Abstract:
In this study, nitrogen defect-rich graphitic carbon nitride was synthesized and used to
modify glassy carbon electrode for the electrochemical determination of tryptophan.
Nitrogen defect-rich graphitic carbon nitride was prepared by thermally polymerizing
graphitic-carbon nitride under inert conditions. The obtained nitrogen defect-rich
graphitic carbon nitride was characterized by X-ray diffraction, Fourier transform
infrared spectroscopy, X-ray photoelectron spectroscopy
and scanning electron
microscope. Cyclic voltammetry was used to further analyze the electrochemical
properties of bare glassy carbon electrode, graphitic-carbon nitride modified glassy
carbon electrode, and nitrogen defect-rich graphitic carbon nitride modified glassy carbon
electrode. It was found that nitrogen defect-rich graphitic carbon nitride modified glassy
carbon electrode exhibited superior electrocatalytic oxidation, enhanced anodic peak
current, and less overpotential towards tryptophan as compared to graphitic-carbon
nitride modified glassy carbon electrode and bare glassy carbon electrode. Experimental
parameters such as, scan rate, effect of pH, temperature of polymerization of nitrogen
defect-rich graphitic carbon nitride were optimized. The suggested electrode showed
excellent repeatability, reproducibility, and a low detection limit. Tryptophan in a milk
sample was successfully determined using the produced nitrogen defect-rich graphitic
carbon nitride modified glassy carbon electrode with a percentage recovery in the range
of 97.0-108%, satisfactory recovery obtained from the demonstrated electrochemical
sensor. Under the optimum experimental conditions, the oxidation peak currents had
good linear relationship with Tryptophan concentrations in the range of 0.02- 0.20 μM at
pH 3.0 and a limit of detection of about 0.0034 μM (3σ/m). In addition, the obtained
sensor showed good sensitivity, favorable repeatability, and long term stability. Finally,
the proposed electrochemical method has been successfully applied for the determination
of Trp in real samples with satisfactory results.
