Analyzing system for high accuracy nitrogen determination

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.

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.