Absolute Calibration of the Intramolecular Site Preference of 15N Fractionation in Tropospheric N2O by FT-IR Spectroscopy
Absolute Calibration of the Intramolecular Site Preference of 15N Fractionation in Tropospheric N2O by FT-IR Spectroscopy
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DOI：
10.1021/ac802371c
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发表时间：
2009-03-15
影响因子：
7.4
通讯作者：
Wilson, Stephen R.
中科院分区：
文献类型：
--
作者：
Griffith, David W. T.;Parkes, Stephen D.;Wilson, Stephen R.
一氧化二氮（N2 O）作为温室气体和平流层臭氧消耗在大气化学中起着重要作用。N2 O的同位素测量为了解其大气源和汇提供了宝贵的见解。N-15在中心位置和末端位置之间分馏的偏好（“位点偏好”）是特别有价值的，因为它主要取决于N2 O产生或消耗中涉及的过程，而不是形成它的底物的N-15含量。尽管测量的网站偏好的价值，有没有国际公认的标准参考材料准确地知道和接受的网站偏好，并已发表的研究，旨在提供这样一个标准，一直缺乏一些协议。以前的工作一直是基于同位素比质谱（IRMS），在这项工作中，我们提供了一个绝对校准的分子内的位置偏好的N-15分馏的工作标准气体在我们的实验室中使用的一个完全独立的技术-高分辨率傅里叶变换红外（FT-IR）光谱。通过参考这个绝对校准，我们确定了在清洁空气条件下收集的对流层N2 O的25个样本的站点偏好为千分之19.8 +/-千分之2.1。这一结果与Toyoda和Yoshida（Toyoda，S.; Yoshida，N. Anal. 1999，71，4711-4718），他们发现了18.7份/千+/-2.2份/千的平均对流层位置偏好。我们现在建议将实验室间交换工作标准N2 O气体作为提供国际参考标准的下一步。
Nitrous oxide (N2O) plays important roles in atmospheric chemistry both as a greenhouse gas and in stratospheric ozone depletion. Isotopic measurements of N2O have provided an invaluable insight into understanding its atmospheric sources and sinks. The preference for N-15 fractionation between the central and terminal positions (the "site preference") is particularly valuable because it depends principally on the processes involved in N2O production or consumption, rather than the N-15 content of the substrate from which it is formed. Despite the value of measurements of the site preference, there is no internationally recognized standard reference material of accurately known and accepted site preference, and there has been some lack of agreement in published studies aimed at providing such a standard. Previous work has been based on isotope ratio mass spectrometry (IRMS); in this work we provide an absolute calibration for the intramolecular site preference of N-15 fractionation of working standard gases used in our laboratory by a completely independent technique-high-resolution Fourier transform infrared (FT-IR) spectroscopy. By reference to this absolute calibration, we determine the site preference for 25 samples of tropospheric N2O collected under clean air conditions to be 19.8 parts per thousand +/- 2.1 parts per thousand. This result is in agreement with that based on the earlier absolute calibration of Toyoda and Yoshida (Toyoda, S.; Yoshida, N. Anal. Chem. 1999, 71, 4711-4718) who found an average tropospheric site preference of 18.7 parts per thousand +/- 2.2 parts per thousand. We now recommend an interlaboratory exchange of working standard N2O gases as the next step to providing an international reference standard.