Journal of Chromatography A, 1324 (2014) 21–28 Contents lists available at ScienceDirect Journal of Chromatography A jou rn al hom epage: www.elsevier.com/locate/chroma Voltage-step pulsed electromembrane as a novel view of electrical field-induced liquid-phase microextraction Maryam Rezazadeh a , Yadollah Yamini a,∗ , Shahram Seidi b , Leila Arjomandi-Behzad a a Department of Chemistry, Tarbiat Modares University, P.O. Box 14115-175, Tehran, Iran b Department of Analytical Chemistry, Faculty of Chemistry, K.N. Toosi University of Technology, Tehran, Iran a r t i c l e i n f o Article history: Received 25 September 2013 Received in revised form 11 November 2013 Accepted 14 November 2013 Available online 22 November 2013 Keywords: Pulsed electromembrane Microextraction Voltage steps Stability Low voltage a b s t r a c t In the present work, the effect of application of voltage steps on extraction efficiency of pulsed elec- tromembrane extraction (PEME) was investigated for the first time. The effects of voltage variations including initial and final voltages, number of steps between the initial and final voltages as well as their time durations were studied on the extraction efficiencies of three different classes of analytes. These classes include amitriptyline (AMI) and nortriptyline (NOR) as more hydrophobic analytes, diclofenac (DIC) and mefenamic acid (MEF) as acidic drugs and salbutamol (SB) and terbutaline (TB) as hydrophilic compounds. It was anticipated that the application of high voltages is not necessary at the beginning of the extraction, since large amounts of target analytes exist around the supported liquid membrane (SLM)/sample solution interface. So, they could be easily transferred into the acceptor phase utilizing lower voltages. Results showed that the benefits of voltage-step PEME (VS-PEME) are more obvious in systems with low electrical resistance (regarding the SLM composition). Efficiencies of VS-PEME for extraction of AMI and NOR (96% and 89% for AMI and NOR, respectively) were comparable with those achieved from applying a constant voltage (95% for AMI and 83% for NOR). However, recoveries from the VS-PEME of DIC and MEF (53% and 44% for DIC and MEF, respectively) were significantly higher than those from the application of a constant voltage (33% for DIC and 31% for MEF). Also, recoveries obtained from the VS-PEME for SB and TB were approximately 3 orders of magnitude greater than those from a constant voltage. Moreover, it was demonstrated that in all cases analytes could effectively be extracted at the beginning of extraction by applying low voltages. © 2013 Elsevier B.V. All rights reserved. 1. Introduction Electromembrane extraction (EME) is a micro-scaled electri- cal field-induced liquid-phase extraction technique which was introduced in 2006 [1]. EME is capable of effectively extracting ion- izable compounds utilizing an electrical field to make them migrate from an aqueous sample solution into an aqueous acceptor phase through the supported liquid membrane (SLM). Due to the many benefits such as high efficiency, selectivity, sample cleanup and fast kinetics which have been found for this microextraction method, it is associated with rapidly progressing. Up to now, several stud- ies have been performed to figure out the impressive variables and the exact mechanism of this technique [1–6]. Furthermore, a lot of developments have been reported to improve the advantages and overcome the drawbacks of this new microextraction method; such as a new setup for exhaustive EME [7,8], simultaneous extraction of acidic and basic drugs at neutral sample pH [9,10], EME coupling ∗ Corresponding author. Tel.: +98 21 82883417; fax: +98 21 88006544. E-mail addresses: yyamini@modares.ac.ir, yyamini2002@yahoo.com (Y. Yamini). with dispersive liquid–liquid microextraction (DLLME) [11,12] and solid-phase microextraction (SPME) [13] to make it compatible with GC instrument and some EME designs for development of lab-on-chip systems [14–16]. The main trouble with EME is system instability as a result of an increase in the current level when high voltages are applied; espe- cially in analysis of real samples containing large amounts of ionic components. Therefore, Kubá ˇ n et al. set an electrical design to con- trol the level of electrical current during the extraction process [17]. To this end, a high voltage power supply was employed to provide stabilized constant DC current down to 1 A. On the other hand, Yamini et al. presented a simple and inexpensive setup based on the application of pulsed voltages to overcome the problems EME faces in analysis of real samples [18]. They used an electronic device, which created pulsed voltages, in combination with a common con- stant DC power supply to minimize the thickness of double layer formed by the ambulations of ions on both sides of the SLM. In each pulse, voltage is applied for a relatively short time which is long enough for the analytes transportation into the accep- tor phase. During the outage period, the ions accumulated at the interfaces were dispersed again throughout the stirring sample 0021-9673/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.chroma.2013.11.034