Development of electrochemical sulfite biosensor based on SOX/PBNPs/PPY modified Au electrode

A sulfite oxidase (SOX) (EC 1.8.3.1) purified from Syzygium cumini leaves was immobilized onto Prussian blue nanoparticles/polypyrrole (PBNPs/PPY) nanocomposite film electrodeposited onto the surface of gold (Au) electrode. An electrochemical sulfite biosensor was fabricated using SOX/PBNPs/PPY/Au electrode as working electrode, Ag/AgCl as standard electrode 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) at different stages of its construction. The biosensor showed optimum response within 2 s, when operated at 20 mV s−1 in 0.1 M Tris–HCl buffer, pH 8.0 and at 30 °C. Linear range and minimum detection limit were 0.5–1000 μM and 0.1 μM (S/N = 3) respectively. The sensor was evaluated with 95.0% recovery of added sulfite in red wine samples and 1.9% and 3.3% within and between batch coefficients of variation respectively. There was a good correlation (r = 0.96) between red wine samples sulfite value by standard DTNB method and the present method. The sensor was employed for determination of sulfite level in red, white and rose wine samples. The enzyme electrode was used 300 times over a period of 4 months, when stored at 4 °C.

► Development of sulfite biosensor based on SOX/PBNPs/PPY/Au electrode.
► Biosensor showed optimum response within 2 s, at 20 mV s−1, pH 8.0 and 30 °C.
► Linear range and detection limit were 0.5–1000 μM and 0.1 μM.
► Biosensor measured sulfite in red, rose and white wine samples.
► Electrode used 300 times over a period of 120 days when stored at 4 °C.