Effect Of Particulate Matter On Total Organic Carbon (TOC) Analysis Of Environmental Water Samples

Environmental and industrial laboratories use total organic carbon (TOC) as a tool to measure the organic pollutant loading of water samples. These samples are often turbid and contain varying amounts of particulate matter complicating both sampling and analysis. A difficulty in analyzing such samples is obtaining representative subsamples necessary for accurate and precise determinations of organic carbon. Futhermore acidification of samples, used to remove inorganic carbon, may result in the partial precipitation of humic acids producing negatively biased TOC results.

ASTM D 7573-09 Standard Test Method for Total Carbon and Organic Carbon in Water by High Temperature Catalytic Combustion and Infrared Detection recommends that samples containing high levels of particulate matter be filtered and both the liquid and solid fractions be analyzed for TOC content.(1) This application note reports TOC recoveries obtained on environmental water and runoff samples as separate dissolved organic carbon (DOC) and suspended organic carbon (SOC) fractions and as a total composite value. The effect of filtration and analysis of separate fractions on accuracy and precision is demonstrated.