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TOC Analyzers

TOC Analyzers & the Benefits of Leasing

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TOC analyzer diagram

Since the Clean Water Act was passed in 1972, wastewater treatment processes have become increasingly strict, and for good reason.

Analytical diagram

Stringent requirements for water quality ultimately benefit manufacturers, consumers and the environment. However, maintaining clean water is an ongoing challenge as increasing populations and growing industries use more water and produce more wastewater. It makes improving the efficiency of removing byproducts and pollutants to meet established environmental regulatory limits that much more important and necessary.

Testing water purity, and maintaining water quality in general, is not only important for clean drinking water, but it also plays a big role in the pharmaceutical, semiconductor, and power industries’ manufacturing processes. If bacteria and other unintended organic compounds are present in the water, they can render the water useless or indicate that there is an issue with the filtration or storage system.

When ignored, this tainted water can be detrimental to whatever process it is a part of, even leading to breaks in various industrial equipment. This makes monitoring various impurities in water essential to commercial industries as well as public ones.

Total organic carbon (TOC) refers to the amount of carbon that is present in an organic compound. Measuring how much organic carbon is present in a substance also quantifies the amount of organic matter that is present. Though TOC is most often related to water analysis and water treatment, it can also refer to the amount of carbon present in soil and other geological formations. Simply put, TOC is used to track the change—or lack of change—of organic content within a sample.

While TOC is a fairly ubiquitous term for carbon analysis, there are more specific terms that are used depending on the type of carbon being measured, including:

  • Total Carbon (TC): The total of all carbon present in a sample.
  • Total Inorganic Carbon (TIC): Sometimes referred to as just inorganic carbon (IC), carbonate, bicarbonate, and dissolved carbon dioxide (CO2).
  • Elemental Carbon (EC): Depending on the method used, EC can be a subcategory of TIC or TOC. It is also known as black carbon depending on the measurement method used.
  • Non-Purgeable Organic Carbon (NPOC): Denotes the amount of organic carbon that remains after an acidified sample is purged with gas.
  • Purgeable (volatile) Organic Compound (VOC): Refers to the amount of organic carbon that is removed from a neutral or acidic sample with an inert gas.
  • Dissolved Organic Carbon (DOC): Indicates the amount of carbon that is in a sample after it is filtered.
  • Suspended Organic Carbon: Tracks the number of carbon particles that are too large to pass through a filter. This is also known as particulate organic carbon (POC).

As you can see, TOC analysis is performed in a variety of ways, some of which we will cover below.

TOC Analyzer Processes & Applications

Hand holding a data point

Total organic carbon analyzers are instruments that measure TOC concentration in a sample. Almost all of them track CO2 formation both when organic carbon is oxidized and when inorganic carbon is acidified.

The specifics of the oxidation and acidification will vary depending on the environment of the sample, the concentration of TOC, and the testing parameters. Oxidation can be achieved through multiple methods. Some examples include Pt-catalyzed combustion and UV/persulfate oxidation.

After oxidation has occurred, a detector, either a conductivity cell or a non-dispersive infrared cell, then measures the amount of CO2 that has formed. Detecting organic carbon through acidification occurs by first flushing the inorganic carbon out of the sample with either helium or nitrogen and then measuring the remaining organic carbons.

TOC analysers can be organized into one of two types: combustion analyzers and chemical oxidation analyzers.


TOC combustion analysis is done after half of the sample is put into a chamber where it is acidified and half is put into a combustion chamber. In the acidified solution, a detector can measure organic carbons due to a chemical reaction that converts all of the inorganic carbon into CO2.

In the combustion chamber, the temperature is raised to 600-700 °C and all of the carbon in the sample reacts with the ambient oxygen to form CO2. After it is cooled, a detector measures the organic carbon.

High-temperature combustion (HTC) total organic carbon analyzers are used to accurately measure carbon content in aqueous matrices down to the ppm (parts per million) or ppb (parts per billion) level. The design allows for the pairing of an autosampler and an injection system—it also allows increases ease of use for the end-user. By closing off the injection process to the atmosphere, precision is improved and the chances of contamination are reduced.

Another combustion technique used to measure TOC includes a method originally developed by Shimadzu called the 680°C combustion catalytic oxidation method, performed using their TOC-L Series analyzers. This method achieves total combustion of samples by heating them to 680° C in an oxygen rich environment inside of combustion tubes filled with a platinum catalyst. Because of the principles of oxidation, sample pre-treatment and post-treatment is not necessary.

Chemical Oxidation

IChemical oxidation of carbon in TOC analysis includes a few different approaches:

  • Photo-oxidation (ultraviolet light): Photo-oxidation using ultraviolet light (UV) is a reliable, low maintenance method of analyzing TOC in ultra-pure waters. The oxidizing agent, UV, is sufficient enough to oxidize the sample.
  • Ultraviolet/persulfate oxidation: UV/persulfate oxidation also relies on UV as an oxidizer, however, persulfate or a persulfate compound is also added to increase the oxidation power of the reaction. It is, like photo-oxidation, a sensitive and reliable method that can be used in a wide range of applications. One downside to this method is that inaccuracies can be created due to the addition of foreign substances into the analyte.
  • Thermochemical persulfate oxidation: Thermochemical persulfate oxidation is also known as heated persulfate, and it relies on the same reactions occuring in UV/persulfate oxidation, except that this method uses heat to magnify the power of the oxidizing agent.

Chemical oxidation is often used in combination with NDIR detectors, which can measure TOC from hundreds of ppm to single digit ppb.

Produced Water Treatment

Oil has been the most influential natural resource since the 19th century and it continues to be heavily relied upon by all nations around the world. Technologies that use oil have advanced, and, likewise, our ability to harvest and refine it has also improved drastically.

A byproduct of industrial oil refinement is 2.5 billion gallons of produced water every day. This produced water has been labeled by the Environmental Protection Agency as being too contaminated to be used for household or commercial use. There are methods for treating this water and decontaminating it, however, they are either prohibitively expensive, not wholly effective, or are too energy-intensive.

Researchers at Purdue University have developed a relatively inexpensive method to remove almost all traces of oil from produced water. The method employs using heated, activated charcoal foam to remove the oil from the water. The process is able to achieve a TOC of 7.5 milligrams per liter, which, per the EPA standards, means it is clean water. Effective, inexpensive, and requiring little energy, this method can save billions of gallons of water from becoming useless.

Process Water Treatment

Not to be confused with produced water, process water refers to the water used in a number of ways across industrial manufacturing and processes, as well as power generation and drug manufacturing in the pharmaceutical industry. It is recommended that engineers and scientists measure TOC in process water. Doing so helps organizations understand whether the water they are using is pure enough for their processes.

This is important because all water, no matter how pure, contains some carbon materials. Many of these materials are introduced into the water from the water source, or from materials and systems during purification and production. The presence of these materials in the water—in this case, organic or inorganic carbon—can suggest a failure in filtration, storage or other systems/components. If left unfiltered, these compounds can create difficult and costly challenges, from damaging expensive industrial system to negatively impacting product quality and threatening profitability.

Detecting the presence of these organic contaminants and measuring their total concentration can help not only help protect industries, but it can also help protect consumers and the environment.

We Offer Total Organic Carbon Instrument Leases to Fit Every Need

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