Application Note: Total Organic Carbon Analysis Of Solid Samples For Environmental And Quality Control Applications

Total Organic Carbon (TOC) analysis of solid samples provides useful information for environmental applications including waste management, biomass conversion, and carbon cycle research. TOC analysis is also used to perform quality control (QC) checks on industrial materials such as fly ash, cement, and kaolin. The heterogeneous composition of environmental samples poses an analytical challenge. Analytical methods (SW 846 Method 9060A and ISO 10694:1995) (1,2) describe matrix conditioning steps (e.g., sample drying, grinding, and pre-acidification to remove inorganic carbon) that are often required to ensure complete oxidation of organic matter and an accurate TOC value is obtained.

Existing techniques for TOC analysis of solids introduce the sample into a furnace for combustion. The resulting combustion gases are swept by a carrier gas stream from the furnace directly into a detector for measurement of CO2 and calculation of the carbon content. This approach limits the sample mass that can be efficiently combusted and the measurable carbon range of samples. As a consequence, instruments operating on this principle are prone to over- and/or under-ranging the carbon content of materials being tested.

This application note details design and performance characteristics of a new sample preparation module for TOC analysis of solid samples that incorporates a gas sampling device to collect all CO2 gas from combustion of each sample prior to transfer of a gas aliquot for measurement. Analytical results obtained on three Standard Reference Materials (SRMs), and humic acid, fly ash, and cellulose samples are reported.