| 摘要: |
| 本研究利用总有机碳分析仪联用稳定同位素质谱仪（TOC-IRMS）技术，探讨了高温氧化法测试水体中溶解有机碳（Dissolved Organic Carbon, DOC）含量及稳定碳同位素组成。根据溶解有机碳的组成特征，从氧化难易程度、分子结构等方面选取5种可溶于水的化合物：咖啡因、葡萄糖、邻苯二甲酸、乙酸钾和腐殖酸钠，配置成DOC溶液。通过改变溶液碳含量、氧化温度、通氧量大小，载气流速等参数，研究不同实验条件对DOC碳转化率及δ13C值的影响。TOC-IRMS在氧化温度850 ℃，通氧时长20 s（流速10 cm3/min），载气流速80 cm3/min的条件下，测得5种化合物不同浓度DOC溶液的平均碳转化率为95.69%~103.57%；δ13C值与标定参考值基本一致，差值范围为--0.82‰~0.55‰。在上述实验条件下，测得不同类型水样的DOC含量相对标准偏差小于3.7%，δ13C值的标准偏差小于0.2‰，结果表明TOC-IRMS联用在线高温氧化法测定不同类型水样的DOC含量和稳定碳同位素值满足测试精度要求。 |
| 关键词: 海洋化学 溶解有机碳（DOC） TOC-IRMS 高温氧化法 稳定碳同位素 |
| DOI：10.3969/J.ISSN.2095-4972.2023.02.016 |
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| 基金项目:自然资源部第三海洋研究所基本科研业务费专项（海三科2018004）；国家自然科学基金（42176057） |
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| On-line high temperature oxidation determination of stable carbon isotope composition of dissolved organic carbon by TOC-IRMS analysis |
| SU Rong,SHEN Kaiwen,YIN Xijie,YANG Haili |
| (Analysis and Test Center, Third Institute of Oceanography, MNR, Xiamen 361005, China) |
| Abstract: |
| In this paper, total organic carbon analyzer coupled with stable isotope mass spectrometer（TOC-IRMS）technology is used to study carbon isotope composition and dissolved organic carbon (DOC) in water using high temperature oxidation method. According to the composition characteristics of DOC, five water soluble compounds, namely caffeine, glucose, phthalic acid, potassium acetate and sodium humate, are selected from the aspects of oxidation in order of difficulty and molecular structure to prepare DOC solutions. By changing the experimental parameters, such as solution carbon concentration, oxidation tube temperature, oxygen admission time and carrier gas flow rate, the effect of different experimental conditions on the carbon conversion rate and isotope fractionation of five compounds are studied. The parameters of TOC-IRMS are set for oxidation temperature at 850 ℃, the oxygen supply time at 20 s (flow rate at 10 cm3/min), and the carrier gas flow rate at 80 cm3/min. The measured average carbon conversion rate of DOC solutions of five compounds in different concentrations is between 95.69%~103.57%, the δ13C are basically consistent with the calibration reference values, and the difference range is between －0.82‰~0.55‰. Under the experimental conditions, the relative standard deviation of DOC content in different types of water samples is less than 3.7%, the standard deviation of δ13C value is less than 0.2‰. Results show that the data obtained by TOC-IRMS online high-temperature oxidation method met the accuracy requirements. |
| Key words: marine chemistry dissolved organic carbon (DOC) TOC-IRMS high temperature oxidation stable carbon isotope composition |
