Development of an acid extraction-NDIR method for the determination of total dissolved inorganic carbon using small sample volumes

The major parameters of the oceanic carbonate system include pH, total dissolved inorganic carbon (CT), total alkalinity, and fugacity of CO2. These parameters are important for measuring the effect of CO2 on the earth. This study developed a measurement system based on a nondispersive infrared method that can determine the CT with high precision using an extremely small sample. This is an improvement over previously developed system. The gas flow path and flow rate, opening/closing timing of the valve that switches the flow path, purge method, and CT calculation method were improved. The measurement only required a sample volume of 300 μL. A repeat analysis of the certified reference material (n = 8) showed that the relative standard deviation was ±0.85%. This study provides a highly accurate and precise analytical method for measuring carbonate species in coral reefs and mesocosm cultures.