Lankes Ulrich, Müller Margit B, Weber Matthias, Frimmel Fritz H
Engler-Bunte-Institut, Bereich Wasserchemie, Universität Karlsruhe (TH), 76128 Karlsruhe, Germany.
Water Res. 2009 Mar;43(4):915-24. doi: 10.1016/j.watres.2008.11.025. Epub 2008 Nov 30.
The evaluation of the molecular size distribution of natural organic matter (NOM) in aquatic environments via size exclusion chromatography (SEC) is important for the understanding of environmental processes such as nutrient cycling and pollutant transport as well as of technical water treatment processes. The use of organic carbon (OC) detectors has become popular in recent studies due to improved availability and quantification possibilities, which supposedly are superior to those of ultraviolet (UV) detectors. A set of 12 NOM samples was used to demonstrate the limitations of online OC detection (OCD) when analyzing complex aquatic organic matter. A novel evaluation approach for SEC data is introduced by combining the information from UV absorbance (UVA) and OCD chromatograms as well as offline total OC (t-OC) and dissolved OC-specific UVA (SUVA) measurements. It could be shown that about 70% of certain OC components were not detected with the OCD system used in this study. For the investigated samples, these types of carbon accounted for up to 72% of the t-OC, i.e. for such NOM samples quantification by OCD is not possible or at least highly questionable. The addition of an oxidant improved the overall oxidation efficiency only slightly. Most likely NOM that predominantly consists of polysaccharides and features a nominal molecular weight of 150kg/mol or more was responsible for low OCD yields. For future applications, a further improvement of the OCD system would be worthwhile so that quantitative analytical data on the molecular size distribution of NOM and its structural characteristics such as the SUVA distribution can be obtained.
通过尺寸排阻色谱法（SEC）评估水生环境中天然有机物（NOM）的分子大小分布，对于理解诸如营养物质循环和污染物迁移等环境过程以及技术水处理过程而言至关重要。由于有机碳（OC）检测器的可用性提高和定量可能性增强，近年来在研究中其使用已变得普遍，据推测其优于紫外（UV）检测器。使用一组12个NOM样品来证明在线OC检测（OCD）在分析复杂水生有机物时的局限性。通过结合紫外吸光度（UVA）和OCD色谱图以及离线总OC（t-OC）和特定于溶解OC的UVA（SUVA）测量的信息，引入了一种用于SEC数据的新型评估方法。结果表明，在本研究中使用的OCD系统未检测到约70%的某些OC组分。对于所研究的样品，这些类型的碳占t-OC的比例高达72%，即对于此类NOM样品，通过OCD进行定量是不可能的，或者至少是极不可靠的。添加氧化剂仅略微提高了整体氧化效率。最有可能的是，主要由多糖组成且标称分子量为150kg/mol或更高的NOM导致了OCD产率较低。对于未来的应用，值得进一步改进OCD系统，以便能够获得关于NOM分子大小分布及其结构特征（如SUVA分布）的定量分析数据。
