An electrochemical biosensor for determination of ascorbic acid by cobalt (II) phthalocyanine–multi-walled carbon nanotubes modified glassy carbon electrode

Cobalt (II) phthalocyanine–multi-walled carbon nanotubes (CoPc–MWNTs) were synthesized and characterized by energy dispersive X-ray spectroscopy (EDX) and transmission electron microscopy (TEM). The cobalt (II) phthalocyanine–multi-walled carbon nanotubes modified glassy carbon (CoPc–MWNTs/GC) electrode was prepared using the drop coating method. The electrocatalytic performance of the chemically modified electrode was investigated for ascorbic acid (AA) oxidation. Our results demonstrate that the modified electrode has excellent electrocatalytic activity towards the oxidation of AA in 0.1 M phosphate buffer solution (PBS, pH 7.0). The oxidation potential of AA was negatively shifted to 0.19 V [vs. saturated calomel electrode (SCE)]. The biosensor tolerated a wide linear concentration range for AA, from 1.0 × 10−5 M to 2.6 × 10−3 M (R = 0.9991), with a detection limit of 1.0 × 10−6 M (S/N = 3). The CoPc–MWNTs modified glassy carbon electrode has several excellent properties, including a fast response time, high reproducibility and stability.