An over-oxidized poly(Rutin) modified electrode for selective and sensitive determination of catechol and hydroquinone Şükriye Ulubay Karabiberoğlu a , Çağrı Ceylan Koçak b, ⁎, Zekerya Dursun a, ⁎ a Department of Chemistry, Science Faculty, Ege University, 35100, Izmir, Turkey b Bergama Vocational School, Dokuz Eylul University, 35700, Izmir, Turkey abstract article info Article history: Received 1 July 2019 Received in revised form 22 August 2019 Accepted 27 August 2019 Available online 28 August 2019 Herein, a new facile and sensitive method was developed that enables the individual and simultaneous determi- nation of catechol (CC) and hydroquinone (HQ) using an over-oxidized and electrochemically polymerised rutin film glassy carbon electrode. The proposed electrode exhibits a large peak potential difference between CC and HQ, resulting in well-separated peaks—an important factor for selective determination. CC and HQ were individ- ually and simultaneously determined via differential pulse voltammetry in a pH -7.2 phosphate buffer solution. The individually calculated detection limits for CC and HQ were 8.8 and 5.2 nM, respectively. In simultaneous de- termination, the limits of detection were calculated to be 31 and 53 nM for CC and HQ, respectively. Moreover, real sample analyses were successfully conducted using tap and waste water. © 2019 Published by Elsevier B.V. Keywords: Catechol Hydroquinone Poly(rutin) Over-oxidation Polymer film 1. Introduction Catechol (CC) and hydroquinone (HQ) are two dihydroxybenzene isomers that differ from each other in terms of the position of the hy- droxyl group in their structures [1]. They usually coexist in environmen- tal samples and are defined by the US Environmental Protection Agency (EPA) and the European Union (EU) as toxic pollutants because of their resistance towards degradation in the natural environment [2]. These environmentally toxic materials are mainly used in pesticide produc- tion, cosmetic precursors, dyes and pharmaceutical industries [3,4]. Ex- posure to either CC or HQ can cause various health problems such as headache, fatigue, liver and nervous system disorders and cancer [5,6]; thus, their selective and accurate detection is necessary. Unfortu- nately, because of their similar structures and properties, selectively and accurately determining these materials is a challenge [7]. Many analyt- ical methods, including spectrophotometry [8], chromatography [9], chemiluminescence with flow injection [10], fluorescence detection [11] and colorimetry [12] have been used for detecting CC and/or HQ. Although these techniques are adequate to determine substances, they require lengthy pretreatment steps, high operational costs and ex- pensive equipment [13]. Electrochemical techniques [14–16] are good candidates for detecting various substances because of their simple op- eration, quick response, low cost and high sensitivity [17]. In recent decades, conductive polymer (CP) films have attracted considerable attention in electrode modification as a sensing platform [18]. Their stability, biocompatibility, reproducibility and ability to de- crease surface fouling and enhance the reaction rate make them prom- ising electrode materials for improving the catalytic activity of conventional electrode surfaces [19–21]. Polymer films can modify elec- trodes via various techniques. Of all available techniques, the electro- chemical method is the most preferred technique for preparing CP films on electrode surfaces because of its better controllability, which enables the growth of thin and uniform conductive films [22]. Currently, many biological compounds, predominantly in the polymerised form, have been used for electrode modification [23,24]. Rutin is a biologically important flavonoid that is a crucial ingredient in the human diet be- cause of its antioxidant, anti-inflammatory and anticancer capacities [25,26]. To date, only few studies have reported the use of rutin as an electrode modifier [27–29]. Herein, rutin was selected as a sensing plat- form because of its active functional sites, which potentially provide en- hanced activity to analytes and enable easy polymerisation. Over-oxidation (ox) is an irreversible procedure that changes the oxidation states of polymer films and results in new sensing capabilities [30]. Through ox, active functional groups such as carbonyl, carboxyl and hydroxyl are produced on the polymer backbone. In addition, ox decreases the background current and increases the surface area be- cause of increased porosity [31,32]. Owing to these properties, ox pro- vides enhanced selectivity and sensitivity to the polymer film electrode [33]. Recently, the authors of this work published several studies on the over-oxidized polymers p-aminophenol [34], pyrrole [35] and phenol red [36] together with their applications in the Journal of Electroanalytical Chemistry 850 (2019) 113415 ⁎ Corresponding authors. E-mail addresses: ceylan.kocak@deu.edu.tr (Ç.C. Koçak), zekerya.dursun@ege.edu.tr (Z. Dursun). https://doi.org/10.1016/j.jelechem.2019.113415 1572-6657/© 2019 Published by Elsevier B.V. Contents lists available at ScienceDirect Journal of Electroanalytical Chemistry journal homepage: www.elsevier.com/locate/jelechem