Determination of trace amounts of ochratoxin A in different food samples based on gold nanoparticles modified carbon paste electrode

Abstract

In the present study, a carbon paste electrode chemically modified with gold nanoparticles was used as a sensitive electrochemical sensor for determination of ochratoxin A. The differential pulse voltammetric method was employed to study the behavior of ochratoxin A on this modified electrode. The effect of variables such as percent of gold nanoparticles, pH of sample solution, accumulation potential and time on voltammogram peak current were optimized. The proposed electrode showed good oxidation response for ochratoxin A in 0.1 mol L(-1) PBS (pH 7.2) and the peak potential was about +0.8 V (vs. Ag/AgCl). The peak current increased linearly with the ochratoxin A concentration in the range of 0.5-100 nM. The detection limit was found to be 0.2 nM and the relative standard deviation was 6.2 % (n = 7). The method has been applied to the determination of ochratoxin A in cereal derived products such as breakfast cereals, cereal-based baby foods and beer samples.

Keywords: Gold nanoparticles; Modified carbon paste electrode; Ochratoxin a determination; Real samples analysis.

Fig. 1

TEM image of a) gold nano particles and b) gold nanoparticles/carbon paste composite

Fig. 2

Differential pulse anodic stripping voltammograms of 100 nM OTA after closed circuit accumulation: a CPE-GNP and, b bare CPE. Experimental conditions: stripping medium: 0.1 M PBS (pH = 7.2), deposition potential: +0.5 V, deposition time: 180 s, scan rate: 50 mV s⁻¹, pulse amplitude: 50 mV s⁻¹ and pulse time: 4 s

Fig. 3

Schematic representation of the oxidation reaction of ochratoxin

Fig. 4

Differential pulse anodic stripping voltammograms in a solution containing OTA; a 0.5 nM, b 1.0 nM, c 5.0 nM, d 20.0 nM, e 50.0 nM, f 75.0 nM, g 100.0 nM. Experimental condition: supporting solution: PBS, deposition potential: +0.5 V, deposition time: 180 s, scan rate: 50 mV s⁻¹, pulse amplitude: 50 mV s⁻¹and pulse time: 4 s. inset: Plot of I(μA) vs. OTA concentrations