Direct Compound-Specific Stable Chlorine Isotope Analysis of Organic Compounds with Quadrupole GC/MS Using Standard Isotope Bracketing
Direct Compound-Specific Stable Chlorine Isotope Analysis of Organic Compounds with Quadrupole GC/MS Using Standard Isotope Bracketing
复制标题
DOI：
10.1021/ac902445f
复制
发表时间：
2010-01-01
影响因子：
7.4
通讯作者：
Gustafsson, Orjan
中科院分区：
文献类型：
--
作者：
Aeppli, Christoph;Holmstrand, Henry;Gustafsson, Orjan
开发了一种直接测定有机氯的稳定氯同位素组成（δ Cl-37）的方法，该方法无需样品制备，在提高灵敏度的同时实现了与早期技术相当的精度，并利用台式气相色谱-四极杆质谱仪（GCqMS）。该方法是基于使用多次进样（n = 8-10）的样品，括号内的分子相同的同位素标准与已知的δ Cl-37，使用离线热电离质谱法（TIMS）确定。两种同位素体的质量迹线相差一种氯同位素，用于计算δ Cl-37值。使用四氯乙烯（PCE）、p，p '-二氯二苯三氯乙烷（DDT）和五氯苯酚（PCP）实现了质谱和峰积分参数的优化以及方法验证，相对于SMOC，δ Cl-37范围为-5.5至+3.2 ppm。注射1.6-1100 pmol导致0.6-1.3 ppm的标准偏差（1 σ），并且Δ Cl-37结果与用TIMS独立测量的值一致。该方法进行了测试，通过确定纯液体PCE蒸发过程中的瑞利分馏，导致氯同位素富集因子的氯（Cl）= -1.1 +/- 0.4千分之一。此外，还评价了基于DDT质量碎片分析的位置特异性δ Cl-37分析。GCqMS-delta Cl-37方法为化合物特定的氯同位素分析提供了一种简化但灵敏的方法。
A method has been developed for the direct determination of the stable chlorine isotope composition (delta Cl-37) of organochlorines that eliminates sample preparation, achieves precision comparable to earlier techniques while improving the sensitivity, and makes use of benchtop gas chromatography-quadrupole mass spectrometry instruments (GCqMS). The method is based on the use of multiple injections (n = 8-10) of the sample, bracketed by a molecularly identical isotopic standard with known delta Cl-37, determined using off-line thermal ionization mass spectrometry (TIMS). Mass traces of two isotopologues differing by one chlorine isotope were used to calculate delta Cl-37 values. Optimization of mass spectrometry and peak integration parameters as well as method validation was achieved using tetrachloroethene (PCE), p,p'-dichlorodiphenyl-trichloroethane (DDT), and pentachlorophenol (PCP),spanning a delta Cl-37 range of -5.5 to +3.2 parts per thousand vs SMOC. Injecting 1.6-1100 pmol resulted in standard deviations (1 sigma) of 0.6-1.3 parts per thousand, and the delta Cl-37 results agreed with values independently measured with TIMS. The method was tested by determining the Rayleigh fractionation during evaporation of pure liquid PCE, resulting in a chlorine isotopic enrichment factor of epsilon(Cl) = -1.1 +/- 0.4 parts per thousand. Furthermore, position-specific delta Cl-37 analysis based on analysis of DDT mass fragments was evaluated. The GCqMS-delta Cl-37 method offers a simplified yet sensitive approach for compound-specific chlorine isotope analysis.