Preparation of nanogram quantities of deuteromethane for stable carbon isotope analysis

Precise carbon isotope analysis at the nanogram level, using the static mass spectrometer, requires that sample carbon be in the form of deuteromethane. The authors describe the apparatus and technique for a low blank and quantitative deuteration reaction using a nickel catalyst for the conversion of carbon dioxide to deuteromethane. A regular relationship exists between the 12 C/ 13 C ratio for carbon dioxide measured conventionally at the microgram level and the m/z 20/21 ratio of CD 4 produced from 7-24*10 -9 g carbon aliquots of four samples of carbon dioxide whose carbon isotope compositions span most of the known natural abundance range.