Electrochimica Acta 123 (2014) 485–493 Contents lists available at ScienceDirect Electrochimica Acta j ourna l ho me page: www.elsevier.com/locate/electacta A flow injection analysis coupled dual electrochemical detector for selective and simultaneous detection of guanine and adenine Rajendiran Thangaraj a , Subramanian Nellaiappan a , Raja Sudhakaran b , Annamalai Senthil Kumar a,∗ a Environmental and Analytical Chemistry Division, School of Advanced Sciences, Vellore Institute of Technology University, Vellore-632 014, India b Aquaculture Biotechnology Laboratory, School of Bioscience and Technology, Vellore Institute of Technology University, Vellore-632 014, India a r t i c l e i n f o Article history: Received 1 November 2013 Received in revised form 9 January 2014 Accepted 10 January 2014 Available online 23 January 2014 Key words: Flow injection analysis Dual electrochemical detector Bipotentiostat Guanine Adenine. a b s t r a c t Adenine (A) and guanine (G), important bases of nucleic acids, are often analyzed by separation cou- pled spectroscopic detection methods. Herein, we are demonstrated a new flow-injection analysis (FIA) coupled dual electrochemical detector (DECD), where a chitosan-carbon nanofiber (Chit-CNF) modified glassy carbon electrode prepared by a simple technique and pH 7 phosphate buffer solution as a carrier system, for separation-less quantification of G and A. This method is highly selective and no interference by the presence of the other DNA bases (Thymine and Cytosine). The FIA-DECD was operated at two different operating potentials, E1 = 0.80 V and E2 = 0.95 V vs Ag/AgCl, where G and {G + A} get oxidized, respectively. Amount of A was calculated from the difference between the FIA current signals, mea- sured at E2 0.95V and E1 0.80V . The GCE/Chit-CNF was characterized by cyclic voltammetry with potassium ferricyanide system and Raman spectroscopy. The modified electrode showed unique electron-transfer feature with metal like conductivity. Under an optimal condition, FIA-DECD showed linear calibration plots for G and A in a concentration range, 200 nM—50 M with current sensitivity values 13.83 ± 0.48 and 4.84 ± 0.11 nA M -1 respectively. Calculated detection limit (signal-to-noise ratio = 3) values were 46.8 nM and 73.8 nM for G and A respectively. Applicability of the present technique was further demon- strated by detecting G and A in beef kidney sample and DNA hybridization process. © 2014 Elsevier Ltd. All rights reserved. 1. Introduction Adenine (A) and guanine (G) are the building blocks of both deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) that plays a crucial role in protein biosynthesis and the storage of genetic information [1]. Selective and sensitive detection of the purine bases provides valuable insights in fundamental fields such as understanding of DNA sequence, oxidative damage and hybridiza- tion and protein metabolism in cells, protein-DNA interactions, etc [2–4]. Commonly used quantification technique for G and A are separation coupled spectroscopic methods. For instance, ion-pair reversed phase high performance liquid chromatography and capillary electrophoresis coupled UV [1,5,6], micellar electroki- netic chromatography with indirect laser-induced fluorescence detection (ILIFD) [7] and high performance liquid chromatography coupled mass spectrophotometer (HPLC-MS) [8] techniques were reported for the detection of G and A. Each method has its own ∗ Corresponding author. Tel.: +91 416 2202754; fax: +91 416 2243092. E-mail address: askumarchem@yahoo.com (A.S. Kumar). strengths and weakness in terms of analytical performance. UV based detectors are versatile; however owing to low extension coefficient, sensitivity of the signals are very low. Similarly, the ILIFD and mass spectroscopy based detection technique allow to detect low concentration of purine bases; beside with respect to the instrumentation cost, off-line sampling preparation, run-time and skilled person requirement, the above techniques are not suitable for routine analytical measurements. Hence, it is highly challenging research to develop a new technique which full fills all majority of the above mentioned criteria. Herein, we introduce a dual electrochemical detector (DECD) based flow injection analysis technique (FIA-DECD) for rapid and simultaneous detection of G and A without any derivatization and separation procedure. Electro-analytical techniques offer simple, less-expensive, highly sensitive and selective analytical approach extendable to disposable type screen printed electrode and miniaturization. In the past, there were several electrochemical methods (cyclic and pulse voltammetric techniques), in which various chemically modified electrodes (CMEs) as working systems were reported for simultaneous detection of G and A with the test sample volume about 10 mL. Following are the representative CMEs: 0013-4686/$ – see front matter © 2014 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.electacta.2014.01.066