A comparative analysis of two different analysers used for determination of the Total Organic Carbon in pharmaceutical grade water

Total Organic Carbon (TOC) is a routine test for pharmaceutical grade water. Several manufacturers supply equipment of different designs but there is a dearth of published, peer-reviewed, information evaluating the various analysers. In this study, we compared two TOC analysers, both validated to the same pharmacopoeial criteria, but with different oxidation and detection methods. The results in this paper show that there were no unexplained out-of-specification results and that both analysers operated equivalently in terms of the pharmacopoeial 500ppb pass/fail limits. However, significant differences between the TOC levels reported from paired samples were observed, two paired samples recorded a pass/fail conflict (albeit flagged with an overestimation warning), as well as differences in analyser responses between spiked samples that contained low levels of nitro- and chloro-carbon compounds.