Non-purgable organic carbon is measured by acidifying samples to a pH less than 2.0 and sparging with CO2 free air. A combustion/non-dispersive infrared gas analysis method is employed. High purity carrier gas, moistened by a humidifier, flows at a rate of 150 mL/min. The sample is injected into a TC (Total Carbon) combustion tube, which has been filled with oxidation catalyst and heated to 680o C. The sample is combusted or decomposed to CO2. The combustion product is sent through an IC reaction vessel, cooled, dried by a dehumidifier and then sent through a halogen scrubber. The NPOC component is detected for CO2 in a non-dispersive infrared gas analyzer (NDIR). The peak area count is proportional to the NPOC concentration of the sample.