736 Series Inert Gas Fusion

Oxygen and Nitrogen by Inert Gas Fusion

With our ON736 elemental analyzer, you can transform your Oxygen and Nitrogen determination in inorganic materials, ferrous and nonferrous alloys, and refractory materials. It has an intuitive touchscreen Cornerstone® software, a high-performance detector architecture, and a variety of optional, customizable features to provide the best solution for your lab.


  • High performance detector design
    • Thermostatic construction protects from ambient temperature fluctuations
    • Optimized emitter control and detection circuitry
  • Choice of either argon and helium carrier gas
  • Increase laboratory productivity with automation options
    • Available autocleaner minimizes the need for manual cleaning between analysis
    • 20-position shuttle loader for both crucibles and samples
  • Boom-mounted touch-screen interface provides improved ergonomics and intuitive operation
    State-of-the-art infrared (IR) detection for oxygen determination and thermal conductivity (TC) detection of nitrogen


Inorganic materials, ferrous and nonferrous alloys, copper, aluminium, and refractory materials are all good candidates for the 736 series.

Theory of Operation

The ON736 Oxygen/Nitrogen system was created to measure the oxygen and nitrogen content of steel and other inorganic materials at the same time. The instrument is equipped with bespoke software that is optimised for touch operation.

To liberate analyte gases, a pre-weighed sample is placed in a graphite crucible that is heated in an impulse furnace. CO and CO2 are formed when oxygen in the sample reacts with the graphite crucible. The freed gases are swept out of the furnace and through a Mass Flow Controller by an inert gas carrier, usually helium. The gas is then passed through a heated reagent, where the CO is converted to CO2 and the H2 is converted to H2O. A non-dispersive infrared (NDIR) cell is used to detect oxygen as CO2. After that, CO2 and H2O are cleansed. 

The carrier gas stream is then cleaned of CO2 and H2O. The leftover nitrogen is detected using a Thermal Conductivity (TC) detector.

Both NDIR and TC detectors are used in the detection system. The premise behind NDIR cells is that analyte gas molecules absorb infrared (IR) light at specific wavelengths across the IR spectrum. As the gases flow through the IR absorption cells, incident IR radiation at these wavelengths is absorbed. The differential in thermal conductivity between the carrier and analyte gases is used in TC detection. A bridge circuit heats resistive TC filaments that are positioned in a flowing stream of carrier gas.

The rate at which heat transfers from the filaments changes when analyte gas is injected into the carrier stream, causing a detectable deflection in the bridge circuit.

An unknown sample’s concentration is determined by comparing it to calibration standards. Prior to each study, reference measurements of pure carrier gas are taken to reduce interferences from instrument drift.