Search Results (31)

Synthetic dyes of various classes are widely applied in food production. Reliable and simple methods of dye determination are in demand for food quality control. Novel, sensitive, and selective voltammetric sensors based on glassy carbon electrodes modified with mixtures of metal oxide nanoparticles (NPs) dispersed in water or surfactant media have been developed for the first time for Sunset Yellow FCF, Brilliant Blue FCF, and Quinoline Yellow. Mixtures of CeO₂ and SnO₂ NPs dispersed in surfactants or CeO₂ and Fe₂O₃ NPs are the best sensing layers for the determining of Sunset Yellow FCF and Quinoline Yellow or Brilliant Blue FCF. Full article

This study focused on searching for more effective nanomaterials for environmental remediation and health protection; thus, coliform bacteria, yeast and the organic food dye sunset yellow were selected as target pollutants to be eliminated under solar light by Ag/Cr-TiO₂ and Pd/Cr-TiO₂. Firstly, Cr³⁺ was in situ incorporated into the anatase crystalline lattice by the sol-gel method; then, Ag or Pd nanoparticles were deposited on Cr-TiO₂ by chemical photoreduction. The scientific challenge addressed by the development of these composites was to analyse the recovery of Cr, to be employed in photocatalyst formulation and the enhancement of the TiO₂ photocatalytic activity by addition of other noble metals. By extensive characterization, it was found that after TiO₂ doping with chromium, the parameters of the crystal lattice slightly increased, due to the incorporation of Cr ions into the lattice. The TiO₂ band gap decreased after Cr addition, but an increase in the optical absorptions towards the visible region after noble metals deposition was also observed, which was dependent of the Ag or Pd loading. Generally, it was observed that the noble metals type is a factor that strongly influenced the effectiveness of the photocatalysts concerning each substrate studied. Thus, by using Ag(0.1%)/Cr-TiO₂, the complete elimination of E. coli from samples of water coming from a highly polluted river was achieved. Pd(0.5%)/Cr-TiO₂ showed the highest efficiency in the elimination of S. cerevisiae from a lab prepared strain. On the other hand, the Pd(0.1%)/Cr-TiO₂ sample shows the highest dye degradation rate, achieving 92% of TOC removal after 180 min. Full article

Drying–wetting cycles play a crucial role in the investigation of the origin of life as processes that both concentrate and induce the supramolecular assembly and polymerization of biomolecular building blocks, such as nucleotides and amino acids. Here, we test different microfluidic devices to study the dehydration–hydration cycles of the aqueous solutions of small molecules, and to observe, by optical microscopy, the insurgence of phase transitions driven by self-assembly, exploiting water pervaporation through polydimethylsiloxane (PDMS). As a testbed, we investigate solutions of the chromonic dye Sunset Yellow (SSY), which self-assembles into face-to-face columnar aggregates and produces nematic and columnar liquid crystal (LC) phases as a function of concentration. We show that the LC temperature–concentration phase diagram of SSY can be obtained with a fair agreement with previous reports, that droplet hydration–dehydration can be reversibly controlled and automated, and that the simultaneous incubation of samples with different final water contents, corresponding to different phases, can be implemented. These methods can be further extended to study the assembly of diverse prebiotically relevant small molecules and to characterize their phase transitions. Full article

Sunset Yellow FCF (SY FCF) is one of the widely used synthetic azo dyes in the food industry whose content has to be controlled for safety reasons. Electrochemical sensors are a promising tool for this type of task. A voltammetric sensor based on a combination of tin and cerium dioxide nanoparticles (SnO₂–CeO₂ NPs) with surfactants has been developed for SY FCF determination. The synergetic effect of both types of NPs has been confirmed. Surfactants of various natures (sodium lauryl sulfate (SLS), Brij^® 35, and hexadecylpyridinium bromide (HDPB)) have been tested as dispersive media. The best effects, i.e., the highest oxidation currents of SY FCF, have been observed in the case of HDPB. The sensor demonstrates a 4.5-fold-higher electroactive surface area and a 38-fold-higher electron transfer rate compared to the bare glassy carbon electrode (GCE). The electrooxidation of SY FCF is an irreversible, two-electron, diffusion-driven process involving proton transfer. In differential pulse mode in Britton–Robinson buffer (BRB) pH 2.0, the sensor gives a linear response to SY FCF from 0.010 to 1.0 μM and from 1.0 to 100 μM with an 8.0 nM detection limit. The absence of an interferent effect from other typical food components and colorants has been shown. The sensor has been tested on soft drinks and validated with the standard chromatographic method. Full article

