高温型酸化炉を用いるガスクロマトグラフィ/同位体比質量分析法によるアミノ酸の安定同位体比測定

抄録

Compound-specific stable isotope analysis (CSIA) of nitrogenous compounds has been carried out by using a gas chromatography/isotope ratio mass spectrometry (GC/IRMS) system, which traditionally includes two separate conversion processes: the oxidation of nitrogenous compounds to N₂ and NO_X; and the reduction of the NO_X to N₂. However, the last major update of the GC/IRMS instrument combined these two processes into one unit by introducing a high-temperature combustion reactor. However, few studies have evaluated the applicability of this new GC/IRMS system to measuring the nitrogen isotopic composition of compounds of interest. In the present study, we determined the nitrogen isotopic composition of ten amino acids by this new GC/IRMS system, and obtained the isotopic composition with 0.6‰ for accuracy (mean of Δ) and 1.2‰ for precision (mean of 1σ). These results suggest that the new GC/IRMS system is basically applicable to the CSIA of nitrogenous compounds, and also that further optimization is required for reducing the analytical error to that of the traditional GC/IRMS system (ca. 0.0‰ for accuracy and 0.4–0.7‰ for precision).