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Fully automated, high‐throughput instrumentation for measuring the δ 13 C value of methane and application of the instrumentation to rice paddy samples
Author(s) -
Tokida Takeshi,
Nakajima Yasuhiro,
Hayashi Kentaro,
Usui Yasuhiro,
Katayanagi Nobuko,
Kajiura Masako,
Nakamura Hirofumi,
Hasegawa Toshihiro
Publication year - 2014
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.7016
Subject(s) - chemistry , isotope ratio mass spectrometry , methane , instrumentation (computer programming) , analytical chemistry (journal) , throughput , reproducibility , stable isotope ratio , mass spectrometry , environmental chemistry , chromatography , telecommunications , physics , organic chemistry , quantum mechanics , computer science , wireless , operating system
RATIONALE The stable carbon isotope ratio ( 13 C/ 12 C or δ 13 C value) of methane (CH 4 ) produced in methanogenic environments contains information about primary source material, CH 4 production pathways, degree of oxidation, and transport. However, the availability of δ 13 C‐CH 4 data is severely limited because isotope analysis methods are low throughput, owing primarily to the need for manual processing steps. High‐throughput, fully automated measurement is necessary to facilitate the use of the δ 13 C signature in understanding CH 4 biogeochemistry. METHODS We modified a conventional continuous‐flow (CF) gas chromatography/combustion/isotope ratio mass spectrometry (IRMS) instrument system by incorporating (i) automated sample injection, (ii) a newly developed temperature‐control unit for preconcentration and cryofocus traps, and (iii) an automatic system for liquid‐nitrogen refilling. The system, which could run unattended for 1 day, was used to obtain δ 13 C‐CH 4 data for CH 4 samples collected from an irrigated rice paddy with an automated closed‐chamber system. RESULTS Using the fully automated CF‐IRMS system, we measured δ 13 C‐CH 4 data for 77 samples during a 21.5‐h continuous run (17 min per sample) with high precision (1σ = 0.11‰, reproducibility) and moderate consumption of liquid nitrogen (11 L). Application of the system to CH 4 samples obtained from the rice paddy revealed distinct seasonal and diurnal variations in δ 13 C values with the highest temporal resolution ever reported. CONCLUSIONS A fully automated, high‐throughput system for the measurement of δ 13 C‐CH 4 values was developed and used to analyze air samples obtained from a rice paddy. Our results demonstrate the high potential of this system for obtaining δ 13 C data useful for process‐level understanding of CH 4 biogeochemistry with respect to spatiotemporal variation of CH 4 sources and how that variation is affected by environmental and management factors. Copyright © 2014 John Wiley & Sons, Ltd.