TOC analysis is a technique for measuring the total concentration of carbon from organic sources in water. For environmental processes, it is often used to assess the amount of organic impurities in public water sources to ensure safe levels.

Measurement of TOC requires the conversion of a sample’s carbonaceous material to carbon dioxide. Most analyzers use a nondispersive IR (NDIR) spectrometer to measure the gaseous carbon dioxide. To obtain TOC content, carbon from inorganic sources, such as carbonate ions, must first be separated from organic carbon.

TOC analyzers acidify the sample to convert the inorganic carbon to carbon dioxide, which can then be sparged with an inert gas for removal or analysis. One of the most common methods for analyzing the remaining sample is combustion oxidation, in which the sample is heated in a furnace to convert the remaining organic carbon into carbon dioxide. This method is generally used for samples that contain salt or are hard to oxidize.

Also common is the UV-persulfate method, in which the water is treated with a persulfate oxidant in the presence of UV light to oxidize the remaining carbon to carbon dioxide. This method is best used for moderate- or low-level TOC samples. TOC systems are sometimes equipped with optional total nitrogen (TN) analyzers.

Municipal wastewater facilities routinely use TOC to monitor the treatment of organic impurities in sewer water. Because the facilities often deal with high TOC levels, they generally use combustion-oxidation analyzers. Similarly, to comply with environmental regulations, industrial manufacturers that deal with chemicals must monitor their wastewater for unsafe levels of contaminants before it can be released into the municipal drainage system. TOC analysis is also used for potable- and surface-water monitoring, for which UV-persulfate analyzers are common.

Shimadzu, the leading supplier of TOC analyzers for environmental applications, offers a variety of methods and options, including the TOC-L series and TOC-4200 online system. GE Analytical Instruments is another major vendor, known for utilizing a supercritical water–oxidation technique in its Sievers InnovOx TOC analyzers. GE also developed the Sievers M5310C TOC analyzer series, which is designed for the municipal-water market to monitor raw- and finished-water TOC levels. Danaher’s Hach Ultra Analytics is known for its BioTector TOC analyzers for industrial environmental applications. Other significant vendors include Analytik Jena, Teledyne Tekmar and Thermo Fisher Scientific.

The total worldwide demand for TOC analyzers used for environmental applications, including both TOC and TOC/TN systems, is estimated at about $70 million in 2015. Increasingly strict environmental regulations are expected to drive market growth, particularly in developing regions. In developed countries, the market is dominated by replacement sales.

TOC Analysis at a Glance:

Leading Suppliers

• Shimadzu

• GE Analytical Instruments

• Hach (Danaher)

Largest Markets

• Industrial Effluent

• Municipal Wastewater

• Potable-Water Monitoring

Instrument Cost

• $10,000–$80,000