Equilibrium sampling through membranes of freely dissolved chlorophenols in water samples with hollow fiber supported liquid membrane.
Equilibrium sampling through membranes of freely dissolved chlorophenols in water samples with hollow fiber supported liquid membrane.
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DOI：
10.1021/ac0503512
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发表时间：
2005-08
影响因子：
7.4
通讯作者：
Jing-fu Liu;J. Jönsson;P. Mayer
中科院分区：
文献类型：
--
作者：
Jing-fu Liu;J. Jönsson;P. Mayer
污染物的自由溶解浓度（C（free））通常被认为是生物可利用的，因此是造成毒性效应的原因。有机弱酸和弱碱中的游离碳由解离部分和非解离部分组成。以氯酚类化合物为模型化合物，发展了一种可忽略贫化的萃取技术--平衡膜取样法（ESTM），用于测定非解离部分的C（游离）。聚丙烯中空纤维膜（280微米内径，50-壁厚0.1微米，孔径0.1微米，长15厘米）在纤维壁的孔中浸渍十一烷作为液膜，并在内腔中填充缓冲溶液作为受体。然后，将中空纤维膜置于样品（供体）中，在密封两端后进行平衡萃取。然后通过直接进样到HPLC系统中来测定受体中的氯苯酚浓度。最后，基于其在受体中的测量浓度、其pK（a）值以及在样品和受体中的测量pH，计算氯苯酚的未解离和解离物种的C（游离）。理论计算的分配系数（D = 8-970）与实验富集因子（E（e（max））= 6-1124）吻合良好，并且观察到平衡时间随着分配系数的增加而增加（小时至天）。本文成功地测定了五种氯酚类化合物在腐殖酸模型溶液中的自由溶解浓度，其pK（a）范围为4.9-9.2，log K（ow）范围为2.35-5.24。
The freely dissolved concentration (C(free)) of pollutants is generally believed to be bioavailable and thus responsible for toxic effects. The C(free) of organic weak acids and bases consists of a dissociated and a nondissociated fraction. By using chlorophenols as model compounds, a negligible-depletion extraction technique, equilibrium sampling through membranes (ESTM), was developed for the measurement of the nondissociated part of the C(free). Polypropylene hollow fiber membranes (280-microm i.d., 50-microm wall thickness, 0.1-microm pore size, 15-cm length) were impregnated with undecane in the pores in the fiber wall as liquid membrane and filled with buffer solution in the lumen as acceptor. Then, the hollow fiber membranes were placed into the sample (donor) for an equilibrium extraction after sealing the two ends. The chlorophenol concentrations in the acceptor were then determined by direct injection into a HPLC system. Finally, the C(free) of the nondissociated and the dissociated species of a chlorophenol were calculated based on its measured concentration in the acceptor, its pK(a) value, and the measured pH in sample and acceptor. Theoretically calculated distribution coefficients (D = 8-970) agree well with the experimental enrichment factors (E(e(max)) = 6-1124), and the equilibration time was observed to increase with increasing distribution coefficients (hours to days). The freely dissolved concentration of five chlorophenols, with a wide range of pK(a) (4.9-9.2) and log K(ow) (2.35-5.24), were successfully determined in model solutions of humic acids and at low-ppb levels in river and leachate water.