Elemental Analysis Principles
The Elemental Analyzer uses flash (aka Dumas) combustion, (i.e., an exothermic reaction of tin at high temperature in the prescence of oxygen) to combust small samples of organic or inorganic material to produce carbon dioxide, nitrogen, sulfur, and hydrogen for analysis, either elemental or isotopic. The main components of elemental analysis for isotopic analysis include a oxidaton column, a reduction column, a water trap, a gas chromatographic column, and a gas interface.
The oxidation column is heated to ca. 1020°C and is composed of two reagents: Chromium Oxide (Cr2O3) situated in the middle of the column and Silvered Cobaltous/Cobaltic oxide situated towards the bottom of the coluumn and separated from the Cr2O3 by quartz wool. Chromium oxide serves as a secondary oxygen source to aid combustion, in addition to the introduced oxygen. The silver coating the cobaltous/cobaltic oxide reacts with sulfur bearing compounds, and the cobaltous/cobaltic oxide reacts with halides. Because tin reacts with quartz glass at high temperature it is necesary to add a liner between the quartz glass and combuste tin. At UCSC, we use shaped nickel foil to line the quartz tube.
Reaction products from the flash (Dumas) combustion include carbon dioxide (CO2), nitrogen (N2, oxides of nitrogen (NOx, N2O), and water (H2O). Furthermore, there is typically excess oxygen (O2) not consumed in the combustion of the sample.