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. 2022 Dec 11;14(24):5429.
doi: 10.3390/polym14245429.

Electropolymerized 4-Aminobenzoic Acid Based Voltammetric Sensor for the Simultaneous Determination of Food Azo Dyes

Guzel Ziyatdinova  1 , Maria Titova  1 , Rustam Davletshin  2
Affiliations

Electropolymerized 4-Aminobenzoic Acid Based Voltammetric Sensor for the Simultaneous Determination of Food Azo Dyes

Guzel Ziyatdinova et al. Polymers (Basel). .

Abstract

Electrochemical sensors with polymeric films as a sensitive layer are of high interest in current electroanalysis. A voltammetric sensor based on multi-walled carbon nanotubes (MWCNTs) and electropolymerized 4-aminobenzoic acid (4-ABA) has been developed for the simultaneous determination of synthetic food azo dyes (sunset yellow FCF and tartrazine). Based on the voltammetric response of the dyes' mixture, the optimal conditions of electropolymerization have been found to be 30-fold potential scanning between -0.3 and 1.5 V, at 100 mV s-1 in the 100 µmol L-1 monomer solution in phosphate buffer pH 7.0. The poly (4-ABA)-based electrode shows a 10.5-fold increase in its effective surface area and a 17.2-fold lower electron transfer resistance compared to the glassy carbon electrode (GCE). The sensor gives a sensitive and selective response to sunset yellow FCF and tartrazine, with the peak potential separation of 232 mV in phosphate buffer pH 4.8. The electrooxidation parameters of dyes have been calculated. Simultaneous quantification is possible in the dynamic ranges of 0.010-0.75 and 0.75-5.0 µmol L-1 for both dyes, with detection limits of 2.3 and 3.0 nmol L-1 for sunset yellow FCF and tartrazine, respectively. The sensor has been tested on orange-flavored drinks and validated with chromatography.

Keywords: 4-aminobenzoic acid; electrochemical sensors; electropolymerization; food analysis; modified electrodes; sunset yellow; tartrazine.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Food azo dyes structure: (a) Sunset yellow FCF; (b) Tartrazine.
Figure 2
Figure 2
Baseline-corrected differential pulse voltammograms of 10 µmol L−1 sunset yellow FCF and tartrazine in phosphate buffer pH 7.0: (a) at the bare GCE; (b) at the MWCNTs/GCE. Modulation amplitude is 50 mV, modulation time is 50 ms, potential scan rate is 20 mV s−1.
Figure 3
Figure 3
Oxidation currents of sunset yellow FCF and tartrazine mixtures of various concentrations at MWCNTs/GCE in phosphate buffer pH 7.0.
Figure 4
Figure 4
Cyclic voltammograms of 100 µmol L−1 4-ABA at the MWCNTs/GCE in phosphate buffer pH 7.0: (a) 1 scan; (b) 1–30 scans. The potential scan rate is 100 mV s−1.
Scheme 1
Scheme 1
4-ABA electropolymerization.
Figure 5
Figure 5
Effect of 4-ABA electropolymerization conditions on the oxidation currents of the 0.10 µmol L−1 mixture of sunset yellow FCF and tartrazine at the poly(4-ABA)/MWCNTs/GCE in phosphate buffer pH 7.0 in differential pulse mode: (a) Effect of scan number; (b) Effect of monomer concentration; (c) Effect of potential scan rate; (d) Effect of potential range.
Figure 6
Figure 6
Electrode surface morphology by scanning electron microscopy: (a) bare GCE; (b) MWCNTs/GCE; (c) Poly(4-ABA)/MWCNTs/GCE.
Figure 7
Figure 7
(a) Cyclic voltammograms of 1.0 mM hexacyanoferrate(II) ions in 0.1 M KCl at the bare GCE, MWCNTs/GCE and poly(4-ABA)/MWCNTs/GCE. The potential scan rate is 100 mV s−1; (b) Nyquist plot (experimental (points) and fitted (lines)) for bare GCE, MWCNTs/GCE and poly(4-ABA)/MWCNTs/GCE in the presence of 1.0 mmol L−1 hexacyanoferrate(II)/(III) ions in 0.1 mol L−1 KCl. E = 0.21 V; frequency range =10 kHz–0.04 Hz; amplitude = 5 mV.
Figure 8
Figure 8
Baseline-corrected differential pulse volammograms of 0.10 µmol L−1 mixture of sunset yellow FCF and tartrazine at the MWCNTs/GCE and poly(4-ABA)/MWCNTs/GCE in phosphate buffer pH 7.0. Modulation amplitude is 50 mV, modulation time is 50 ms, potential scan rate is 20 mV s−1.
Figure 9
Figure 9
Effect of phosphate buffer pH on the voltammetric characteristics of 100 µmol L−1 of sunset yellow FCF and tartrazine at the poly(4-ABA)/MWCNTs/GCE: (a) the changes of oxidation potentials; (b) the changes of oxidation currents.
Figure 10
Figure 10
Cyclic voltammograms of azo dyes at the poly(4-ABA)/MWCNTs/GCE in phosphate buffer pH 4.8 at various potential scan rates: (a) 100 µmol L−1 of sunset yellow FCF; (b) 500 µmol L−1 of tartrazine.
Scheme 2
Scheme 2
Electrooxidation of sunset yellow FCF and tartrazine.
Figure 11
Figure 11
Baseline-corrected differential pulse voltammograms of sunset yellow FCF and tartrazine equimolar mixtures at the poly(4-ABA)/MWCNTs/GCE in phosphate buffer pH 4.8: (a) 0.010–0.75 µmol L−1; (b) 0.75–5.0 µmol L−1. Modulation amplitude is 100 mV, modulation time is 25 ms, potential scan rate is 20 mV s−1.
Figure 12
Figure 12
Baseline-corrected differential pulse voltammograms of sunset yellow FCF and tartrazine non-equimolar mixtures at the poly(4-ABA)/MWCNTs/GCE in phosphate buffer pH 4.8: (a) fixed 1.0 µmol L−1 concentration of tartrazine and varied concentration of sunset yellow FCF; (b) fixed 1.0 µmol L−1 concentration of sunset yellow FCF and varied concentration of tartrazine. Modulation amplitude is 100 mV, modulation time is 25 ms, potential scan rate is 20 mV s−1.
Figure 13
Figure 13
Baseline-corrected differential pulse volammograms of 0.05 µmol L−1 mixture of sunset yellow FCF and tartrazine in the absence and in the presence of 50 µmol L−1 ascorbic acid at the MWCNTs/GCE and poly(4-ABA)/MWCNTs/GCE in phosphate buffer pH 4.8. Modulation amplitude is 100 mV, modulation time is 25 ms, potential scan rate is 20 mV s−1.
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