A Simple Separation Method with a Microfluidic Channel Based on Alternating Current Potential Modulation Hui-Bog Noh, Pranjal Chandra, You-Jeong Kim, and Yoon-Bo Shim* Department of Chemistry and Institute of BioPhysio Sensor Technology, Pusan National University, Busan 609-735, South Korea * S Supporting Information ABSTRACT: A simple separation and detection system based on an electrochemical potential modulated microchannel (EPMM) device was developed for the first time. The application of alternating current (AC) potential to the microfluidic separation channel walls, which were composed of screen printed carbon electrodes, resulted in the oscillation and fluctuation of analytes and in the formation of a perfect flat flow front. These events resulted in an increase in the effective concentration and in the fine separation of samples. The performance of the EPMM device was examined through the analysis of endocrine disruptors (EDs) and heavy metal ions (HMIs) as model compounds. The analytical parameters that affected the separation and detection of EDs and HMIs were studied in terms of AC amplitude, AC frequency, flow rate, buffer concentration, pH, detection potential, and temperature. The separation efficiency was evaluated through measurements of the theoretical plate number (N), the retention time, and the half-peak width. Linear calibration plots for the detection of EDs and HMIs were obtained between 0.15 and 250.0 nM (detection limit 86.4 ± 2.9 pM) and between 0.01 and 10.0 nM (detection limit 9.5 ± 0.3 pM), respectively. The new device was successfully demonstrated with authentic and real samples. B y the middle of the 20th century, the separation of chemicals was mainly performed by precipitation, distillation, and extraction. However, as chemicals became more diverse and complicated due to rapid industrialization, various separation techniques, including chromatography, capillary electrophoresis, and lab-on-a-chip, expanded the applicability of separation to several fields, such as the health- care, medical, environmental science, materials science, and food science fields. Among these separation methods, chromatography has been extensively developed over the past 50 years, 1-3 which has consequently led to the development of gas, 4 liquid, 5 and supercritical-fluid 6 chromatographic techni- ques. Although chromatography has been frequently used because of its excellent separation capability for multiple components present in trace amounts, the long measuring time and easy changes in the experimental parameters cause deterioration of analytes. As a consequence, chromatography cannot be used for the separation of samples that exhibit instability or contain large analytes. In addition, the other conventional methods of electrophoresis, 7-9 capillary electro- phoresis, 10-12 and field-flow fractionation (FFF) 13-15 were also developed chronologically for the efficient separation and detection of diverse samples including proteins, DNA, RNA, inorganic ions, and vitamins. Recently, the micro-total analysis system (μ-TAS) technique has been successfully implemented in microfluidic devices for the separation of chemicals based on conventional electro- phoretic 16-19 and pressure-flow microchannel devices. 20-25 In addition, other external fields or driving forces, such as the capillary effect, electric fields, magnetic fields, and rotation, have been reported for the separation of samples in microfluidic devices. 26 Along with these separation methods, the develop- ment of techniques that introduce electrochemical method- ologies using a separation channel with porous Vycor glass with an electrode installed inside the channel tube has also been attempted. 27,28 The development of this technique was almost discontinued due to technical problems that arose with the porous separation channel. Thus, we attempted to develop a new separation technique using a microfluidic channel constructed with carbon electrodes that apply an alternating current (AC) potential to the channel walls. We refer to this technique as the electrochemical potential modulated micro- channel (EPMM) system. This technique is different from those previously reported, where an AC potential was applied in the separation solution or at only few points along a single side of the channel wall and AC electroosmotic trapping. 29 No method similar to EPMM has been reported, where the AC potential is applied to the walls of two planar carbon electrodes that compose a channel. This EPMM device is expected to allow the rapid and simple separation of various chemicals and to improve the weaknesses of conventional separation methods. The application of an AC potential to the separation channel Received: May 18, 2012 Accepted: October 17, 2012 Published: October 17, 2012 Article pubs.acs.org/ac © 2012 American Chemical Society 9738 dx.doi.org/10.1021/ac301351y | Anal. Chem. 2012, 84, 9738-9744