Sensor 1, employed for the preliminary experiments, was a
gelatin coated rotating disc glassy carbon electrode (Tacussel CTV
101T, 3 mm diameter). Gelatin modification was performed applying
spin coating procedure, after appropriate treatment of the
electrode surface consisting in polishing, degreasing with alcohol,
and ultrasonic cleaning. Uniform and reproducible gelatin layers
were obtained by spreading a defined volume of the gelatin solution
onto the electrode surface and allowing the electrode rotate at
1000 rpm during 30 min, sufficient for the gelatin solidification at
room temperature.