Analysator von Isotopenzusammensetzungen.

摘要

The invention comprises an on-line mass spectrometric method and apparatus for the determination of the isotopic composition of at least oxygen, hydrogen and nitrogen in a compound or mixture of compounds. A mixture contained in syringe 6 is injected through injector 7 on a chromatographic column 1. Compounds eluting from the column 1 pass into a catalytic reactor 14 (typically a platinum/rhodium capillary tube containing elemental carbon and maintained at 1200 DEG C) and are decomposed to produce carbon monoxide, molecular nitrogen, and molecular hydrogen. These gases are analyzed by an isotope-ratio mass spectrometer 4 so that the isotopic composition of the oxygen, nitrogen and hydrogen comprised in the original compound can be determined. A second chromatographic column 24 may be provided to separate carbon monoxide and nitrogen before they are passed into the spectrometer 4, thereby allowing a low resolution spectrometer to be used for the analysis of both gases at m/e 28 daltons. When only nitrogen is to be determined, the second chromatographic column 24 may be replaced by a methanizer. An alternative embodiment for determination of carbon isotopic composition uses a reactor 14 containing an oxygenated compound, e.g. water.