Non-enzymatic determination of purine nucleotides using a carbon dot modified glassy carbon electrode

Abstract

Selective and sensitive determination of one of the purine nucleotides, inosine (INO) using a low cost carbon dot (CD) modified glassy carbon (GC) electrode in 0.2 M phosphate buffer solution (pH 7.2) was demonstrated in this paper. Initially, the CDs were prepared by a one-step alkali assisted ultrasonic chemical method using glucose as a precursor. The successful formation of CDs was confirmed by UV-visible, FT-IR, fluorescence and HR-TEM techniques. The HR-TEM images showed that the average particle size of CDs was found to be 1.64 nm. Further, the prepared CDs were directly attached on the GC electrode and it was characterized by attenuated total reflectance (ATR)-FTIR, scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV) and electrical impedance spectroscopy (EIS) techniques. The SEM images showed that the size of the CDs was increased from 1.64 to 39.4 nm after being attached on the GC surface. Then, the modified electrode was utilized for the selective and sensitive determination of INO at physiological pH. CD/GC showed two-fold higher oxidation current for INO than the bare GC electrode. The amperometric current response was increased linearly with increasing INO concentration in the dynamic range of 50 × 10⁻⁹ to 20 × 10⁻⁶ M and the limit of detection (LOD) was found to be 8.3 × 10⁻⁹ M (S/N = 3). It was further used to selectively detect INO in the presence of 50-fold higher concentrations of uric acid and xanthine. The practical application of the proposed modified electrode was demonstrated by determining INO in human blood serum and urine samples.