Analytical procedure to determine both δ18O and δ17O of H2O2 in natural water and first measurements
Analytical procedure to determine both δ18O and δ17O of H2O2 in natural water and first measurements
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DOI：
10.1016/s1352-2310(99)00122-3
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发表时间：
1999-09
影响因子：
5
通讯作者：
J. Savarino;M. Thiemens
中科院分区：
文献类型：
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作者：
J. Savarino;M. Thiemens
本文介绍了一种同时测定天然水中过氧化氢（H_2O_2）δ ~（18）O和δ ~（17）O的实验方法。该测量的目的是更好地了解大气中过氧化物的化学转化。特别相关的是需要这些测量来解释在大气气溶胶硫酸盐中观察到的质量无关的同位素异常。结合过氧化物和硫酸盐同位素测量可能提供一种新的手段来解决大气氧化途径。该技术利用了众所周知的H2 O2与KMnO 4在硫酸溶液中的反应，该反应将H2 O2氧化为O2。通过氦气喷射、超声搅拌和泵送的组合对4升水样（1004升）进行脱气，以定量去除溶解在水中的空气。然后向溶液中加入KMnO 4，并回收氧化反应过程中产生的O 2。分子氧被捕获并在一系列分子筛中低温纯化，用于同位素测量。工业H_2O_2、H_2O_2氧化亚硫酸盐、H_2O_2的自分解和部分氧化等实验表明，这些样品都具有质量依赖性，并服从δ ~（17）O =0.511δ ~（18）O关系。雨水样品收集在拉霍亚，CA使用这种方法进行了分析。H_2O_2的分馏与质量无关，δ ~（18）O为21.9 ~ 52.5‰。我们认为，这一范围是由于亚硫酸盐在雨滴中的氧化和质量无关分馏的气相形成的H2 O2的结果。这是第一次在过氧化氢中观察到与质量无关的同位素组成。
An experimental technique has been developed to determine both δ18O and δ17O of hydrogen peroxide (H2O2) in natural water. The goal of this measurement is to develop a better understanding of peroxide chemical transformations in the atmosphere. Of particular relevance is the need for these measurements to interpret mass-independent isotopic anomalies observed in atmospheric aerosol sulfate. Combined peroxide and sulfate isotopic measurements may provide a new means to resolve atmospheric oxidative pathways. The technique utilizes the well-known reaction of H2O2with KMnO4in sulfuric acid solution, which oxidizes H2O2to O2. Four liters of water sample (∼4l) are degassed by a combination of helium sparging, ultrasonic agitation and pumping to quantitatively remove air dissolved in water. KMnO4is then added to the solution and O2produced during the oxidation reaction is recovered. Molecular oxygen is trapped and cryogenically purified in a series of molecular sieves for isotopic measurement. Industrially manufactured H2O2, sulfite oxidation by H2O2, auto-decomposition and partial oxidation of H2O2show that all these samples are mass dependent, and obey the relationship δ17O =0.511δ18O . Rainwater samples collected at La Jolla, CA were analyzed using this method. The H2O2is mass-independently fractionated and δ18O range from 21.9 to 52.5‰. We suggest that this range is due to the oxidation of sulfite in rain droplet and the mass-independent fractionation a result of gas-phase formation of H2O2. This is the first observation of a mass-independent isotopic composition in hydrogen peroxide.