Prussian Blue/Carbon Nanotube Sensor Spread with Gelatin/Zein Glaze: A User-Friendly Modification for Stable Interference-Free H 2 O 2 Amperometry.

We report the production and characterization of effective amperometric sensors for cathodic hydrogen peroxide (H 2 O 2 ) detection. The proposed electrodes involve a combination of a H 2 O 2 -signaling Prussian Blue (PB)/carbon nanotube (CNT) layer with a glaze of the biopolymers gelatin (top) and zein (beneath) for protection against PB leakage. The sandwich-type sensor was constructed through simple "drop and dry" steps with (1) suspensions of the CNTs in a soluble PB solution, (2) zein in ethanol, and (3) gelatin in water, applied sequentially to the carbon working electrode disk of a screen-printed carbon electrode (SPCE) platform. The PB in the signaling layer acted as the electrocatalyst for H 2 O 2 reduction at -150 mV vs Ag/AgCl/3 M KCl, enabling cathodic H 2 O 2 amperometry with good target proportionality. Calibration trials confirmed the linearity of the response up to 700 μM ( R 2 > 0.998), with a sensitivity of 0.425 μA μM -1 cm -2 and a practical detection limit of 1 μM. Quantification of H 2 O 2 in model and real samples with gelatin-zein-PB/CNT-SPCEs had a recovery of close to 100% of the true value. Since they are easily and cheaply made and yield accurate target assessments, gelatin-zein-PB/CNT-SPCEs are an ideal tool for electrochemical H 2 O 2 analyses in human body fluids, health care products, and samples from industries that use H 2 O 2 as a bleach and germicide. Workers with little experience in sensor fabrication and limited funding will particularly benefit from utilization of the proposed H 2 O 2 probes, which as well as being used in H 2 O 2 testing also have a potential application as the transducer unit of oxidase-based biosensors with amperometric H 2 O 2 readout.