An Electrochemical Sensor Based on Carbon Paper Modified with Graphite Powder for Sensitive Determination of Sunset Yellow and Tartrazine in Drinks

Abstract

The paper describes the development of an electrochemical sensor to be used for the determination of synthetic food colorants such as Sunset Yellow FCF (SY) and Tartrazine (TZ). The sensor is a carbon paper (CP) electrode, manufactured by using hot lamination technology and volume modified with fine-grained graphite powder (GrP). The sensor (GrP/CP) was characterized by scanning electron microscopy, energy dispersive spectrometry, electrochemical impedance analysis, cyclic, linear sweep and differential pulse voltammetry. The mechanism of SY and TZ electrochemical oxidation on GrP/CP was studied. The developed sensor has good electron transfer characteristics and low electron resistance, high sensitivity and selectivity. Applying the differential pulse mode, linear dynamic ranges of 0.005-1.0 μM and 0.02-7.5 μM with limits of detection of 0.78 nM and 8.2 nM for SY and TZ, respectively, were obtained. The sensor was used to detect SY and TZ in non-alcoholic and alcoholic drinks. The results obtained from drink analysis prove good reproducibility (RSD ≤ 0.072) and accuracy (recovery 96-104%).

Keywords: Sunset Yellow; Tartrazine; carbon paper; carbon veil; electrochemical sensor; food colorants; graphite powder; modified electrode; soft and alcoholic drinks; voltammetry.

Figure 1

Structural formulas of SY and TZ.

Figure 2

SEM images of the bare CP (a) and the CP modified with different carbon materials: MWCNTs (b), CB (c), GR (d) and GrP (e).

Figure 2

SEM images of the bare CP (a) and the CP modified with different carbon materials: MWCNTs (b), CB (c), GR (d) and GrP (e).

Figure 3

Cyclic voltammograms of 10 μM SY and TZ on the bare CP electrode (b) and the CP electrodes modified with GR (a), MWCNTs (c), CB (d), GrP (e). Supporting electrolyte: phosphate buffer solution pH 5, ν = 50 mV s⁻¹.

Figure 4

Dependence of oxidation peak current of 10 µM SY and TZ on the quantity of graphite powder immobilized on the CP electrode.

Figure 5

Experimental (points) and fitted (lines) Nyquist plots for CP and GrP/CP electrodes in 0.1 M KCl containing 0.01 M [Fe(CN)₆]^3−/4− (a). Bode plots (b). Frequency (ω) range 0.1 Hz–100 kHz at polarization potential of 0.2 V. Inserts: Randles equivalent cells.

Figure 6

The plot of I_pa vs. ν^1/2 for CP and GrP/CP electrodes.

Figure 7

Linear sweep voltammograms of 10 μM SY and 10 μM TZ on GrP/CP electrode in phosphate buffer solution at different pH at the scan rate of 50 mV s⁻¹ (a), the effects of pH on the anodic peak potentials (b) and anodic peak currents (c).

Figure 8

Linear sweep voltammograms of SY and TZ (10 µM each) on GrP/CP electrodein phosphate buffer solution pH 5 at different potential scan rates: 25, 50, 75, 100, 125, 150, 200, 250, 300 mV s⁻¹ (a). Plots I_pa = f(ν) for SY (b), I_pa = f(ν^1/2) for TZ (c) and ln I_pa = f(ln ν) (d), E_pa = f(ln ν) for TZ (e).

Figure 8

Linear sweep voltammograms of SY and TZ (10 µM each) on GrP/CP electrodein phosphate buffer solution pH 5 at different potential scan rates: 25, 50, 75, 100, 125, 150, 200, 250, 300 mV s⁻¹ (a). Plots I_pa = f(ν) for SY (b), I_pa = f(ν^1/2) for TZ (c) and ln I_pa = f(ln ν) (d), E_pa = f(ln ν) for TZ (e).

Figure 9

Electroconversion of SY and TZ.

Figure 10

Differential pulse voltammograms of different SY concentrations (0.005, 0.01, 0.05, 0.1, 0.2, 0.35, 0.5, 0.7, 0.9, 1.0 µM) in the presence of 0.5 μM TZ (a) and different TZ concentrations (0.02, 0.04, 0.08, 0.3, 0.8, 3.0, 5.0, 7.5 µM) in the presence of 0.2 μM SY (b). Inserts: linear dependences of anodic peak current vs. dye concentration. Supporting electrolyte: phosphate buffer solution pH 5, accumulation time 180 s.