Zeolitic imidazolate frameworks (ZIFs) along with carbon nanofibers and polyaniline composite have been explored as an electrochemical sensing platform in nitrite measurement at trace level. Owing to their topology, high surface area and porous structure, these metal–organic frameworks (MOFs) find widespread utility in different application domains. Nitrites are widely used as preservatives in dairy, meat products, and packaged food stuffs. They form N-nitrosamines, which are potential carcinogens and cause detrimental health effects. These ZIF-based MOFs along with carbon nanofibers and polyaniline have emerged as an efficient electrochemical sensing material. The composite has been characterized by X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and BET surface area studies. The electrochemical performance of the composite has been evaluated by forming as a thin film of composite on the surface of glassy carbon electrode and studying its impedance as well as electrochemical sensing behavior. The sensor exhibited good analytical response in nitrite measurement with a limit of detection of 8.1 μM. The developed sensing platform has been successfully applied to quantify the nitrite levels from water samples. The results obtained are in good agreement with the results of standard protocol.

ZIF-8CNFsPANI composite as an electrochemical platform in trace-level nitrite sensing
    Abstract
        Graphical abstract
    1 Introduction
    2 Experimental section
        2.1 Chemicals and reagents
        2.2 Materials and methods
        2.3 Synthesis of ZIF-8 crystals
        2.4 Synthesis of CNFPANI
        2.5 Synthesis of CNFPANIZIF-8 composite
        2.6 Fabrication of sensor
    3 Results and discussion
        3.1 FTIR study
        3.2 Raman study
        3.3 XRD study
        3.4 SEM and EDS study
        3.5 XPS study
        3.6 BET surface area study
        3.7 Electrochemical characterization
            3.7.1 EIS study
            3.7.2 Electrochemical behavior of CNFPANIZIF-8 composite-modified electrode in the presence of nitrite
            3.7.3 Optimization study
                3.7.3.1 Effect of scan rate 
                3.7.3.2 Effect of pH 
                3.7.3.3 Effect of pulse amplitude and pulse frequency 
                3.7.3.4 Effect of deposition time and deposition potential 
            3.7.4 Calibration plot
            3.7.5 Stability and reproducibility
            3.7.6 Effect of foreign ions
            3.7.7 Application study
    4 Conclusions
    Acknowledgements 
    References

• Suma B. Patri(Department of Studies in Chemistry, Bengaluru City University, Central College Campus, Bengaluru 560001, India)
• Supritha M. Karekuladh(Department of Studies in Chemistry, Bengaluru City University, Central College Campus, Bengaluru 560001, India)
• Pandurangappa Malingappa(Department of Studies in Chemistry, Bengaluru City University, Central College Campus, Bengaluru 560001, India)