Determination of halogenated hydrocarbons by helium microwave plasma torch time-of-flight mass spectrometry coupled to gas chromatography.
Determination of halogenated hydrocarbons by helium microwave plasma torch time-of-flight mass spectrometry coupled to gas chromatography.
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DOI：
10.1021/ac970534r
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发表时间：
1998-08
影响因子：
7.4
通讯作者：
B. Pack;J. Broekaert;J. Guzowski;J. Poehlman;G. Hieftje
中科院分区：
文献类型：
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作者：
B. Pack;J. Broekaert;J. Guzowski;J. Poehlman;G. Hieftje
将氦微波等离子体炬（MPT）与飞行时间质谱（TOFMS）相结合，用于毛细管气相色谱（GC）分离的卤化烃检测。GC-MPT-TOFMS系统在整个实验过程中提供了良好的稳定性，避免了光谱偏斜引起的质谱峰畸变。在最初的研究中，利用流动电池装置预测了基于卤碳比的经验公式。MPT被证明非常坚固，可以处理大量的有机蒸汽。本研究结果表明，对于芳香族和脂肪族卤化烃，碳氯比值信号与它们的化学成分预期值具有良好的相关性（r = 0.994）。这项研究后来扩展到包括色谱分离。对于一系列同源的脂肪族卤化烃，其峰高和峰面积的相关系数均为0.999。为了保证毛细管柱从气相色谱炉加热到MPT，然后通过MPT的长度到达微波等离子体本身，开发了一种新型的镍铬丝加热传输线。热传输线没有明显的峰展宽和可检测的记忆效应。GC-MPT-TOFMS系统对I， Br和Cl具有相同的灵敏度。卤化烃的绝对检出限范围为160 - 330 fg，与先前使用TM010空腔支持的MIPs并结合四极杆质谱法获得的结果相比，提高了5-35倍。此外，还研究了分子气体对MPT性能的影响。在中央通道氦流中，高达1% （v/v）的氧或氢使碳和氯的信号水平都减弱，氯信号的损失更大。
A helium microwave plasma torch (MPT) was coupled to time-of-flight mass spectrometry (TOFMS) for the detection of halogenated hydrocarbons separated by capillary gas chromatography (GC). The GC-MPT-TOFMS system offered excellent stability over the course of the experiments and avoided mass spectral peak distortions caused by spectral skew. In the initial studies, empirical formulas based on the halogen-to-carbon ratio were predicted utilizing a flow cell apparatus. The MPT proved to be very robust and could handle large amounts of organic vapor. Results from this study indicate that, for both aromatic and aliphatic halogenated hydrocarbons, the ratios of carbon to chlorine signals correlate well (r = 0.994) with the ones expected from their chemical composition. This study was later extended to include chromatographic separation. For a series of homologous aliphatic halogenated hydrocarbons, a correlation coefficient of 0.999 was obtained for both peak heights and peak areas obtained from a single chromatogram. A novel Nichrome wire-heated transfer line was developed to ensure that the capillary column was heated efficiently from the GC oven to the MPT and then through the length of the MPT up to the microwave plasma itself. No appreciable peak broadening and no detectable memory effects were associated with the heated transfer line. The GC-MPT-TOFMS system offered equal sensitivity for I, Br, and Cl. Absolute detection limits for the halogenated hydrocarbons ranged from 160 to 330 fg, constituting an improvement by a factor of 5-35 over earlier results obtained with MIPs supported in a TM010 cavity and combined with quadrupole-based mass spectrometry. In addition, the effect of molecular gases on the MPT performance was investigated. Up to about 1% (v/v) of either oxygen or hydrogen in the central channel helium flow attenuated the signal levels for both carbon and chlorine, with the larger loss seen in the chlorine signal.