Helmholtz Centre for Environmental Research UFZ, Leipzig, Germany.
Anal Bioanal Chem. 2013 Mar;405(8):2567-74. doi: 10.1007/s00216-012-6689-9. Epub 2013 Jan 12.
Experimental determination of oil-water partition coefficients often poses difficulties associated with emulsion formation. The aim of this work was to find an appropriate technique for determination of oil-water partition coefficients of polar, nonvolatile compounds. Two different methods were tested. The first method used a "silicone membrane equilibrator." For the second method, solid-phase microextraction (SPME) fibers with a polyacrylate (PA) coating were used as a passive sampler. With both methods, oil-water partition coefficients for 14 compounds with polar functional groups were determined at 37 °C with good repeatability (standard deviation 0.11 log units or lower). The partition coefficients determined with the silicone membrane equilibrator method ranged from 0.50 to 3.49 log units. The oil-water partition coefficients obtained with the PA-SPME passive sampling approach were significantly higher than those obtained with the silicone membrane equilibrator method for nine of 14 compounds. The differences were up to 0.39 log units (i.e., a factor of 2.5). Additional experiments suggested that this difference occurred because the sorption properties of the PA fibers used were influenced by the surrounding phase, e.g., through swelling of the polymer phase. Therefore, the SPME passive sampling method using PA fibers seems to be less reliable, whereas the silicone membrane equilibrator method was found to be a convenient technique for the determination of oil-water partitioning.
实验测定油水分配系数通常会遇到与乳状液形成相关的困难。本工作旨在寻找一种合适的技术，用于测定具有极性、非挥发性化合物的油水分配系数。测试了两种不同的方法。第一种方法使用“硅膜平衡器”。对于第二种方法，使用聚丙稀酸酯（PA）涂层的固相微萃取（SPME）纤维作为被动采样器。对于这两种方法，在 37°C 下，对 14 种具有极性官能团的化合物进行了油水分配系数的测定，重复性良好（标准偏差为 0.11 个对数单位或更低）。用硅膜平衡器法测定的分配系数范围为 0.50 至 3.49 个对数单位。用 PA-SPME 被动采样法得到的油水分配系数对于 14 种化合物中的 9 种明显高于硅膜平衡器法。差异高达 0.39 个对数单位（即 2.5 倍）。进一步的实验表明，这种差异是由于所用的 PA 纤维的吸附性能受到周围相的影响，例如聚合物相的溶胀。因此，使用 PA 纤维的 SPME 被动采样法似乎不太可靠，而硅膜平衡器法被发现是一种用于测定油水分配的方便技术。
