Different configurations of carbon electrochemical sensors based on diamond nanoparticles for the simultaneous detection of phenolic compounds

In this work, we report the development of two different configurations of electrochemical carbon-based sensors for the simultaneous determination of phenolic compounds, namely hydroquinone, catechol, and resorcinol, which are harmful to human health and commonly found in the environment as a result of industrial discharges. In a first approach, we used diamond nanoparticles (DNPs) to modify the surface of a glassy carbon electrode to take advantage of their catalytic properties together with their electrical conductivity, high surface area and chemical stability. In a second approach, we extrapolated the developed electrochemical sensor to a low-cost device based on a carbon paper electrode modified with diamond nanoparticles. The aim of assaying this second configuration is to test whether it is possible to carry out the simultaneous determination of these phenols employing this flexible and low-cost substrate. Both configurations were morphologically characterized by scanning electron microscopy and atomic force microscopy. We have evaluated by cyclic voltammetry the responses of the glassy carbon and carbon paper electrodes in their bare or diamond nanoparticles-modified forms. The presence of diamond nanoparticles improves the sensitivity and peak separation, enabling the resolution of the three peaks. The overlapping of DNP surface unsaturated bond orbitals, which leads to the formation of discrete electronic states within the diamond's band gap, explains the conductivity and electrocatalytic properties of this nanomaterial. Its presence on the electrode also increases the surface area available for detection. Using the differential pulse voltammetry technique, we have obtained detection and quantification limits in the range of 1.8–8.5 μM and 6.0–28 μM, respectively, with wide linear concentration ranges. Furthermore, reproducibility (expressed as RSD) was between 4.8 % and 7.0 % and accuracy values, in terms of relative error, were below 8.0 %. Furthermore, the DNP-modified carbon paper sensor exhibits higher sensitivity than the glassy carbon-based sensor. To assess the electrochemical sensor applicability, a real river water sample was analysed, yielding recovery percentages between 90 % and 110 %. • Two simple configurations of electrochemical sensors based on diamond nanoparticles. • The presence of diamond nanoparticles improves the sensitivity and resolution. • Simultaneous analysis of phenolic compounds which can be harmful for humans.