A Novel Electrochemical Sensor Based on Poly (Diallyldimethylammonium Chloride)-Dispersed Graphene Supported Palladium Nanoparticles for Simultaneous Determination of Sunset Yellow and Tartrazine in Soft Drinks

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

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.

Specific and Sensitive Detection of Tartrazine on the Electrochemical Interface of a Molecularly Imprinted Polydopamine-Coated PtCo Nanoalloy on Graphene Oxide

A novel electrochemical sensor designed to recognize and detect tartrazine (TZ) was constructed based on a molecularly imprinted polydopamine (MIPDA)-coated nanocomposite of platinum cobalt (PtCo) nanoalloy-functionalized graphene oxide (GO). The nanocomposites were characterized and the TZ electrochemical detection performance of the sensor and various reference electrodes was investigated. Interestingly, the synergistic effect of the strong electrocatalytic activity of the PtCo nanoalloy-decorated GO and the high TZ recognition ability of the imprinted cavities of the MIPDA coating resulted in a large and specific response to TZ. Under the optimized conditions, the sensor displayed linear response ranges of 0.003–0.180 and 0.180–3.950 µM, and its detection limit was 1.1 nM (S/N = 3). The electrochemical sensor displayed high anti-interference ability, good stability, and adequate reproducibility, and was successfully used to detect TZ in spiked food samples. Comparison of important indexes of this sensor with those of previous electrochemical sensors for TZ revealed that this sensor showed improved performance. This surface-imprinted sensor provides an ultrasensitive, highly specific, effective, and low-cost method for TZ determination in foodstuffs.

Highly Sensitive Determination of Tenofovir in Pharmaceutical Formulations and Patients Urine—Comparative Electroanalytical Studies Using Different Sensing Methods

This paper discusses the electrochemical behavior of antiviral drug Tenofovir (TFV) and its possible applicability towards electroanalytical determination with diverse detection strategies using square-wave voltammetry. Namely, oxidation processes were investigated using glassy carbon electrode with graphene oxide surface modification (GO/GCE), while the reduction processes, related to the studied analyte, were analyzed at a renewable silver amalgam electrode (Hg(Ag)FE). Scanning electron microscopy imaging confirmed the successful deposition of GO at the electrode surface. Catalytic properties of graphene oxide were exposed while being compared with those of bare GCE. The resultant modification of GCE with GO enhanced the electroactive surface area by 50% in comparison to the bare one. At both electrodes, i.e., GO/GCE and Hg(Ag)FE, the TFV response was used to examine and optimize the influence of square-wave excitation parameters, i.e., square wave frequency, step potential and amplitude, and supporting electrolyte composition and its pH. Broad selectivity studies were performed with miscellaneous interfering agents influence, including ascorbic acid, selected saccharides and aminoacids, metal ions, non-opioid analgesic metamizole, non-steroidal anti-inflammatory drug omeprazole, and several drugs used along with TFV treatment. The linear concentration range for TFV determination at GO/GCE and Hg(Ag)FE was found to be 0.3–30.0 µmol L^–1 and 0.5–7.0 µmol L^–1, respectively. The lowest LOD was calculated for GO/GCE and was equal to 48.6 nmol L^–1. The developed procedure was used to detect TFV in pharmaceutical formulations and patient urine samples and has referenced utilization in HPLC studies.

Three-dimensional porous reduced graphene oxide decorated with carbon quantum dots and platinum nanoparticles for highly selective determination of azo dye compound tartrazine

