Total Organic Carbon is often used as a screening parameter for organic matter in all kinds of water samples, including ground water, surface water and waste water. These samples sometimes contain substantial amounts of insoluble particles such as sediments, which must be included in the TOC analysis. The international standards EN 1484 (Annex A) and ISO 8245 (Annex B) provide a test method to verify the homogenization and recovery of incompletely dissolved sample components (particulate matter max. 100 μm) in TOC samples, also known as the ‘cellulose test’.
The suspension is prepared by placing 225 mg of cellulose (C6H10O5) with particles sizes ranging from 20 µm up to 100 µm in 1 liter of water with a concentration of 100 mg/L carbon. The samples should be continuously stirred during analysis. This is often done through magnetic stirrers in the auto sampler of a TOC analyzer to ensure the sample is homogeneous before analysis. The mean value from a triple measurement should be between 90 mg/L and 100 mg/L, the repeatability variation coefficient should be below 10% (RSD).