Simultaneous determination of δ15N and δ18O of N2O and δ13C of CH4 in nanomolar quantities from a single water sample
Simultaneous determination of δ15N and δ18O of N2O and δ13C of CH4 in nanomolar quantities from a single water sample
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DOI：
10.1002/rcm.4483
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发表时间：
2010-04-01
影响因子：
2
通讯作者：
Nakagawa, F.
中科院分区：
文献类型：
--
作者：
Hirota, A.;Tsunogai, U.;Nakagawa, F.
我们已经开发了一种快速，灵敏，自动化的分析系统，同时确定浓度和稳定的同位素组成（Δ N-15，Δ O-18，和Δ C-13）的纳摩尔量的一氧化二氮（N2 O）和甲烷（CH 4）在水中，通过结合连续流同位素比质谱和氦喷射系统提取和纯化溶解的气体。我们的系统，这是由冷阱和毛细管气相色谱仪，使用超纯氦气作为载气，实现了完全提取的N2 O和CH 4的水样和分离N2 O，CH 4，和其他成分的气体。周期性地改变从气相色谱仪出口之后的流路，使气体通过燃烧炉以将CH 4和其它烃转化为CO2，或者绕过燃烧炉以将洗脱的N2 O直接引入质谱仪，用于通过监测CO2+和N2 O+的m/z 44、45和46的离子来确定稳定同位素组成。该分析系统可以用在个人计算机上编程的顺序软件自动操作。当N_2O的进样量分别大于6.7 nmol和0.2 nmol时，N_2O的Δ N-15和Δ（18）0的分析精度分别优于0.2份/千和0.3份/千，优于1.4份/千和2.6份/千。同时，分析精度优于0.07%，和2.1份千分之时，获得的δ C-13的CH 4时，超过5.5 nmol和0.02 nmol的CH 4，分别注入。以这种方式，我们可以同时确定稳定的同位素组成的120毫升水样的浓度低至1.7 nmol/kg的N2 O和0.2 nmol/kg的CH 4。版权所有（C）2010约翰威利父子有限公司
We have developed a rapid, sensitive, and automated analytical system to simultaneously determine the concentrations and stable isotopic compositions (delta N-15, delta O-18, and delta C-13) of nanomolar quantities of nitrous oxide (N2O) and methane (CH4) in water, by combining continuous-flow isotope-ratio mass spectrometry and a helium-sparging system to extract and purify the dissolved gases. Our system, which is composed of cold traps and a capillary gas chromatograph that use ultra-pure helium as the carrier gas, achieves complete extraction of N2O and CH4 in a water sample and separation among N2O, CH4, and the other component gases. The flow path following exit from the gas chromatograph was periodically changed to pass the gases through the combustion furnace to convert CH4 and the other hydrocarbons into CO2, or to bypass the combustion furnace for the direct introduction of eluted N2O into the mass spectrometer, for determining the stable isotopic compositions through monitoring the ions of m/z 44, 45, and 46 of CO2+ and N2O+. The analytical system can be operated automatically with sequential software programmed on a personal computer. Analytical precisions better than 0.2 parts per thousand and 0.3 parts per thousand and better than 1.4 parts per thousand and 2.6 parts per thousand were obtained for the delta N-15 and delta(18)0 of N2O, respectively, when more than 6.7 nmol and 0.2 nmol of N2O, respectively, were injected. Simultaneously, analytical precisions better than 0.07%, and 2.1 parts per thousand were obtained for the delta C-13 of CH4 when more than 5.5 nmol and 0.02 nmol of CH4, respectively, were injected. In this manner, we can simultaneously determine stable isotopic compositions of a 120 mL water sample with concentrations as low as 1.7 nmol/kg for N2O and 0.2 nmol/kg for CH4. Copyright (C) 2010 John Wiley & Sons, Ltd.