705 Acta Chim. Slov. 2016, 63, 705–712 Nikoofard and Solbi: Electro-catalytic Oxidation of Catechol ... Scientific paper Electro-catalytic Oxidation of Catechol at Poly(1-amino-9,10-anthraquinone)-SDS Composite Film Hossein Nikoofard* and Malihe Solbi Faculty of Chemistry, Shahrood University of Technology, Shahrood 36199-95161, Iran * Corresponding author: E-mail: hnikoofard@shahroodut.ac.ir Tel.: +98 23 3239 5441; Fax: +98 23 3239 5441 Received: 18-01-2016 Abstract An electro-chemically active composite film containing the environmentally friendly surfactant sodium dodecyl sulfa- te (SDS) and poly(1-amino-9,10-anthraquinone) (PAAQ) is used as an electron transfer mediator in the electro-chemi- cal oxidation of catechol. Compared with the bare platinum (Pt) electrode, the Pt/PAAQ-SDS modified electrode remar- kably lowers the anodic peak potential of catechol, and increases the peak currents. The results obtained indicate that the activation energy for the electro-chemical oxidation of catechol at the polymer film is low (7.05 kJ mol –1 ). The influen- ce of the operational conditions on the response current of the catechol sensor is also investigated. Studying the surface morphology of the modified electrode reveals a more porous structure for it due to the incorporation of the anionic sur- factant on the PAAQ film. The modified electrode displays a linear response in the concentration range of 0.01–8.0 m- M for catechol. A lower detection limit was obtained to be 2.60 μM. The ability of the modified electrode is also exami- ned for the electro-chemical detection of hydroquinone (HQ) with simplicity. Keywords: Electro-catalytic oxidation; Coated polymeric film; Catechol; Poly(1-amino-9,10-anthraquinone) (PAAQ); Sodium dodecyl sulfate (SDS). 1. Introduction Catechol (1,2-dihydroxybenzene) is one of the most important phenolic compounds occurring naturally in the environment. Catechol-based compounds are formed du- ring the biological degradation processes, and are used in a wide range of industrial applications. 1,2 In addition, they are of biological importance; for instance, they have anti-oxidation and anti-viral activities and flower stimu- lating effects and affect the activities of some enzymes. 3,4 On the other hand, they are highly toxic to the humans, animals, plants, and aquatic life when present above cer- tain concentration limits. 5–7 Several analytical techniques such as spectrophotometry 8 and high pressure liquid chromatography (HPLC) 9 have been used for the deter- mination of catechol and its derivatives. However, these methods are usually costly, complicated, and time-consu- ming procedures for routine analyses. The electro-chemi- cal techniques are promising approaches due to their sen- sitivity, rapidity, and simplicity. The direct electro-chemical determination of catec- hol at common electrodes shows important disadvanta- ges such as high over-potential, poor selectivity, irrever- sibility, and electrode fouling. 10,11 These difficulties can be minimized using an electro-chemically modified electrode, which can minimize or overcome most of the above-mentioned problems. Modified electrodes contain redox mediators, which have the ability to improve the rate of electron transfer from the substrate to the electro- de. 12,13 It has been found that many redox materials have been used as the electron transfer mediators for the elec- tro-chemical oxidation of catechol. These modified elec- trodes contain various quinone derivatives, nano-partic- les, and some conducting polymers. 14–19 In this regard, electro-polymerization is a simple and powerful method that can be implemented in targeting a selective modifi- cation of different types of substrates with the desired materials. Poly(1-amino-9,10-anthraquinone) (PAAQ), a conducting polymer, has received a considerable atten- tion due to its excellent properties such as environmental stability, good electro-activity, high electrical conducti- vity, powerful specific electro-capacity, fast reversible redox ability, and its use as an electrode for biosen- sors. 20–24 DOI: 10.17344/acsi.2016.2260