Electrochemical determination of melatonin using disposable self-adhesive inked paper electrode

Melatonin is a hormone that affects sleep-wake cycles and plays a role in the understanding of neuronal disorders and has excellent potential for therapeutical applications in infectious diseases, becoming an important target of chemical analysis. In this context, we report the development of an electrochemical device comprising a self-adhesive electrode based on a graphite-automotive varnish (Gr-AV) mixture as a conductive material to produce a printable ink applied over a paper adhesive easily transferred to a polyethylene terephthalate substrate. The Gr-AV electrode presented a high electrochemically active surface area which showed to be suitable for melatonin oxidation. The association of the device alongside a square-wave voltammetry method offered a linear behavior in the concentration range from 10.0 to 100.0 µmol L−1, a limit of detection of 0.49 µmol L−1, as well as presenting exciting recovery and relative standard deviation over samples analysis. The results showed the valid application of the device for the determination of melatonin in biological samples, pharmaceutical formulations, and its potential for point-of-care analysis.