# Nitrite: From Application to Detection and Development
## 5 Electrochemical Sensors

Table 2: Definitions and explanations of material or equipment in Table 1.  
ticles loaded on carbon black and tapioca for modified glassy carbon electrodes. The fabricated sensor was used for the electrochemical determination of nitrite using differential pulse voltammetry with a linear range of 5.0-1000 \(\upmu\)mol L\({}^{-1}\) and a detection limit of 1.24 \(\upmu\)mol L\({}^{-1}\). The proposed method was applied to the detection of target analytes in environmental and food samples and was sensitive to the electrochemical sensing of nitrite [99]. The majority of electrochemical sensor electrodes are made up of electrodes made of nanocomposites. Researchers prepared and modified gold nanorods (AuNRs) and tungsten disulfide (WS\({}_{2}\)) nanocomposites on the surface of a carbon ionic liquid electrode (CILE). Hemoglobin (Hb) with peroxidase activity was further immobilized on the electrode surface, and a novel modified electrode (Nafion/Hb/AuNRs-WS\({}_{2}\)/CILE) was prepared, which has high conductivity and good biocompatibility [100]. Furthermore, well-dispersed and uniformly sized silver nanoparticles dispersed on polyaniline/reduced graphene oxide nanocomposites were prepared by a biphasic method in the absence of external oxidants. With a wider peak separation window, they can be used for the electrochemical detection of two analytes in water sources [101]. Layered FeTMPyP/Sr\({}_{2}\)Nb\({}_{3}\)O\({}_{10}\) nanocomposites have been successfully synthesized by embedding positively charged iron 5,10,15,20-tetrakis(N-methylpyridin-4-yl) porphyrin (FeTMPyP) in KSr\({}_{2}\)Nb\({}_{3}\)O\({}_{10}\). The results showed that FeTMPyP/Sr\({}_{2}\)Nb\({}_{3}\)O\({}_{10}\) exhibited excellent performance for the electrochemical oxidation of nitrite. In addition, this nanocomposite exhibited good stability and excellent interference resistance [102]. Novel bismuth molybdate@polydopamine-Au nanocomposites (Bi\({}_{2}\)MoO\({}_{6}\)@PDA-Au) were synthesized, which exhibited good reproducibility, reusability, long-term stability, fast response time, and anti-interference properties [103]. Au@CQDs-MXene nanocomposites with good electrical conductivity and electrocatalysis were prepared using MXene (two-dimensional transition metal carbides, nitrides) with good electrical conductivity as the immobilized matrix [104]. An electrochemical sensor for nitrite based on in situ prepared copper oxide nanoparticles modified carbon cloth (Cu NPs/CC) was prepared with simple and efficient detection [105]. A novel and sensitive surface-enhanced Raman scattering (SERS) platform for silver-coated nanofibers was developed, and silver nanoparticles (NPs) were assembled on nanofibers for the first time using electrospray technology [106]. Additionally, the researchers prepared a novel non-enzymatic nitrite (NO\({}_{2}\)\({}^{-}\)) electrochemical sensor based on Au-poly(thionine)-tin oxide/graphene nanosheets (Au-PTH/SGN) nanocomposites [107]. Furthermore, AuNP/MnOx-VOx/ERGO electrode was employed for the determination of hydrazine and nitrite in river water and food samples, which showed recoveries ranging from 91.0% to 113.0% [108]. In the pursuit of higher sensitivity, better stability, wider linear range, and excellent selectivity of nitrite chemical sensors, the focus of research has shifted to the nanomaterials used. Therefore, more and more developments in these nanomaterials have been made in recent years. A simple and highly selective electrochemical sensor based on carbonized lotus root (CLS) has been developed, and the intrinsic structure of this natural biomass is expected to be used to design porous carbon for electrochemical sensors [109]. One-dimensional honeycomb carbon nanofibers (HCNFs) were synthesized by electronic techniques with good properties and recyclability [110]. A UCL nano sensor was designed, which is expected to be used in the future as a technique for detecting nitrite in food products [111].