Chimuka L, Nemutandani T, Cukrowska E, Tutu H
School of Chemistry, University of the Witwatersrand, Johannesburg, 2050, South Africa.
J Environ Monit. 2008 Jan;10(1):129-35. doi: 10.1039/b713072d. Epub 2007 Oct 31.
A thin-walled silicone rubber hollow fibre membrane has been developed as a passive sampler. The inside of the tube is filled with an aqueous solution at an appropriate pH. The tube is sealed at both ends and then immersed in a water sample. In order for the ionizable permeating compounds to be trapped in the aqueous receiving phase, the pH is adjusted such that the compounds are ionized and trapped. The major advantages are its simplicity, low cost and high selectivity, since only ionizable organic compounds are trapped. Additionally, the sampler uses no organic solvent. By adjusting the pH of the acceptor phase, it is possible to control the extraction process and whether the sampler is used in the kinetic or equilibrium regime. Since it is very selective, no further clean-up of the extract is required. The membrane assisted passive sampler has been tested for extraction of chlorophenols under laboratory conditions. The extraction process was found to be linear over a 72 h sampling period. Selectivity of the passive sampler in river water was demonstrated and the extraction process was independent of sample concentration, even at lower concentration levels of analytes. However, the sample matrix in some river water samples led to incomplete trapping, thereby reducing the amount trapped in the acceptor phase. Detection limits (three times signal to noise ratio) were dependant on sample matrix and type of detection system and ranged from 0.05 microg L(-1) to about 1 microg L(-1) with a UV photodiode detector in water samples from one river and 1.0 microg L(-1) to 20 microg L(-1) in another but with an ordinary UV detector. The enrichment factors in river water were 28 for 2-chlorophenol and 44 for 2,4-dichlorophenol over a 72 h sampling period. 4-chlorophenol was poorly extracted and its enrichment factor was 3.
一种薄壁硅橡胶中空纤维膜已被开发用作被动采样器。管内填充有适当pH值的水溶液。管子两端密封，然后浸入水样中。为了使可电离的渗透化合物被捕集在水接收相中，调节pH值以使化合物电离并被捕集。其主要优点是简单、成本低和选择性高，因为只有可电离的有机化合物被捕集。此外，该采样器不使用有机溶剂。通过调节接受相的pH值，可以控制萃取过程以及采样器是用于动力学还是平衡模式。由于其选择性很高，因此无需对萃取物进行进一步净化。已在实验室条件下对膜辅助被动采样器进行了氯酚萃取测试。发现在72小时的采样期内萃取过程呈线性。证明了被动采样器在河水中的选择性，并且萃取过程与样品浓度无关，即使在分析物浓度较低的水平也是如此。然而，一些河水样品中的样品基质导致捕集不完全，从而减少了在接受相中捕集的量。检测限（信噪比的三倍）取决于样品基质和检测系统类型，在一条河流的水样中，使用紫外光电二极管检测器时，检测限范围为0.05 μg L-1至约1 μg L-1，而在另一条河流中使用普通紫外检测器时，检测限为1.0 μg L-1至20 μg L-1。在72小时的采样期内，河水中2-氯酚的富集因子为28，2,4-二氯酚的富集因子为44。4-氯酚的萃取效果较差，其富集因子为3。
