Relevant issues of determining total organic carbon in water

Abstract

Introduction. Total organic carbon (TOC) is a generalized indicator characterizing the pollution of water bodies with organic substances. In accordance with SanPiN 2.1.3864-21 for drinking water, the standard value of TOC content is set equal to 5 mg/dm3. Currently, total carbon analyzers are widely used to determine TOC. Despite its undoubted advantages, the determination of TOC on analyzers has many bottlenecks. Purpose of the study. Analysis of the TOC values of water samples of various origins, obtained using different methods and measurement conditions. Materials and methods. Determination of TOC was carried out with a total carbon analyzer TOC-VCHP (Shimadzu) in accordance with the operation manual of the difference measurement method (TOC) and non-blown organic carbon (NPOC). The objects of study were the water of natural sources, the centralized water supply system of various districts of Moscow, standard solutions of organic compounds. Results. It has been established that during the operation of the analyzer in the analysis of natural and drinking water, incomplete disclosure of humic and fulvic compounds is observed, which cannot be established by standard tests provided for carbon analyzers. The lack of standardized procedures for degassing sparkling water can lead to TOC errors of thousands of percent. Limitation. The limit of determined TOC values was 0.5 mg/dm3. Conclusion. To control the correctness of the determination of TOC in drinking, natural and waste waters, standard samples of humic compounds are required that are characteristic of a particular area with a certified TOC value. It is required to develop and implement a standard procedure for degassing gaseous samples when determining TOC, since the lack of control of this stage of analysis can lead to unacceptable errors in the determination.