Combined 13C and 15N isotope analysis on small samples using a near-conventional elemental analyzer/isotope ratio mass spectrometer setup

RATIONALE A high sensitivity elemental analyzer/isotope ratio mass spectrometer setup was developed to allow analysis of C-13 and N-15 isotopic composition on microgram amounts of C and N, respectively. METHODS Increased sensitivity of a conventional elemental analyzer equipped with a low blank autosampler was obtained by decreased carrier gas flow of 35 mL/min. The diameters of the oxidation and reduction reactors and water trap were reduced to 7.8, 7.8 and 4 mm i.d., respectively, to obtain sharp sample peaks in the mass spectrometer. To increase the lifetime of the reduction reactor, a 1:1 He/O-2 mixture was used as oxidizing agent in the elemental analyzer. RESULTS Sample amounts of 0.6 mu g N and 1 mu g C were sufficient for accurate isotopic analysis with CONCLUSIONS The proposed setup proved to be suitable to analyze minute amounts of C and N in one analytical run simultaneously. Copyright (c) 2014 John Wiley & Sons, Ltd.