is substantially free of oxygen. ### Claim 5 (depends on 1) The system of claim 1, further comprising a catalyst, coupled to said body and to said detector, capable of reducing NO2 to NO. ### Claim 6 (depends on 5) The system of claim 5, wherein said catalyst comprises molybdenum. ### Claim 7 (depends on 1) The system of claim 1, wherein said detector includes a light sensor. ### Claim 8 (depends on 7) The system of claim 7, wherein said detector further includes an ozone generator. ### Claim 9 (depends on 1) The system of claim 1, wherein said detector includes an infrared sensor. ### Claim 10 (depends on 1) The system of claim 1, wherein said detector includes a material which reversibly binds NO. ### Claim 11 (depends on 1) The system of claim 1, wherein said filter comprises quartz fibers. ### Claim 12 (depends on 1) The system of claim 1, further comprising an extractor coupled to said first inlet and to said collection body to substantially remove NO2 from the gas sample. ### Claim 13 (depends on 12) The system of claim 12, wherein the extractor comprises a hydroxyl-bearing solvent and a base. ### Claim 14 (depends on 12) The system of claim 12, further comprising a selection platform, situated between said first inlet and said extractor, to substantially remove particles larger than about 2.5 microns. ### Claim 15 (depends on 14) The system of claim 14, wherein said selection platform is a filter. ### Claim 16 (depends on 14) The system of claim 14, wherein said selection platform is an inertial impactor. ### Claim 17 A system for measuring nitrate levels, comprising a sample inlet to receive a sample of gas, an extractor coupled to said sample inlet to substantially remove NO2 from the gas sample, a collection body coupled to said sample inlet, an inertial impactor mounted within said body, said inertial impactor interposed in the path of said sample of gas to collect particles from the gas sample, a heater coupled to the body to heat the inertial impactor to volatilize the particles collected on the inertial impactor, a current source coupled to the inertial impactor to heat the inertial impactor and generate NOx, a cooling system coupled to the body to cool the collection body, and a detector coupled to a catalyst to measure an NOx concentration.