# US 6,623,699 B1 · Analyzing system for high accuracy nitrogen determination > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 6,623,699 B1 - Document ID: US6623699B1 - Status: Granted - Kind: B1 - Application number: 09/714,480 - Filed: 2000-11-15 - Granted: 2003-09-23 - Earliest claimed: 2000-11-15 - Assignees: Leco Corporation - Inventors: Brian W. Pack; Carlos Guerra; Peter M. Willis; Joel C. Mitchell - Web page: https://patentgrep.com/patent/US6623699B1 ## CPC - G01N 31/12: using combustion (G01N25/20 takes precedence) - G01N 33/0016: {by regulating a physical variable, e.g. pressure or temperature} - Y10T 436/17: Nitrogen containing - Y10T 436/176152: Total nitrogen determined - Y10T 436/176921: As part of an elemental analysis - Y10T 436/177692: Oxides of nitrogen - Y10T 436/178459: Only nitrogen dioxide - Y10T 436/179228: Both nitrogen oxide and dioxide - Y10T 436/186: Sulfur dioxide - Y10T 436/20: Oxygen containing - Y10T 436/204998: Inorganic carbon compounds - Y10T 436/205831: Carbon monoxide only - Y10T 436/207497: Molecular oxygen - 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) - Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION ## Abstract An analyzer compensates for gas flow perturbations by providing a makeup flow of carrier gas to maintain the pressure and/or flow rate of analyte and inert gas through a detector constant such that a accurate determination of a low concentration of an analyte in the presence of a high concentration of a second analyte can be accurately determined. In one embodiment, a carrier gas is introduced through a valve responsive to the detected pressure in the gas flow stream between a scrubber and a subsequent detector for maintaining the pressure constant during an analysis. In another embodiment of the invention, a flow transducer is positioned in the gas flow path between the scrubber and detector and coupled to a flow control valve coupled to introduce carrier gas as a function of detected gas flow such that the flow rate of gas into the detector is maintained constant. ## Claims ### Claim 1 An analyzer for the determination of the concentration of first and second analytes in a sample comprising: a furnace for combusting a sample into gaseous byproducts of combustion; a source of an inert carrier gas for sweeping the byproducts of combustion from said furnace to a detector for the detection of a first analyte; a scrubber coupled to the detector for removing the first analyte from the inert gas stream; a second detector coupled to the scrubber for detecting the second analyte; a conduit coupled from said source of carrier gas to the junction of said scrubber and second detector; a control valve coupled in said conduit between said source and said second detector; a pressure transducer coupled to said conduit; and a control circuit coupled to said pressure transducer for detecting the pressure thereof and providing an output control signal applied to said control valve to maintain the pressure in the flow path between said scrubber and said second detector substantially constant by controlling the flow of inert gas from said source when the scrubber tends to lower the pressure due to relatively high concentrations of a first analyte as compared to the second analyte. ### Claim 2 (depends on 1) The analyzer as defined in claim 1 wherein said first analyte is oxygen having a concentration of from about 500 to about 50,000 ppm. ### Claim 3 (depends on 2) The analyzer as defined in claim 2 wherein said second analyte is nitrogen having a concentration of from about 0.05 ppm to about 3,500 ppm. ### Claim 4 An analyzer for the determination of the concentration of first and second analytes in a sample comprising: a furnace for combusting a sample into gaseous byproducts of combustion; a source of an inert carrier gas for sweeping the byproducts of combustion from said furnace to a detector for the detection of a first analyte; a scrubber coupled to the detector for removing the first analyte from the inert gas stream; a second detector coupled to the scrubber for detecting the second analyte; a conduit coupled from said source of carrier gas to the junction of said scrubber and second detector; a control valve coupled in said conduit between said source and said second detector; a flow meter coupled in said conduit between said scrubber and said second detector; and a control circuit coupled to said flow meter for detecting the flow rate in said conduit and providing an output control signal applied to said control valve to maintain the flow rate in the flow path between said scrubber and said second detector substantially constant by controlling the flow of inert gas from said source when the scrubber tends to lower the flow rate due to relatively high concentrations of a first analyte as compared to the second analyte. ### Claim 5 (depends on 4) The analyzer as defined in claim 4 wherein said first analyte is oxygen having a concentration of from about 500 to about 50,000 ppm. ### Claim 6 (depends on 5) The analyzer as defined in claim 5 wherein said second analyte is nitrogen having a concentration of from about 0.05 ppm to about 3,500 ppm. ### Claim 7 A flow compensation system for an analyzer having an analytical furnace for the combustion and determination of the concentration of first and second analytes in a sample, comprising: a furnace for providing gaseous byproducts from a sample; first and second detectors for detecting the concentration of first and second analytes respectively, said detectors being connected in series to the outlet of said furnace; a source of an inert carrier gas and a first conduit for transferring the gaseous byproducts of combustion from said furnace to said detectors for detection of said first and second analytes, said first conduit extending between said detectors; a scrubber coupled to said first detector for removing selected gaseous products: wherein said second detector is coupled to said scrubber for detecting said second analyte; a second conduit coupled from said source of carrier gas to said first conduit extending between said detectors; a control valve coupled in said second conduit; a sensor coupled to said first conduit, said sensor located between said detectors; and a control circuit coupled to said sensor for detecting one of the pressure and flow rate in said first conduit and providing an output control signal applied to said control valve to maintain the flow substantially constant during an analysis of a sample having a relatively high concentration of a first analyte as compared to the second analyte. ### Claim 8 (depends on 7) The system as defined in claim 7 wherein said first analyte is oxygen having a concentration of from about 500 to about 50,000 ppm. ### Claim 9 (depends on 8) The system as defined in claim 8 wherein said second analyte is nitrogen having a concentration of from about 0.05 ppm to about 3,500 ppm. ### Claim 10 (depends on 7) The system as defined in claim 7 wherein said sensor is a pressure transducer coupled to said conduit. ### Claim 11 (depends on 7) The system as defined in claim 7 wherein said sensor is a flow meter coupled in said first conduit. ### Claim 12 (depends on 10) The system as defined in claim 10 wherein said first analyte is oxygen having a concentration of from about 500 to about 50,000 ppm. ### Claim 13 (depends on 12) The system as defined in claim 12 wherein said second analyte is nitrogen having a concentration of from about 0.05 ppm to about 3,500 ppm. ### Claim 14 (depends on 11) The system as defined in claim 11 wherein said first analyte is oxygen having a concentration of from about 500 to about 50,000 ppm. ### Claim 15 (depends on 14) The system as defined in claim 14 wherein said second analyte is nitrogen having a concentration of from about 0.05 ppm to about 3,500 ppm.