Department of Agronomy, Purdue University, 915 W State St, West Lafayette, IN 47907, United States.
Chemosphere. 2010 Nov;81(7):911-7. doi: 10.1016/j.chemosphere.2010.07.068.
The experimental approaches used in assessing the biodegradability of fluorotelomer-based surfactants and polymers have been under increasing scrutiny. These substances consist of an aliphatic or aromatic backbone linked to perfluoroethyl moieties by ester, ether or urethane linkages. These linkages when broken yield fluorotelomer alcohols (FTOHs), which are known to biotransform to a suite of polyfluorinated metabolites including perfluorinated carboxylic acids. Quantifying FTOH levels with minimal experimental artifacts is imperative in properly assessing the biotransformation potential and half-lives of fluorotelomer-based materials. We examined the potential for solvent-enhanced ester hydrolysis of fluorotelomer compounds with different hydrocarbon backbones including a monoester stearate (FTS), a citrate tri-ester (TBC), an acrylate (FTA), and a 2,4-toluenediamine urethane (FTU) in acetonitrile, methyl-t-butyl ether (MTBE), and ethyl acetate with live, autoclaved, 60Co-γ-irradiated, and heat-treated (400°C) soils. Substantial hydrolysis only occurred with FTS in live and γ-irradiated soils for which microbial enzymes are expected to be active, but not in autoclaved soils where enzymes are deactivated. Acetonitrile and methanol (solvents with higher dielectric constants) enhanced hydrolysis by an order of magnitude compared to less polar solvents such as MTBE and ethyl acetate. For example, in a 24-h extraction with acetonitrile of FTS-amended soil, >5wt.% FTOH was produced compared to <0.04wt.% in either ethyl acetate or MTBE. FTA hydrolysis was <0.7 wt.% after a 15-h extraction period and was not solvent dependent. No statistically significant solvent-enhanced hydrolysis was observed for TBC, FTA or FTU.
评估含氟表面活性剂和聚合物生物降解性所采用的实验方法正受到越来越多的关注。这些物质由脂肪族或芳香族主链组成，通过酯、醚或氨酯键与全氟乙基部分相连。这些键断裂后会生成氟调聚物醇（FTOH），已知其会生物转化为一系列全氟代谢物，包括全氟羧酸。用最小的实验误差来量化 FTOH 水平对于正确评估含氟调聚物材料的生物转化潜力和半衰期至关重要。我们研究了不同碳氢化合物主链的氟调聚物化合物在乙腈、甲基叔丁基醚（MTBE）和乙酸乙酯中的溶剂增强酯水解的潜力，这些化合物包括单硬脂酸酯（FTS）、柠檬酸三酯（TBC）、丙烯酸盐（FTA）和 2,4-甲苯二胺氨酯（FTU），并使用了有生命的、高压灭菌的、60Co-γ辐照的和热处理（400°C）的土壤。只有在有生命和γ辐照的土壤中，FTS 才会发生大量水解，因为微生物酶在这些土壤中是活跃的，但在高压灭菌的土壤中，酶是失活的。乙腈和甲醇（介电常数较高的溶剂）比极性较低的溶剂如 MTBE 和乙酸乙酯增强水解的程度要高一个数量级。例如，在有生命的土壤中用乙腈进行 24 小时提取 FTS 后，会产生超过 5wt.%的 FTOH，而在 MTBE 或乙酸乙酯中则不到 0.04wt.%。FTA 在 15 小时的提取期内水解率<0.7wt.%，且不依赖于溶剂。TBC、FTA 或 FTU 均未观察到统计学上显著的溶剂增强水解。
