Ion-selective electrodes based on laser-induced graphene as an alternative method for nitrite monitoring.

Abstract

Nitrite is an important food additive for cured meats; however, high nitrite levels pose adverse health effects to humans. Hence, monitoring nitrite concentration is critical to comply with limits imposed by regulatory agencies. Laser-induced graphene (LIG) has proven to be a scalable manufacturing alternative to produce high-performance electrochemical transducers for sensors. Herein, we expand upon initial LIG studies by fabricating hydrophilic and hydrophobic LIG that are subsequently converted into ion-selective sensors to monitor nitrite in food samples with comparable performance to the standard photometricmethod (Griess method). The hydrophobic LIG resulted in an ion-selective electrode with improved potential stability due partly to a decrease in the water layer between the electrode and the nitrite poly(vinyl) chloride-based ion-selective membrane. These resultant nitrite ion-selective sensors displayed Nernstian response behavior with a sensitivity of 59.5mV dec-1, a detection limit of 0.3 ± 0.1mg L-1(mean ± standard deviation), and a broad linear sensing range from 10-5 to 10-1M, which was significantly larger than currently published nitrite methods. Nitrite levels were determined directly in food extract samples of sausage, ham, and bacon for 5min. These sensor metrics are significant as regulatory agencies limit nitrite levels up to 200mg L-1in finished products to reduce the potential formation of nitrosamine (carcinogenic compound). These results demonstrate the versatility of LIG as a platform for ion-selective-LIG sensors and simple, efficient, and scalable electrochemical sensing in general while demonstrating a promising alternative to monitor nitrite levels in food products ensuring regulatory compliance.