Chlorine Isotope Analysis of Organic Contaminants Using GC鈥搎MS: Method Optimization and Comparison of Different Evaluation Schemes

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• 作者：Biao Jin ; Christine Laskov ; Massimo Rolle ; Stefan B. Haderlein
• 刊名：Environmental Science & Technology
• 出版年：2011
• 出版时间：June 15, 2011
• 年：2011
• 卷：45
• 期：12
• 页码：5279-5286
• 全文大小：954K
• 年卷期：v.45,no.12(June 15, 2011)
• ISSN：1520-5851

文摘

Compound-specific online chlorine isotope analysis of chlorinated hydrocarbons was evaluated and validated using gas chromatography coupled to a regular quadrupole mass spectrometer (GC鈥搎MS). This technique avoids tedious off-line sample pretreatments, but requires mathematical data analysis to derive chlorine isotope ratios from mass spectra. We compared existing evaluation schemes to calculate chlorine isotope ratios with those that we modified or newly proposed. We also tested systematically important experimental procedures such as external vs. internal referencing schemes, and instrumental settings including split ratio, ionization energy, and dwell times. To this end, headspace samples of tetrachloroethene (PCE), trichloroethene (TCE), and cis-dichloroethene (cDCE) at aqueous concentrations in the range of 20鈥?00 渭g/L (amount on-column range: 3.2鈥?15 pmol) were analyzed using GC鈥搎MS. The results (³⁷Cl/³⁵Cl ratios) showed satisfying to good precisions with relative standard deviations (n = 5) between 0.4鈥?and 2.1鈥? However, we found that the achievable precision considerably varies depending on the applied data evaluation scheme, the instrumental settings, and the analyte. A systematic evaluation of these factors allowed us to optimize the GC鈥搎MS technique to determine chlorine isotope ratios of chlorinated organic contaminants.