School of Pharmacy, University of Oslo, Oslo, Norway.
Anal Chim Acta. 2012 Sep 12;742:10-6. doi: 10.1016/j.aca.2011.12.039. Epub 2011 Dec 27.
In this paper, extraction kinetics was investigated experimentally and theoretically in hollow fiber liquid-phase microextraction (HF-LPME) and electromembrane extraction (EME) with the basic drugs droperidol, haloperidol, nortriptyline, clomipramine, and clemastine as model analytes. In HF-LPME, the analytes were extracted by passive diffusion from an alkaline sample, through a (organic) supported liquid membrane (SLM) and into an acidic acceptor solution. In EME, the analytes were extracted by electrokinetic migration from an acidic sample, through the SLM, and into an acidic acceptor solution by application of an electrical potential across the SLM. In both HF-LPME and EME, the sample (donor solution) was found to be rapidly depleted for analyte. In HF-LPME, the mass transfer across the SLM was slow, and this was found to be the rate limiting step of HF-LPME. This finding is in contrast to earlier discussions in the literature suggesting that mass transfer across the boundary layer at the donor-SLM interface is the rate limiting step of HF-LPME. In EME, mass transfer across the SLM was much more rapid due to electrokinetic migration. Nevertheless, mass transfer across the SLM was rate limiting even in EME. Theoretical models were developed to describe the kinetics in HF-LPME, in agreement with the experimental findings. In HF-LPME, the extraction efficiency was found to be maintained even if pH in the donor solution was lowered from 10 to 7-8, which was below the pK(a)-value for several of the analytes. Similarly, in EME, the extraction efficiency was found to be maintained even if pH in the donor solution increased from 4 to 11, which was above the pK(a)-value for several of the analytes. The two latter experiments suggested that both techniques may be used to effectively extract analytes from samples in a broader pH range as compared to the pH range recommended in the literature.
本文以droperidol、haloperidol、nortriptyline、clomipramine 和 clemastine 等碱性药物为模型分析物，通过实验和理论研究了中空纤维液相微萃取（HF-LPME）和电膜萃取（EME）中的萃取动力学。在 HF-LPME 中，分析物通过从碱性样品中的被动扩散，穿过（有机）支撑液膜（SLM）并进入酸性接受溶液来提取。在 EME 中，分析物通过电迁移从酸性样品中提取，穿过 SLM，并通过在 SLM 上施加电势而进入酸性接受溶液。在 HF-LPME 和 EME 中，都发现样品（供体溶液）迅速耗尽分析物。在 HF-LPME 中，SLM 内的质量转移缓慢，这被发现是 HF-LPME 的限速步骤。这一发现与文献中早些时候的讨论形成对比，文献中提出，在供体-SLM 界面处的边界层内的质量转移是 HF-LPME 的限速步骤。在 EME 中，由于电迁移，SLM 内的质量转移要快得多。尽管如此，即使在 EME 中，SLM 内的质量转移也是限速步骤。开发了理论模型来描述 HF-LPME 中的动力学，与实验结果一致。在 HF-LPME 中，即使将供体溶液的 pH 值从 10 降低至 7-8，低于几种分析物的 pK(a)-值，萃取效率也被发现得以维持。同样，在 EME 中，即使将供体溶液的 pH 值从 4 增加至 11，高于几种分析物的 pK(a)-值，萃取效率也被发现得以维持。这两个实验表明，与文献中推荐的 pH 范围相比，这两种技术都可用于从更宽的 pH 范围内的样品中有效提取分析物。
