COMBUSTION TUBE METHOD FOR MEASUREMENT OF NITROGEN ISOTOPE RATIOS USING CALCIUM-OXIDE FOR TOTAL REMOVAL OF CARBON-DIOXIDE AND WATER

The nitrogen Isotope ratios of several organic and Inorganic materials have been analyzed by a sealed-tube combustion method requiring on-line cryogenic purification and by a new sealed-tube combustion technique using CaO for the quantitative removal of CO2 and water. Samples purified cryogenically are enriched In 15 N by an average of 0.11‰ relative to samples prepared with CaO. The enriched values of samples purified cryogenically probably result from the larger amounts of residual contaminants In samples prepared without CaO. Because samples prepared with the CaO technique require no additional purification, the technique is ideal for use with multisample mass spectrometer Inlet systems. © 1990, American Chemical Society. All rights reserved.