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Discussions about Total Organic Carbon

By: Danina Rinaldi

Testing bulk, sterile, purified, DI, or sterile water for pharmaceutical purposes is important for manufacturing, production and analytical applications.

Total organic carbon, or simply TOC, provides an indirect measurement of all the organic molecules in a water sample. The test method is very sensitive, providing results in ppb (parts per billion).  A major advantage to in using this test is that it accurately quantifies most organic materials that may be present in only trace amounts. Accordingly this methodology is well suited to verify cleaning in between manufacturing campaigns.

Because of its advantages TOC is one of the tests considered to be most critical for final water quality per the USP chapter <1231> Water for Pharmaceutical Purposes.   It is purposed to provide critical feedback to determine product quality and performance as well as immediate use and suitability.

In addition, there are many examples in the USP that require this test to be performed as a quality attribute. For example, Pure Steam, Water for Injection, Sterile Water for Inhalation, Sterile Water for Injection, Purified Water, Sterile Purified Water and Water for Hemodialysis.

Other USP general chapters containing requirement for this test to be performed  are <1051> Cleaning Glass Apparatus, <1059> Excipient Performance, <1661> Evaluation of Plastic Packaging Systems and their Materials of Construction with Respect to their User Safety Impact, <1663> Assessment of Extractables Associated with Pharmaceutical Packaging/Delivery Systems, <661.1> Plastic Materials of Construction and <661.2> Plastic Packaging Systems for Pharmaceutical Use.

When submitting samples, sponsors should be careful to note that the use of plastic materials may contribute to the TOC levels.  Other contaminating factors may be presence of alcohol or detergents and microbial contaminates.  The total organic carbon test is not a substitute for a routine microbiological monitoring practice.  To monitor the microbial quality of water a heterotrophic plate count and coliform tests are necessary to be performed.

Samples should be sent refrigerated, overnight in a 40 ml I-Chem Low Level Certified Vial.