Development of an amperometric sulfite biosensor based on SOx/PBNPs/PPY modified ITO electrode

A sulfite oxidase (SOx) (EC 1.8.3.1) purified from Syzygium cumini leaves was immobilized onto prussian blue nanoparticles/polypyrrole composite (PBNPs/PPY) electrodeposited onto the surface of indium tin oxide (ITO) electrode. An amperometric sulfite biosensor was fabricated using SOx/PBNPs/PPY/ITO electrode as working electrode. Ag/AgCl as standard and Pt wire as auxiliary electrode connected through a potentiostat. The working electrode was characterized by Fourier transform infrared (FTIR) spectroscopy, cyclic voltammetry (CV), scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS) before and after immobilization of SOx. The biosensor showed optimum response within 2s, when operated at 20 mV s(-1) in 0.1 M Tris-HCl buffer, pH 8.5 and at 35 degrees C. Linear range and minimum detection limit were 0.5-1000 mu M and 0.12 mu M (S/N = 3) respectively. There was good correlation (r = 0.99) between red wine samples sulfite value by standard DTNB method and the present method. The sensor was evaluated with 97% recovery of added sulfite in red wine samples and 2.2% and 4.3% within and between batch coefficients of variation respectively. The sensor was employed for determination of sulfite level in red and white wine samples. The enzyme electrode was used 200 times over a period of 3 months when stored at 4 degrees C. (C) 2012 Elsevier B.V. All rights reserved.