Aachener Verfahrenstechnik, Chemical Process Engineering, RWTH Aachen University, Turmstr. 46, 52064 Aachen, Germany.
Talanta. 2010 Jun 30;82(1):92-8. doi: 10.1016/j.talanta.2010.04.001. Epub 2010 Apr 9.
Landfill or digester gas can contain man-made volatile methylsiloxanes (VMS), usually in the range of a few milligrams per normal cubic metre (Nm(3)). Until now, no standard method for siloxane quantification exists and there is controversy with respect to which sampling procedure is most suitable. This paper presents an analytical and a sampling procedure for the quantification of common VMS in biogas via GC-MS and polyvinyl fluoride (Tedlar) bags. Two commercially available Tedlar bag models are studied. One is equipped with a polypropylene valve with integrated septum, the other with a dual port fitting made from stainless steel. Siloxane recovery in landfill gas samples is investigated as a function of storage time, temperature, surface-to-volume ratio and background gas. Recovery was found to depend on the type of fitting employed. The siloxanes sampled in the bag with the polypropylene valve show high and stable recovery, even after more than 30 days. Sufficiently low detection limits below 10 microg Nm(-3) and good reproducibility can be achieved. The method is therefore well applicable to biogas, greatly facilitating sampling in comparison with other common techniques involving siloxane enrichment using sorption media.
垃圾填埋场或消化器气可能含有人造挥发性甲基硅氧烷 (VMS)，通常每标准立方米 (Nm(3)) 的含量在几毫克范围内。到目前为止，还没有硅氧烷定量的标准方法，并且对于哪种采样程序最合适存在争议。本文通过气相色谱-质谱法和聚偏二氟乙烯 (Tedlar) 袋提出了一种用于通过 GC-MS 定量分析沼气中常见 VMS 的分析和采样程序。研究了两种市售的 Tedlar 袋模型。一种配备有带集成隔垫的聚丙烯阀，另一种配备有双端口配件，由不锈钢制成。研究了垃圾填埋场气体样品中硅氧烷的储存时间、温度、表面积与体积比和背景气体对储存时间的影响。发现回收率取决于所使用的配件类型。即使在 30 多天后，带有聚丙烯阀的袋子中采样的硅氧烷仍具有高且稳定的回收率。可以达到足够低的检测限低于 10 微克 Nm(-3) 和良好的重现性。因此，该方法非常适用于沼气，与其他涉及使用吸附介质富集硅氧烷的常见技术相比，大大简化了采样。
