Modification of Analytical Procedure for Determining Total Organic Carbon in Lake Waters Using a TOC Analyzer

Total organic carbon (TOC) is one of the indicators of organic pollution in aquatic environments. In this study, the pretreatment and measurement procedures employed when using a TOC analyzer with combustion catalytic oxidation are investigated to improve the accuracy of the analysis for samples containing suspended particles. Our results show that ultrasonically disrupting the particles promotes the homogenization of the suspension, which improves the accuracy of the TOC measurement. The TOC analyzer, which was designed to reduce the loss of samples in the injection syringe and the pathway of the equipment, obtained good recovery rates for samples taken from the north basin of Lake Biwa. However, low recovery rates were obtained for samples with high concentrations of suspended solids or dissolved organic matter. The low recovery rates reduced the accuracy of particulate organic carbon (POC) concentrations calculated as the difference between TOC and dissolved organic carbon (DOC) concentrations. It was found that the accuracy can be improved by using different methods (NPOC and TC-IC methods) for TOC combustion oxidation, depending on the sample concentration.