AUTOMATED-ANALYSIS SYSTEM FOR COUPLED DELTA-C-13 AND DELTA-N-15 MEASUREMENTS

A newly developed machine can analyze > 30 samples/day for stable isotopic composition, obtaining both delta-C-13 and delta-N-15 values from each sample. Samples are combusted to carbon dioxide and nitrogen gas in an elemental analyzer, cryogenically purified in a custom-built stainless steel manifold, and analyzed with an isotope ratio mass spectrometer. Analysis of standard reference materials (SRMs) distributed by the U.S. National Bureau of Standards showed that the automated system can produce good quality isotopic measurements from representative plant, animal, and sediment samples and that SRMs can be suitable isotopic reference materials for work with complex organic materials.