CHNS Analyzer, Combustion and Oxygen

LECO’s CHNS-932 Elemental Analyzer is capable of determining the amount of carbon, hydrogen, nitrogen and sulfur present in a homogeneous aliquot weighing approximately 0.6–1.6mg (2.0mg maximum). An aliquot is weighed and placed into either a tin or silver capsule in which it is appropriately crimped. During the analysis, the aliquot is dropped into a furnace held at 1,000°C. At the same time the sample drops into the furnace, a dose of oxygen is released into the furnace. This causes the sample to readily combust forming gases of COX, H2O, N2, and SOX. The instrument is able to indirectly detect the weight percent of C, H, N, and S by infrared detection of CO2, H2O, and SO2, and by thermal conductivity of N2. For accurate and reliable results materials must be homogenous and readily combust below 1000°C.

The VTF-900 is used in conjunction with the CHNS-932 for determination of oxygen weight percent. The VTF-900 uses high temperature pyrolysis (1,300°C) in order to remove the oxygen from the material. The oxygen is then converted to CO and finally CO2 before entering the carbon detection system.