Journal of Scientific & Industrial Research Vol. 78, March 2019, pp. 177-181 Electrochemical Determination of Guanine and Uric Acid using NdFeO 3 Nps Modified Graphite Paste Electrode Y Kumar 1 , P P Singh 2 , P Pramanik 3 and D Das 4 * 1,2,3,4 Department of Chemistry, GLA University, Mathura, 281406 India Received 05 June 2018; revised 17 December 2018; accepted 03 February 2019 Electro-catalytic activities of neodymium ortho-ferrite (NdFeO 3 ) nano-particles for determination of bio molecules like guanine (GU) and uric acid (UA) in biological fluids have been investigated in this report. The perovskite type NdFeO 3 nps were used as electrode modifier for determination of these bio-molecules individually as well as in mixture. The electrochemical catalytic activities of modified electrodes were studied by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. The efficient identification of bio-molecules may be due to unique band gap. The detection limits of GU and UA were 250 and 350 nM respectively, maintaining the linear range from 0.5 to 100 µM for GU and 1.0 to 120 µM for UA. Phosphate buffer solution of pH 5.0 was used as supporting electrolyte in all electrochemical measurements with scan rates 100 and 50 mVs -1 for CV and DPV respectively. Keywords: Electrochemical-Catalyst, NdFeO 3 , Nanoparticles, Electrochemical Determination, Guanine, Uric Acid Introduction For clinical diagnosis and pharmaceutical industry, it is very essential to develop a useful, cheap and sensitive electrode, capable to determine bio/drug molecules in bio fluids, separately as well as in their mixtures. The conventional techniques for determination of bio molecules are expensive. Hence, the researchers have been attracted towards electrochemical techniques due to advantages like fast response, better selectivity, high sensitivity and low cost. Several materials like Co doped CeO 2 nanoparticles 1 , MWCNT-Fe 3 O 4 @PDA-Ag nanocomposite 2 , nitrogen doped graphene nps 3 , reduced graphene oxide 4 , nickel telluride and cobalt telluride nps 5 , PbTe/GP electrode 6 , glassy carbon electrode fabricated with zinc oxide 7 ,lanthanide- orthoferrites (XFeO 3 /GP) 8 , and urease immobilized biosensor for determination of urea 9 have been used as electrode materials. Here we report neodymium ortho-ferrite modified graphite paste (NdFeO 3 /GP) electrode, for electrochemical determination of GU & UA both separately as well as in mixture. As far as we are aware, it is the first report on the determination of GU & UA and its mixture using neodymium ortho-ferrite as electrode modifier. Experimental Chemicals and reagents Uric acid (C 5 H 4 N 4 O 3 ) and guanine (C 5 H 5 N 5 O) were procured from Sigma Aldrich, USA. Both the chemicals were of AR grade and used without further purification. All the solutions were prepared in double distilled water. Preparation of electrode A capillary glass tube (2 mm inner diameter) was used to make NdFeO 3 modified graphite paste (NdFeO 3 /GP) electrode. A uniform paste of graphite powder and synthesized nps of NdFeO 3 (ratio 4:1, w/w) was filled in glass tube and packed tightly by pressing with metal rod. From the back side of the capillary tube, platinum wire was inserted for electrical contact. Similar fabrication process was followed for the preparation of bare GP electrodes. Al 2 O 3 slurry (0.5 mM) was used to clean the electrode’s surface. Finally the electrodes were wiped with ethanol and dried under N 2 atmosphere prior to experimentation. Apparatus and measurements Three electrode system potentiostate/galvanostate, Autolab101 (Netherlands) was used to perform electrochemical measurements. In this system, the Ag/AgCl electrode as reference electrode, Pt electrode as counter electrode and newly prepared electrode as working electrode were used. Phosphate buffer solution _____ *Author for Correspondence E-mail: deepak.das@gla.ac.in