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

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.