Methodological study demonstrates simultaneous isotopic analysis in microgram carbon and nitrogen samples, indicating an accessible pathway for high-sensitivity mass spectrometry.
RATIONALE: A high sensitivity elemental analyzer/isotope ratio mass spectrometer setup was developed to allow analysis of (13)C and (15)N 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/O2 mixture was used as oxidizing agent in the elemental analyzer. RESULTS: Sample amounts of 0.6 µg N and 1 µg C were sufficient for accurate isotopic analysis with <1 ‰ standard error after blank correction. One major advantage of the setup is the easy switching between conventional EA and μEA as only consumable parts need to be exchanged. CONCLUSIONS: The proposed setup proved to be suitable to analyze minute amounts of C and N in one analytical run simultaneously.
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Langel et al. (2014) studied this question.
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