Electrophoresis 2014, 00, 1–8 1 Bruno Gabriel Lucca 1 Susan Marie Lunte 2 Wendell Karlos Tomazelli Coltro 3 Valdir Souza Ferreira 1 1 Instituto de Qu´ ımica, Universidade Federal de Mato Grosso do Sul, Campo Grande, MS, Brazil 2 Ralph N. Adams Institute for Bioanalytical Chemistry, University of Kansas, Lawrence, KS, USA 3 Instituto de Qu´ ımica, Universidade Federal de Goi ´ as, Goi ˆ ania, GO, Brazil Received April 8, 2014 Revised August 27, 2014 Accepted August 28, 2014 Research Article Separation of natural antioxidants using PDMS electrophoresis microchips coupled with amperometric detection and reverse polarity This report describes the use of PDMS ME coupled with amperometric detection for rapid separation of ascorbic, gallic , ferulic, p-coumaric acids using reverse polarity. ME devices were fabricated in PDMS by soft lithography and detection was accomplished using an integrated carbon fiber working electrode aligned in the end-channel configuration. Sepa- ration and detection parameters were investigated and the best conditions were obtained using a run buffer consisting of 5 mM phosphate buffer (pH 6.9) and a detection voltage of 1.0 V versus Ag/AgCl reference electrode. All compounds were separated within 70 s using gated injection mode with baseline resolution and separation efficiencies between 1200 and 9000 plates. Calibration curves exhibited good linearity and the LODs achieved ranged from 1.7 to 9.7 M. The precision for migration time and peak height provided maximum values of 4% for the intrachip studies. Lastly, the analytical method was successfully ap- plied for the analysis of ascorbic and gallic acids in commercial beverage samples. The results achieved using ME coupled with amperometric detection were in good agreement with the values provided by the supplier. Based on the data reported here, the proposed method shows suitability to be applied for the routine analysis of beverage samples. Keywords: Electrochemical detection / Foodomics / Microfluidic devices / Phenolic compounds / Reverse polarity DOI 10.1002/elps.201400359  Additional supporting information may be found in the online version of this article at the publisher’s web-site 1 Introduction Free radical reactions can cause the deterioration of food quality, nutritional losses, and changes in lipids composition. Several kinds of antioxidants have been used to improve the stability of food products, however, the growing use of syn- thetic antioxidants in foods and beverages is becoming a con- cern. Therefore, studies regarding the content and stability of natural antioxidants in foods and beverages are becoming Correspondence: Professor Valdir Souza Ferreira, Instituto de Qu´ ımica, Universidade Federal de Mato Grosso do Sul, Cidade Universit ´ aria, 79074-460, P.O. Box 549, Campo Grande, MS, Brazil E-mail: valdir.souza@ufms.br Abbreviations: AA, ascorbic acid; ED, electrochemical de- tection; GA, gallic acid; TTAB, tetradecyltrimethylammonium bromide increasingly prevalent. These natural antioxidants include ascorbic acid (AA) and phenolic compounds [1–5]. Many different types of phenolic compounds are found in plants with phenolic acids and flavonoids being the pre- dominant species [6]. Some of these phenolic compounds have been shown to be protective against inflammation, ox- idation, cancer, viruses, and bacteria. The health benefits of naturally occurring phenolic compounds have been reported extensively in the literature [7–10]. Another naturally occur- ring antioxidant, AA, is a vitamin that is present in a large number of fruits and vegetables. Similar to the phenolic com- pounds, AA exhibits antioxidant properties and is frequently added to food products in order to stabilize color and aroma and prolong their shelf life [11]. There are many reports of analytical methods for the de- termination of phenolic compounds in food and beverage samples. Most of these employ LC for separation of the rele- vant species followed by detection by MS, but other detection techniques also are used [12–18]. A disadvantage of LC-MS C  2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.electrophoresis-journal.com