Dye wastewater containing bisphenol A (BPA) and dyes as pollutants has not been adequately studied. Our previous study revealed that thermoplastic polyurethane (TPU) nanofiber membranes (NFMs) modified by the addition of polyethyleneimine (PEI) and polydopamine (PDA) satisfactorily adsorb dyes. Herein, we first optimized the synthesis conditions for such membranes, noting a PEI/PDA monomer ratio of 2:2 and a deposition time of 48 h to be optimal. Experiments using these membranes revealed that binary systems containing BPA and the dyes (Congo red (CR), Eosin yellow (EY), or sunset yellow (SY)) exhibit three adsorption behaviors. CR and BPA compete with each other for adsorption sites, decreasing the maximum adsorption capacity (Q_max) for CR 208.3 mg/g (in a monomeric system) to 182.4 mg/g. The adsorption rates for CR and BPA decreased from 0.002 min⁻¹ and 0.331 min⁻¹ in the monomeric systems to 8.37 × 10⁻⁴ min⁻¹ and 0.072 min⁻¹, respectively, in the binary CR–BPA system, exhibiting antagonistic effects. When EY and BPA coexisted, Q_max for EY increased from 60.0 (monomeric) to 71.9 mg/g, whereas that for BPA increased from 35.6 to 43.2 mg/g, showing a synergistic effect due to the possible bridging effect. The adsorption sites for SY and BPA are independent of each other. The novelty of this study is the finding that PDA/PEI-TPU NFMS exhibited high adsorption capacity for dyes and BPA in binary composite systems and PDA/PEI-TPU NFMs showed different adsorption patterns for three dye–BPA binary composite systems. The preparation of PDA/PEI-TPU NFMs and the investigation of the adsorption mechanism for dye–BPA binary composite systems are not only of theoretical importance but also provide experimental and data support for practical applications. Full article

Presently, water pollution poses a serious threat to the environment; the removal of organic pollutants from resources, especially dyes, is very important. Nanofiltration (NF) is a promising membrane method to carry out this task. In the present work, advanced supported poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) membranes were developed for NF of anionic dyes using bulk (the introduction of graphene oxide (GO) into the polymer matrix) and surface (the deposition of polyelectrolyte (PEL) layers by layer-by-layer (LbL) technique) modifications. The effect of PEL combinations (polydiallyldimethylammonium chloride/polyacrylic acid (PAA), polyethyleneimine (PEI)/PAA, and polyallylamine hydrochloride/PAA) and the number of PEL bilayers deposited by LbL method on properties of PPO-based membranes were studied by scanning electron microscopy (SEM), atomic force microscopy (AFM), and contact angle measurements. Membranes were evaluated in NF of food dye solutions in ethanol (Sunset yellow (SY), Congo red (CR), and Alphazurine (AZ)). The supported PPO membrane, modified with 0.7 wt.% GO and three PEI/PAA bilayers, exhibited optimal transport characteristics: ethanol, SY, CR, and AZ solutions permeability of 0.58, 0.57, 0.50, and 0.44 kg/(m²h atm), respectively, with a high level of rejection coefficients—58% for SY, 63% for CR, and 58% for AZ. It was shown that the combined use of bulk and surface modifications significantly improved the characteristics of the PPO membrane in NF of dyes. Full article

