A class-selective and reliable electrochemical monosaccharide index in honeys, as determined using nickel and...

The electrochemical detection of sugars is favored by the electrocatalytic effects of copper and nickel, which allow their detection with high sensitivity and without the need for derivatization. Also, novel nanotechnological tools known as metallic nanowires (NWs) may offer new possibilities for sensing, since their large active surfaces allow greatly enhanced sensitivity. In this work, nickel (NiNWs) and nickel-copper (Ni-CuNWs 50:50 w/w) nanowires were synthesized by electroplating using an alumina template, and characterized by scanning electronic microscopy (SEM), transmission electronic microscopy (TEM), and energy-dispersive X-ray spectrometry (EDS). Using an alumina template of 200 nm, and under the controlled deposition of 45 C of charge, both of these NWs were obtained with lengths of about 7 μm and widths of about 300 μm. EDS analysis confirmed that the percentage of Ni in the NiNWs was 97%, and the percentages of Ni and Cu in the Ni-CuNWs were 50.6% and 49.4%, respectively. Both of the electrosynthesized NW exhibited enhanced electrocatalytic properties (and therefore improved detection sensitivity) toward the target sugars. Analytical performance was then evaluated by analyzing ten target honeys, utilizing a simplified calibration strategy that employed a glucose:fructose mixture as the standard. Repeatability was excellent when calibration (RSDs ≤ 5%) and sample analysis (RSDs ≤ 6%) protocols were performed. The total sugar content obtained by the electrochemical approach was compared with that obtained using a HPLC-RI (refractive index) method. The novel method gave low systematic errors, revealing that it afforded very accurate results. Also, a high throughput was achieved, as 60 samples were processed in about 25 min (yielding a rate of 2 samples min(-1)) on a board containing just one electrode, without any loss of performance. While both electrosynthesized NWs exhibited good analytical performance, the NiNWs were judged to be the most suitable for use in a sensor because of their easy preparation, stability, and magnetic properties. Nanowire-based disposable screen-printed detectors that are strategically connected to miniaturized instrumentation represent a novel approach that could be used in standard labs.