Departamento de Química, Universidade Federal de Santa Catarina, Florianópolis 88040900, SC, Brazil.
J Chromatogr A. 2012 Apr 13;1233:22-9. doi: 10.1016/j.chroma.2012.02.022. Epub 2012 Feb 17.
This study proposes a new optimization approach for the simultaneous determination of polycyclic aromatic hydrocarbons (PAHs) and benzene, toluene, ethylbenzene and xylene isomers (BTEX) from water samples using the solid-phase microextraction technique followed by gas chromatography-mass spectrometry (GC-MS) separation and detection. The objective of the study was to achieve compromise extraction conditions, suitable for all semi-volatile and volatile compounds, under which the amount extracted is maximized for all analytes. This was achieved by careful optimization of the fiber coating, salting-out effect, extraction time and temperature and extraction mode (headspace or direct immersion). With the optimized fiber coating - PDMS/DVB 65 μm - the other selected factors were optimized using a response surface methodology through central composite designs. As expected, the optimized results for each class of analytes varied significantly, probably due to the differences in their volatility and the equilibrium constants for the analyte/fiber coating. In order to overcome this issue, a new optimization approach was proposed based on a combination of extraction modes and extraction temperatures in a single extraction procedure. The final optimized procedure was: 48 min of extraction in direct immersion mode with the sample maintained at 80 °C followed by a further 32 min of headspace extraction with the sample temperature kept at 10 °C. The proposed procedure was compared with conventional methods based on the use of a single extraction mode and temperature (80 min of headspace extraction at 60 °C or 80 min of direct immersion extraction at 50 °C). The newly proposed method was shown to be more attractive as it extracted higher amounts of both semi-volatile and volatile compounds in a single extraction procedure compared to the conventional approaches. The optimized method was validated and excellent results were obtained.
本研究提出了一种新的优化方法，用于使用固相微萃取技术（SPME）结合气相色谱-质谱（GC-MS）分离和检测，同时从水样中测定多环芳烃（PAHs）和苯、甲苯、乙苯和二甲苯异构体（BTEX）。本研究的目的是在兼顾所有半挥发性和挥发性化合物的情况下，达到妥协的萃取条件，使所有分析物的萃取量最大化。这是通过仔细优化纤维涂层、盐析效应、萃取时间和温度以及萃取方式（顶空或直接浸入）来实现的。使用优化的纤维涂层（PDMS/DVB 65μm），通过中心复合设计对其他选定因素进行了响应面法优化。正如预期的那样，每种类别的分析物的优化结果差异显著，这可能是由于它们的挥发性和分析物/纤维涂层的平衡常数不同所致。为了克服这个问题，提出了一种新的优化方法，该方法基于在单个萃取过程中结合萃取方式和萃取温度。最终优化的程序为：在直接浸入模式下萃取 48 分钟，样品保持在 80°C，然后在 10°C 下进行进一步的 32 分钟顶空萃取。将所提出的程序与基于使用单一萃取模式和温度的常规方法（在 60°C 下进行 80 分钟的顶空萃取或在 50°C 下进行 80 分钟的直接浸入萃取）进行了比较。与传统方法相比，新提出的方法在单个萃取过程中提取了更多的半挥发性和挥发性化合物，因此更具吸引力。优化后的方法经过验证，结果非常理想。
