Determination of Total Organic Carbon and Organic Matter in Soil and Stream Sediment by High-Frequency Combustion-Infrared Absorption Spectrometry

The traditional potassium dichromate volumetric method has been difficult to meet the requirements of green environmental protection for determination of total organic carbon and organic matter in batch soil samples. In order to effectively improve detection efficiency and achieve the goal of using less or not using toxic and harmful reagents, the title method was proposed. 0.050 0 g of sample that had been roasted at 105 ℃ for 2 h was placed into a ceramic crucible that had been burned at 1 000 ℃ for 4 h, which was placed on a 85 ℃-constant temperature electric heating plate. The mixed solution of hydrochloric acid and water at volume ratio of 1∶5 was added dropwise until solution stopped bubbling. After evaporating to dryness, the sample was baked in a constant temperature drying oven at 105 ℃ for 2－3 h, and then taken out. 0.4 g of pure iron flux and 1.5 g of pure tungsten flux were added, in which total organic carbon and organic matter were determined by high-frequency combustion-infrared absorption spectrometry through high-carbon pool analysis gas path with analysis time of 30 s. It was shown that detection limit (3s) of total organic carbon was 0.012%, and detection limit (3s) of organic matter was 0.021%. Total organic carbon in 6 standard substances was determined, with RSDs (n=12) of the determined values less than 5.0%. The determined values were basically consistent with the certified values. This method was used to analyze 20 actual samples, and determination results were compared with those of traditional potassium dichromate volumetric method in NY/T 1121.6－2006. It was shown that determination results of two methods had good consistency.