Optimized multilayer oxalate biosensor

The optimization of a biosensor prepared by the immobilization of oxalate oxidase (OOX) with a cross-linking agent onto a multilayer inorganic/organic modified electrode, is presented. A very thin Prussian Blue (PB) film covered by a self-doped polyaniline (SPAN) layer acts as very sensitive amperometric sensor for the H2O2 formed by the enzymatic reaction. The electrode allows the very reliable and sensitive oxalate detection in the 0.08 to 0.45 mmol l−1 concentration range. The observed sensitivity was 131.3 μA mmol−1 cm−2 at the operation potential of 0.05 V versus Ag/AgCl in a succinate buffer solution (pH=3.8). The bilayer Prussian blue/SPAN leads to a very stable, sensitive and selective system that not only minimizes the interference caused by ascorbic and uric acids but also forms a very adherent sensing film that allows repetitive successive determinations.