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

Nitrite (NO2 - ) 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@Bi2 S3 MS/SPE), and integrated with a smartphone-interfaced potentiostat to develop a portable, electrochemical nitrite sensor. NanoPd@Bi2 S3 MS was prepared by the hydrothermal reduction of a Bi2 S3 MS and Pd2+ dispersion and drop cast on the SPE. The nanoPd@Bi2 S3 MS/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.