Food contamination with heavy-metal ions and nitrites poses a serious threat to human health. Consequently, the development of fast and sensitive platforms for detecting these contaminants is urgently needed. In this study, a novel sensing platform was developed by integrating carbon nanotubes generated by the pyrolysis of waste masks (WMCNTs) with ZIF-8 for the simultaneous detection of Cd2+, Pb2+, and nitrite. Specifically, the electronic structure of the WMCNT backbone was modulated by doping with B and N atoms. Nanoporous ZIF-8 was then grown in-situ on its surface to produce composites with enhanced electrical conductivities and large specific surface areas. This modification provided more active sites for the attachment of heavy-metal ions and nitrites. Under optimized conditions, the sensing platform exhibited a wide linear range with the Pb2+, Cd2+, and NO2 − limits of detection of 2.68, 12.12, and 5.94 μM, respectively. Notably, the sensing platform demonstrated excellent anti-interference capabilities and effectively detected nitrites and heavy-metal ions in pickled foods.

Upcycling of waste masks into carbon nanotubes combined with ZIF-8 for the detection of heavy-metal ions and nitrite
    Abstract
        Graphical abstract
    1 Introduction
    2 Experimental section
        2.1 Instruments and reagents
        2.2 Preparation of metal catalysts
        2.3 Preparation of WMCNTs
        2.4 Preparation of B, N-WMCNTs
        2.5 Preparation of ZIF-8@B, N-WMCNTs
        2.6 Fabrication of the sensing platform
        2.7 Electrochemical measurement
    3 Results and discussion
        3.1 Characterization of materials
        3.2 Electrochemical characterization
        3.3 Optimization of experimental conditions
        3.4 Electrochemical detection of Pb2+, Cd2+, and NO2−
        3.5 Repeatability, reproducibility, and interference studies
        3.6 Actual sample evaluation
    4 Conclusions
    Acknowledgements 
    References

• Tong Han(Interdisciplinary Program of Biological Functional Molecules, MOE Key Laboratory of Natural Medicines of the Changbai Mountain, Department of Chemistry, Yanbian University, Park Road 977, Yanji 133002, Jilin, People’s Republic of China)
• Ying‑Ai Piao(Analysis and Test Center, Yanbian University, Park Road 977, Yanji 133002, Jilin, People’s Republic of China)
• Biao Jin(Analysis and Test Center, Yanbian University, Park Road 977, Yanji 133002, Jilin, People’s Republic of China)
• Long‑Yue Meng(Department of Environmental Science, College of Geography and Ocean Sciences, Yanbian University, Park Road 977, Yanji 133002, Jilin, People’s Republic of China) Corresponding author