A simple ultrasensitive electrochemical sensor for simultaneous determination of homovanillic acid and vanillylmandelic acid in human urine based on MWCNTs-Pt nanoparticles as peroxidase mimics

Abstract In this paper, a novel electrochemical sensor based on the combination of multi-walled carbon nanotubes and platinum nanoparticles (MWCNTs-PtNPs) as peroxidase mimics was developed for simultaneous detection of homovanillic acid (HVA) and vanillylmandelic acid (VMA) in human urine with excellent resolution, which were separated about 200 mV apart by electrochemistry. The modified electrode was investigated by different methods including electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Electrochemical studies show that MWCNTs-PtNPs modified GCE has an excellent separation performance for HVA and VMA with little overlapping, showing significant peroxidase mimetic oxidation catalysis. Under optimal conditions, the sensor exhibits good linear responses for HVA and VMA in the range of 2 × 10−7 mol L−1 to 8 × 10−5 mol L−1 and 5 × 10−7 mol L−1 to 8 × 10−5 mol L−1 with the detection limits of 8 × 10−8 mol L−1 for HVA and 1.73 × 10−7 mol L−1 for VMA (S/N = 3), respectively. Furthermore, MWCNTs-PtNPs/GCE was successfully applied to the simultaneous determination of HVA and VMA in human urine samples.