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.