Nano-palladium-decorated bismuth sulfide microspheres on a disposable electrode integrated with smartphone-based electrochemical detection of nitrite in food samples.

Nitrite (NO) is widely used as an additive to extend the shelf life of food products. Excessive nitrite intake not only causes blood-related diseases but also has the potential risk of causing cancers. A disposable screen-printed electrode was modified with nano‑palladium decorated bismuth sulfide microspheres (nanoPd@BiSMS/SPE), and integrated with a smartphone-interfaced potentiostat to develop a portable, electrochemical nitrite sensor. NanoPd@BiSMS was prepared by the hydrothermal reduction of a BiSMS and Pd dispersion and drop cast on the SPE. The nanoPd@BiSMS/SPE was coupled with a smartphone-controlled portable potentiostat and applied to determine nitrite in food samples. The linear range of the sensor was 0.01-500 μM and the limit of detection was 0.0033 μM. The proposed system showed good repeatability, reproducibility, catalytic stability, and immunity to interferences. The proposed electrode material and a smartphone-based small potentiostat created a simple, portable, fast electrochemical sensing system that accurately measured nitrite in food samples.