Optimizing the removal of carbon phases in soils and sediments for sequential chemical extractions by coulometry

摘要: We have developed a coulometric technique to optimize the removal of carbonate and organic fractions for sequential chemical extractions soils sediments. The system facilitates optimizing these two by direct real-time measurement carbon dioxide (CO2) evolved during fractions. Further analyses ICP-MS alpha-spectrometry aided in interpreting results coulometry experiments. effects time, temperature, ionic strength pH were investigated. sensitivity reaction vessel/detection was sufficient even at very low total content (< 0.1 mol kg-1). efficiency is estimated be 96% with standard deviation 8%. Experiments carried out using NIST Standard Reference Materials 4357 Ocean Sediment (OS), 2704 Buffalo River (BRS), pure calcium carbonate. Carbonate minerals dissolved selectively an ammonium acetate-acetic acid buffer. Organic matter then oxidized CO2 hydrogen peroxide (H2O2) nitric acid. fraction completely within 120 min under all conditions examined (literature suggests up 8 h). For OS standard, oxidation self-perpetuates between 45 50 degrees C, factor less than commonly suggested, while BRS required 80 C proceed completion. complete matter, we find that least three additions H2O2 are (popular methods suggest one or two).