Electrochemical sensors for improved detection of paraquat in food samples: A review

Paraquat (1,10-dimethyl-4,40-dipyridinium chloride), also known as methyl viologen, is widely used as a quaternary ammonium herbicide (broadleaf weed killer) all over the world owing to its excellent effect in plant cells for crop protection and horticultural use. However, it is dangerous because of its high acute toxicity even at low concentrations. Its detection in the environment is therefore necessary. As a consequence of its widespread usage, it causes genotoxic, teratogenic as well as other environmental and ecological adverse impacts. Exposure to PQ leads to a high mortality rate because no specific drug is effective for treatment. Excessive consumption of PQ can cause cellular damage and necrosis in the brain, heart, lungs, liver, and kidneys. The diversity and sensitivity of the analyses currently required have forced the experimenter to use more advanced and efficient techniques, which can provide qualitative and quantitative results in complex environments. Electrochemical methods generally meet these criteria while offering other advantages to achieve excellent accuracy and fast handling. This paper provides an overview of the determination of PQ using electrochemical methods combined with several modified electrodes in food samples, including milk, apple juice, tomato juice, and potato juice. Emphasis was placed on the most relevant modifiers used to generate high selectivity and sensitivity such as noble metals, metallic nanoparticles, polymers, biomolecules, clay, and apatite minerals. Comprehensively, it is strongly convincing that the synergy between the sensor substrate and the modifier architecture gives the electrodes a high capacity to detect paraquat in complex matrices such as food. In line with the context, information's on the mechanism of electrooxidation or reduction of PQ has been reported with the discussion of some future prospects and some insights. To the best of our knowledge, there is no review article relating the electrochemical determination of paraquat.