Mediated xanthine oxidase potentiometric biosensors for hypoxanthine based on ferrocene carboxylic acid modified electrode

A potentiometric enzyme electrode for detection of hypoxanthine (Hx) in fish meat is described. The sensor was developed by entrapment of xanthine oxidase (XOD) and ferrocene carboxylic acid (Fc) into polypyrrole (PPy) film during galvanostatic polymerisation film formation. The responses for Hx were obtained in 0–05 M phosphate buffer (pH 7.1) at 0.0 mV vs Ag/AgCl (3 M KCl). The optimum condition for the formation of PPy–XOD–Fc film include 0.4 M PPy, 6.2 U/mL XOD, 40 mM Fc, polymerisation time of 200 s and applied current density of 0–5 mA cm−2. The sensor provides a linear response to Hx in concentration range of 5–20 μM, (r = 0.998) and was successfully used for determination of Hx in fish.