Green method for glucose determination using microfluidic device with a non-enzymatic sensor based on nickel oxyhydroxide supported at activated biochar.

This paper reports the use of nickel ions supported at activated biochar carbon paste electrode (NiAB-CPME) coupled in a microfluidic thread-based electroanalytical device (μTED) for non-enzymatic glucose determination. Biochar was initially prepared from castor oil cake at 400 °C and activated by HNO refluxing. Activation process promoted an increase of functional groups, surface area and porosity in comparison to precursor biochar. Activated biochar (AB) has shown an excellent performance to spontaneous preconcentration of Ni(II) ions. In alkaline conditions a stable voltammetric profile associated to Ni(OH)/NiOOH redox pair was verified and a significant catalytic effect was observed in presence of glucose which was used for its monitoring. Microfluidic device was assembled at a plastic platform printed using 3D printer being easy to construction using low cost materials. Non-enzymatic amperometric glucose sensor coupled in μTED showed a good repeatability of 3.84% for successive injections of glucose (n = 10), a constant flow rate of 1.11 µL s and an analytical frequency of 61 injections per hour. A linear dynamic range (LDR) from 5.0 to 100.0 µmol L, limit of detection (LOD) of 0.137 µmol L and limit of quantification (LOQ) 0.457 µmol L glucose were obtained. The proposed device was applied to glucose determination in real biological samples of human saliva and blood serum. Finally, the method was considered a green analytical procedure with Eco-Scale score of 81.