Sieg Karsten, Fries Elke, Püttmann Wilhelm
Institute of Atmospheric and Environmental Sciences, Department of Analytical Environmental Chemistry, Johann Wolfgang Goethe-University Frankfurt/Main, Altenhöferallee 1, 60438 Frankfurt am Main, Germany.
J Chromatogr A. 2008 Jan 18;1178(1-2):178-86. doi: 10.1016/j.chroma.2007.11.025. Epub 2007 Nov 17.
The present study describes a method based on headspace-solid-phase dynamic extraction (HS-SPDE) followed by GC/MS for the qualitative and quantitative analysis of benzene, toluene, ethylbenzene, o-, m- and p-xylene (BTEX), and n-aldehydes (C(6)-C(10)) in water. To enhance the extraction capability of the HS-SPDE a new cooling device was tested that controls the temperature of the SPDE needle during extraction. Extraction and desorption parameters such as the number of extraction cycles, extraction temperature, desorption volume and desorption flow rate have been optimized. Detection limits for BTEX ranged from 19 ng/L (benzene) to 30 ng/L (m/p-xylene), while those for n-aldehydes ranged from 21 ng/L (n-heptanal) to 63 ng/L (n-hexanal). At a concentration level of 2 microg/L, the relative standard deviations (RSDs) for BTEX ranged from 3.9% (benzene) to 15.3% (ethylbenzene), while RSDs for n-aldehydes were between 6.1% (n-octanal) and 16.5% (n-hexanal) (n=7). Best results were obtained when the analyzed water samples were heated to 50 degrees C. At a water temperature of 70 degrees C GC responses decreased for all analyzed compounds. At a defined water temperature, a significant improvement of the GC response was achieved by cooling of the SPDE fiber during water extraction in comparison to an extraction keeping the fiber at room temperature. Evaluating the extraction cycles, for BTEX, the sensitivity was almost similar using 20, 40 and 60 extraction cycles. In contrast, the highest GC responses for n-aldehydes were achieved by the use of 60 extraction cycles. Optimizing the desorption parameters, best results were achieved using the smallest technical available desorption volume of 500 microL and the highest technical desorption flow rate of 50 microL/s. The method was applied to the analysis of melted snow samples taken from the Jungfraujoch, Switzerland (3580 m asl), revealing the presence of BTEX and aldehydes in snow.
本研究描述了一种基于顶空-固相动态萃取（HS-SPDE）并结合气相色谱/质谱（GC/MS）的方法，用于定性和定量分析水中的苯、甲苯、乙苯、邻二甲苯、间二甲苯和对二甲苯（BTEX）以及正构醛（C(6)-C(10)）。为提高HS-SPDE的萃取能力，测试了一种新的冷却装置，该装置在萃取过程中可控制SPDE针的温度。对萃取和解吸参数，如萃取循环次数、萃取温度、解吸体积和解吸流速进行了优化。BTEX的检测限范围为19 ng/L（苯）至30 ng/L（间/对二甲苯），而正构醛的检测限范围为21 ng/L（正庚醛）至63 ng/L（正己醛）。在浓度水平为2 μg/L时，BTEX的相对标准偏差（RSD）范围为3.9%（苯）至15.3%（乙苯），而正构醛的RSD在6.1%（正辛醛）至16.5%（正己醛）之间（n = 7）。当分析的水样加热到50℃时可获得最佳结果。在水温为70℃时，所有分析化合物的GC响应均下降。在规定的水温下，与在室温下保持纤维的萃取相比，在水萃取过程中冷却SPDE纤维可显著提高GC响应。评估萃取循环次数时，对于BTEX，使用20、40和60次萃取循环时灵敏度几乎相似。相比之下，使用60次萃取循环可获得正构醛的最高GC响应。优化解吸参数时，使用最小可用技术解吸体积500 μL和最高技术解吸流速50 μL/s可获得最佳结果。该方法应用于分析从瑞士少女峰（海拔3580 m）采集的融雪样品，结果显示雪中存在BTEX和醛类物质。
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