Direct and Indirect TOC Determination from Solids 

The Multi N/C series of catalytic combustion analysers from Analytik Jena (UK) provide a versatile platform that can be configured for the fully automatic direct determination of bound carbon (TIC/TOC, TC, NPOC, POC) from solid samples. Direct measurement of solids is made possible through the addition of the HT 1300 high-temperature solids combustion system, to fully meet the requirements of EN 13137 and EN 15936 for TOC measurement in waste soil and sediments.

The HT 1300 solids module is fully compatible with the Multi N/C 2100, Multi N/C 3100 and Multi N/C UV HS. It provides catalyst-free high temperature combustion in a robust ceramic combustion tube using an additional furnace which is adjustable up to 1,300 °C. The ceramic furnace tube can be used with all sample matrices including soil samples with high acidity or alkalinity, unlike quartz tubes which devitrify in the presence of HCl or samples with a high alkali content.

Large solid samples of up to 3 g can be accommodated, which allows for solids with low homogeneity. The large dynamic measuring range of the N/C range is particularly suited for the detection of high TOC content (up to 500 mg C absolute) in solids.

The HT 1300 can be used for either direct or indirect measurement of TOC in solids. The direct method is the recommended procedure for samples such as limestone that have a very high TIC content. The sample is first heated in acid to liberate TIC. The remaining solid is then transferred to the HT 1300 for rapid TOC measurement with a sample throughput of 2-3 minutes. If required, the system can also be used to measure TOC by the difference method, where 2 separate measurements are required to measure total carbon and inorganic carbon to allow TOC to be calculated by difference.

High accuracy results are ensured using patented VITA technology, which automatically determines the retention time of the sample in the analyser. This not only leads to good accuracy and sensitivity but also excellent repeatability. In addition, VITA significantly reduces the intervals between calibrations to around 6 months, reducing running costs. Multi N/C series instruments can be calibrated across the entire detection range using a single standard sample, eliminating the need for a large number of standard reference materials.