Sustainable materials have been widely used in the development of new materials, such as in electrochemical devices [1]. Thin films based on greener sources, such as propolis, allow the development of environmentally friendly biocomposites. Hence, we have proposed the use of a biofilm-based on propolis for the stable and homogeneous immobilization of carbon nanotubes (CNTs), which increased the electrical conductivity of the GCE base electrode by almost 500 thousand times. The biofilm was used for the spontaneous anchoring of Ni2+ ions and electrochemical synthesis of nickel oxide-hydroxide (NiOOH). The proposed electrode was used for the simultaneous determination of total sugars (glucose, fructose, and sucrose) and hydroxymethylfurfural (HMF). The monitoring of HMF in the presence of total sugars provides complete information about the honey, allowing to determine if the sample has been adulterated or degraded. The sensor was able for monitoring the three different sugars (non-selective) at around +0.50 V (vs. Ag|AgCl|3.0 mol L−1 KCl) [2]. On the other hand, the determination of these species did not influence the determination of HMF that was monitored by the reduction process around −1.35 V (vs. Ag|AgCl|3.0 mol L−1 KCl) [3]. The sensor was sensitive to successive additions of all species simultaneously evaluated. Therefore, the quantification of a simulated honey sample was performed by linear sweep voltammetry technique at 100 mV s−1 in 0.1 mol L−1 NaOH. Linear responses between current and the concentrations of HMF and sugars were observed at 0.25–11 mmol L−1 and 0.05–11 mmol L−1, respectively. Limits of detection of 0.18 and 0.038 mmol L−1 were obtained for HMF and total sugars, respectively. This analytical efficacy of the proposed sensor qualifies this strategy for the development of eco-friendly sensors for the quality control of honey samples.

Greener biocomposite thin film based on propolis for simultaneous determination of sugars and hydroxymethylfurfural in honey samples

ACS Spring 2022

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