Amperometric sensor for glucose based on electrochemically polymerized tetraruthenated nickel-porphyrin

Glassy carbon and gold electrodes were modified with tetraruthenated Ni-porphyrin by electropolymerization in alkaline medium and characterized by cyclic voltammetry, UV-vis spectroscopy and MAC-mode scanning probe microscopy (SPM). The half-wave potentials and current intensities associated with the NiIII/NiII process were strongly pH-dependent. The modified electrodes were successfully employed as sensors for glucose in alkaline medium, based on the catalytic activity of the NiIII/NiII centers. Glucose quantification was carried out by means of cyclic voltammetry or amperometry coupled to batch injection analysis (BIA). The BIA-amperometry technique revealed more efficiency than cyclic voltammetry, lowering the detection limit to 3.6 × 10−7 mol L−1, and providing a larger, linear working range (2.5 × 10−6 to 1.0 × 10−3 mol L−1), better repeatability (RSD = 1.1% for 25 injections of 2.5 × 10−5 mol L−1), and higher sampling frequency (60 samples h−1). The new sensor was successfully employed for the analysis of glucose in parentheral nutrition solutions and the results were in good agreement with the ones obtained by spectrophotometry, utilizing a modified Benedict's test.