Construction of an Electrochemical Sensor Based on Carbon Nanotubes/Gold Nanoparticles for Trace Determination of Amoxicillin in Bovine Milk

Abstract

In this work, a novel electrochemical sensor was fabricated for determination of amoxicillin in bovine milk samples by decoration of carboxylated multi-walled carbon nanotubes (MWCNTs) with gold nanoparticles (AuNPs) using ethylenediamine (en) as a cross linker (AuNPs/en-MWCNTs). The constructed nanocomposite was homogenized in dimethylformamide and drop casted on screen printed electrode. Field emission scanning electron microscopy (FESEM), energy dispersive X-Ray (EDX), X-Ray diffraction (XRD) and cyclic voltammetry were used to characterize the synthesized nanocomposites. The results show that the synthesized nanocomposites induced a remarkable synergetic effect for the oxidation of amoxicillin. Effect of some parameters, including pH, buffer, scan rate, accumulation potential, accumulation time and amount of casted nanocomposites, on the sensitivity of fabricated sensor were optimized. Under the optimum conditions, there was two linear calibration ranges from 0.2-10 µM and 10-30 µM with equations of Ipa (µA) = 2.88C (µM) + 1.2017; r = 0.9939 and Ipa (µA) = 0.88C (µM) + 22.97; r = 0.9973, respectively. The limit of detection (LOD) and limit of quantitation (LOQ) were calculated as 0.015 µM and 0.149 µM, respectively. The fabricated electrochemical sensor was successfully applied for determination of Amoxicillin in bovine milk samples and all results compared with high performance liquid chromatography (HPLC) standard method.

Keywords: AuNPs; MWCNTs; amoxicillin; bovine milk; electrochemical sensor; ethylediamine.

Figure 1

Chemical structure of amoxicillin.

Scheme 1

Bulk scale synthetic illustration of AuNPs/en-MWCNTs nanocomposite using ethylenediamine as a cross linker.

Figure 2

FESEM Images of (a) MWCNTs film; and (b) AuNPs/en-MWCNTs films.

Figure 3

EDX Spectra of AuNPs/en-MWCNTs nanocomposites. Inset: XRD Spectra of the synthesized nanocomposites.

Figure 4

Cyclic voltammograms of 10 µM Amoxicillin on bare SPE and after modification with MWCNTs and AuNPs/en-MWCNTs in phosphate buffer (pH 4.0).

Figure 5

Effect of accumulation potential on the oxidation peak current of Amoxicillin on the surface of AuNPs/en-MWCNTs/SPE. Amoxicillin, 10 µM; Phosphate buffer, pH 7.0; Accumulation time, 60 s.

Figure 6

Effect of accumulation time on the oxidation peak current of Amoxicillin on the surface of AuNPs/en-MWCNTs/SPE. Amoxicillin, 10 µM; Phosphate buffer, pH 7.0; Accumulation potential, −0.4 V.

Figure 7

Adsorptive stripping response of different concentration of Amoxicillin at the modified electrode. Inset: Calibration curve of the peak current versus concentration of Amoxicillin in the presence of 0.1 M Phosphate buffer (0.1 M, pH 7.0); accumulation time, 180 s; accumulation potential, −0.4 V; and scan rate, 0.1 V·s⁻¹.