In this work, an electrochemical sensor for the azo dye compound tartrazine (TRT) determination was proposed. A screen-printed carbon electrode (SPCE) was modified by depositing three-dimensional porous reduced graphene oxide decorated with carbon quantum dots and platinum nanoparticles (Pt/CQDs@rGO/SPCE). The resulting amount of TRT was observed by differential pulse voltammetry. Under optimal conditions, the sensor exhibited two wide linearities ranging from 0.01 to 1.57 μM and 1.57-9.3 μM with the reliability coefficient of determination of 0.991 and 0.992, respectively. The detection limit (LOD) was also estimated to be 7.93 nM. Moreover, the Pt/CQDs@rGO/SPCE suggested high selectivity in the presence of several interfering agents and azo dye compounds that have a similar structure. Additionally, the Pt/CQDs@rGO/SPCE revealed superior recovery values of about 96.5-101.6% for candy, 99.7-103.5% for soft drinks, 96.0-101.2% for jelly powder, and 98.0-103.0% for water samples. Furthermore, the fabricated sensor exhibits excellent selectivity, stability, reproducibility, and repeatability, indicating a great perspective in the monitoring of TRT. Therefore, it can be speculated that the proposed electrode could be effectively applied to determine TRT in food samples.

Novel Electrochemical Sensors Based on Cuprous Oxide-Electrochemically Reduced Graphene Oxide Nanocomposites Modified Electrode toward Sensitive Detection of Sunset Yellow

Control and detection of sunset yellow is an utmost demanding issue, due to the presence of potential risks for human health if excessively consumed or added. Herein, cuprous oxide-electrochemically reduced graphene nanocomposite modified glassy carbon electrode (Cu₂O-ErGO/GCE) was developed for the determination of sunset yellow. The Cu₂O-ErGO/GCE was fabricated by drop-casting Cu₂O-GO dispersion on the GCE surface following a potentiostatic reduction of graphene oxide (GO). Scanning electron microscope and X-ray powder diffractometer was used to characterize the morphology and microstructure of the modification materials, such as Cu₂O nanoparticles and Cu₂O-ErGO nanocomposites. The electrochemical behavior of sunset yellow on the bare GCE, ErGO/GCE, and Cu₂O-ErGO/GCE were investigated by cyclic voltammetry and second-derivative linear sweep voltammetry, respectively. The analytical parameters (including pH value, sweep rate, and accumulation parameters) were explored systematically. The results show that the anodic peak currents of Cu₂O-ErGO /GCE are 25-fold higher than that of the bare GCE, due to the synergistic enhancement effect between Cu₂O nanoparticles and ErGO sheets. Under the optimum detection conditions, the anodic peak currents are well linear to the concentrations of sunset yellow, ranging from 2.0 × 10⁻⁸ mol/L to 2.0 × 10⁻⁵ mol/L and from 2.0 × 10⁻⁵ mol/L to 1.0 × 10⁻⁴ mol/L with a low limit of detection (S/N = 3, 6.0 × 10⁻⁹ mol/L). Moreover, Cu₂O-ErGO/GCE was successfully used for the determination of sunset yellow in beverages and food with good recovery. This proposed Cu₂O-ErGO/GCE has an attractive prospect applications on the determination of sunset yellow in diverse real samples.

Adsorptive Stripping Voltammetric Determination of Amaranth and Tartrazine in Drinks and Gelatins Using a Screen-Printed Carbon Electrode

A fast, sensitive, and selective method for the simultaneous determination of one pair of synthetic colorants commonly found mixed in food products, Amaranth (AM) and Tartrazine (TZ), based on their adsorption and oxidation on a screen-printed electrode (SPE) is presented. The variation of peak current with pH, supporting electrolyte, adsorption time, and adsorption potential were optimized using square wave adsorptive voltammetry. The optimal conditions were found to be: pH 3.2 (PBS), E_ads 0.00 V, and t_ads 30 s. Under these conditions, the AM and TZ signals were observed at 0.56 and 0.74 V, respectively. A linear response were found over the 0.15 to 1.20 µmol L^-1 and 0.15 to 0.80 µmol L^-1 concentrations, with detection limits (3σ/slope) of 26 and 70 nmol L^-1 for AM and TZ, respectively. Reproducibility for 17.7 µmol L^-1 AM and TZ solutions were 2.5 and 3.0% (n = 7), respectively, using three different electrodes. The method was validated by determining AM and TZ in spiked tap water and unflavored gelatin spiked with AM and TZ. Because a beverage containing both AM and TZ was not found, the method was applied to the determination of AM in a kola soft drink and TZ in an orange jelly and a soft drink powder.