Total organic carbon analysis in water – A review of current methods

Total organic carbon (TOC) is a well-known and reliable parameter that acts as an indicator to estimate the amount of organic content in a water sample. Since the introduction of TOC analyzers in the 1960s, these devices have proven to be very critical in water quality assessment & process monitoring. The universal method is to measure TOC by oxidation of the organic content in the water sample to convert it into quantifiable forms. This article summarizes the commercially available methods of TOC analysis in water samples. The methods reviewed are combustion with non-dispersive infrared (NDIR) detection, catalytic oxidation with NDIR detection, persulphate oxidation and ultraviolet oxidation. We have highlighted the advantages of the various methods and their relative shortcomings. This study also compares the performance of the current TOC analyzers and TOC analysis of ultra-pure water that deserves specific attention as it contains organic carbon in trace levels. Based on the review, it is suggested that high-temperature combustion is quite an expensive oxidation method and is usually used for high-TOC water samples. Chemical-based oxidation (e.g., Persulphate) and UV oxidation methods provide reliable results in a lab for a wide range of water samples, including portable and ultra-pure water for semiconductor and pharmaceutical industries.