Electrochemical determination of dopamine and uric acid using a glassy carbon electrode modified with a composite consisting of a Co(II)-based metalorganic framework (ZIF-67) and graphene oxide

A composite was prepared from a Co(II)-based zeolitic imidazolate framework (ZIF-67) and graphene oxide (GO) by an in situ growth method. The material was electrodeposited on a glassy carbon electrode (GCE). The modified GCE was used for the simultaneous voltammetric determination of dopamine (DA) and uric acid (UA), typically at working potentials of 0.11 and 0.25 V (vs. SCE). The morphology and structure of the nanocomposite were characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy and X-ray diffraction. The modified electrode exhibits excellent electroanalytical performance for DA and UA owing to the synergistic effect of the high electrical conductivity of GO and the porosity of ZIF-67. By applying differential pulse voltammetry, a linear response is found for DA in the 0.2 to 80 mu M concentration range, and for UA between 0.8 and 200 mu M, with detection limits of 50 and 100 nM (at S/N = 3), respectively. Further studies were performed on the effect of potential interferents, and on electrode stability and reproducibility. The modified GCE was applied to the simultaneous detection of DA and UA in spiked human urine and gave satisfying recoveries.