Volatile solvents are excellent extraction media for liquid-liquid extractions. However, their use in supported liquid membranes (SLMs) is limited by their evaporation from SLM and thus poor SLM stability and they have never been considered truly useful for electromembrane extraction (EME). In this contribution, volatile solvents were systematically investigated as liquid membranes for EME and their extraction characteristics were comprehensively examined for the first time. A short plug of a water immiscible volatile solvent (a free liquid membrane (FLM)) was sandwiched between two aqueous plugs (donor and acceptor solutions) in a narrow-bore polymeric tubing. Evaporation of the volatile FLM was thus completely avoided and excellent stability of the phase interface was ensured. Suitability of volatile FLMs for EMEs was justified by μ-EMEs of nortriptyline, haloperidol, loperamide and papaverine as model non-polar basic drugs. Extraction performance of μ-EME through ethyl acetate was comparable or better to that through standard non-volatile EME solvents and a high extraction selectivity was achieved for nortriptyline and haloperidol extracted through chloroform. μ-EMEs through the volatile FLMs were characterized by high extraction recoveries (62% – 99% for standards and 40 – 89% for body fluids), low electric currents (10 – 1380 nA), no susceptibility to matrix ions and suitability for pretreatment of raw body fluids (human urine and serum). Resulting extracts were analysed by capillary electrophoresis with ultraviolet detection (CE/UV). Repeatability of the μ-EME-CE/UV method was excellent with intra-day and inter-day RSD values 0.8 – 3.2% and 1.8 – 4.6%, respectively. Further experiments demonstrated additional advantages of volatile FLMs by nearly exhaustive μ-EMEs of atenolol as the polar basic drug with no need for FLM modification by ionic carriers. The presented comprehensive examination of volatile solvents has broadened the range of liquid membranes suitable for EME and it is believed that this proof-of-concept study will stimulate further interest in a deeper investigation of volatile phase interfaces in EME.

挥发性溶剂是用于液-液萃取的出色萃取介质。但是，它们在支撑液膜（SLM）中的使用受到它们从SLM蒸发的限制，因此SLM稳定性差，并且从未被认为对电膜萃取（EME）真正有用。在这一贡献中，系统地研究了挥发性溶剂作为EME的液膜，并首次全面研究了其萃取特性。与水不混溶的挥发性溶剂（自由液膜（FLM））的短塞夹在窄孔聚合物管中的两个水性塞（供体和受体溶液）之间。因此，完全避免了挥发性FLM的蒸发，并确保了相界面的出色稳定性。用去甲替林，氟哌啶醇，洛哌丁胺和罂粟碱的μ-EME作为模型非极性碱性药物证明了挥发性FLM对EME的适用性。通过乙酸乙酯对μ-EME的萃取性能与标准非挥发性EME溶剂相当或更好，对去甲替林和氟哌啶醇的氯仿萃取具有很高的萃取选择性。通过挥发性FLM产生的μ-EME具有以下特点：高提取回收率（标准品的回收率为62％– 99％，体液为40– 89％），低电流（10 – 1380 nA），对基质离子无敏感性以及适合预处理原液（人尿和血清）。通过毛细管电泳和紫外检测（CE / UV）分析所得提取物。μ-EME-CE/ UV方法的重复性极好，日内和日间RSD值分别为0.8 – 3.2％和1.8 – 4.6％。进一步的实验证明，几乎无穷尽的阿替洛尔μ-EME作为极性碱性药物，具有挥发性FLM的其他优势，而无需通过离子载体修饰FLM。目前对挥发性溶剂的全面检查扩大了适用于EME的液膜的范围，并且相信这一概念验证研究将激发人们对EME中挥发性相界面进行更深入研究的兴趣。