The technique used is based on the well-known process of Flash Dynamic Combustion. Accurately weighed samples of approximately 1mg (to 3 decimal places in the mg range) in a lightweight tin capsule are dropped at preset intervals of time into a vertical quartz combustion tube maintained at 1020 deg.C, through which a constant flow of helium is run. When the sample is introduced, the helium stream is temporarily enriched with pure oxygen. Flash combustion takes place, primed by the oxidation of the tin container. Quantitative combustion is then achieved by passing the mixture of gases over tungstic oxide. The mixture of gases is then passed over copper to remove the excess of oxygen and reduce oxides of nitrogen to nitrogen. It then passes through a chromatographic column onto a TC detector. The gases eluted are N2 , CO2 , H2O, SO2. Suitable for organic or inorganic samples.
O is determined by weighing the sample into a silver capsule and heated to 1060 deg.C. It is quantitatively converted to CO by passing over nickel coated carbon.
Many materials are very often unhomogeneous, and an appropriate homogenisation procedure is therefore required. Important: the reproducibility of results is independent of the sample size but strongly dependent of the sample homogenity.