Magnetic molecularly imprinted polymers (MMIPs) contain the predesigned specialized recognition capability that can be chosen to build credible functional materials, that are easy to handle and have a good degree of specificity. Hence, the given piece of work is intended to design a novel electrochemical sensor incorporating magnetite-based molecularly imprinted polymers. The building materials consisted of a cross-linker (EGDMA), reaction-initiator (AIBN), monomer (methylene succinic acid-MSA), and template molecule (Sunset Yellow-SY dye). MMIPs exhibited a diameter of 57 nm with an irregular shape due to the presence of cavities based on SEM analysis. XRD patterns exhibited crystallinity, as well as amorphous peaks that are attributed to polymeric and non-polymeric frameworks of MMIPs. The crystallite size of the MMIPs from XRD analysis was found to be 16.28 nm based on the Debye-Scherrer’s equation. Meanwhile, the FTIR bands showed the synthesis of MMIPs using monomer and methylene succinic acid. The sorption data at the optimized operating conditions (pH 2, sorbent dosage 3 mg, time 18 min) showed the highest sorption capacity of 40 mg/g. The obtained data best fitted to the Langmuir sorption isotherm and followed the pseudo-second-order kinetics. The magneto-sensors were applied for ultrasensitive, rapid, and simple sensing of SY dye. The electrochemical experiments were run at the operating condition range of (scan rate 10–50 mV/s, tads 0–120 s, pH 5–9, potential range 1–1.5 V for CV and 1–1.3 V for SWAdASV). The linear range of detection was set to 1.51 × 10⁻⁶ M to 1.51 × 10⁻⁶ M posing LOD and LOQ values of 8.6242 × 10⁻⁵ M and 0.0002874 M, respectively. The regression analysis value for the calibration was found to be 0.950. Additionally, high adsorption efficiency, selectivity, reusability, and strong structural stability of the magneto-sensors showed potential use for SY detection in real samples. These characteristics make MMIPs a viable electrochemical substrate for the detection of chemical contaminants in the environment and in health-related products. Full article

In this study, aqueous two-phase systems (ATPSs) containing a cationic and anionic surfactants mixture were used for the preconcentration of the synthetic food dyes Allura Red AC, Azorubine, Sunset Yellow, Tartrazine, and Fast Green FCF. A rapid, simple, low cost, affordable, and environmentally friendly methodology based on microextraction in ATPSs, followed by spectrophotometric/colorimetric determination of the dyes, is proposed. The ATPSs are formed in mixtures of benzethonium chloride (BztCl) and sodium N-lauroylsarcosinate (NaLS) or sodium dihexylsulfosuccinate (NaDHSS) under the molar ratio close to equimolar at the total surfactant concentration of 0.01–0.20 M. The density, viscosity, polarity, and water content in the surfactant-rich phases at an equimolar ratio BztCl:NaA were determined. The effects of pH, total surfactant concentration, dye concentration, and time of extraction/centrifugation were investigated, and the optimum conditions for the quantitative extraction of dyes were established. The smartphone-based colorimetric determination was employed directly in the extract without separating the aqueous phase. The analytical performance (calibration linearity, precision, limits of detection and quantification, reproducibility, and preconcentration factor) and comparison of the spectrophotometric and smartphone-based colorimetric determination of dyes were evaluated. The method was applied to the determination of dyes in food samples and food-processing industrial wastewater. Full article

In this work, a metal–organic framework (MOF), copper benzene dicarboxylate (Cu-MOF), was tested for the adsorptive recovery of organic dyes (Sunset Yellow FCF, Tartrazine, Orange II, and Methyl Orange) from aqueous solutions. Studies were also carried out to determine the effects of various parameters, and isothermal and kinetic models were proposed. The adsorption capacity of Cu-MOF was much higher than that of activated carbon. The experimental data are best described by the Langmuir isotherm model (R² > 0.997) and show the ability of Cu-MOF to adsorb 435 mg/g of the dye under optimal conditions. The study of the kinetics of the dye adsorption process followed a pseudo-second-order kinetic model indicating the coexistence of physical and chemisorption, with diffusion within the particles being the rate-limiting step. Thermodynamic studies were also carried out, and they led to the conclusion that the adsorption of the dye was a feasible, spontaneous, and exothermic process (−25.53 kJ mol⁻¹). The high organic dye recovery shows that Cu-MOF can be used as an efficient and reusable adsorbent for the extraction of dyes from aqueous solutions. These studies may lead to economic interest in this adsorbent material for environmental purposes. Full article

Due to the recent increase in average living standards, food safety has caught public attention. It is necessary to conduct a qualitative and quantitative rapid test of prohibited food additives since the inclusion of food additives or the improper usage of synthetic dyes can negatively impact on the human health. Herein, a highly sensitive method for Sunset Yellow detection based on a glassy carbon electrode modified with few-layer graphenes was proposed. The electrochemical behavior of SY at the GR-exf/GCE modified surface was investigated by Cyclic Voltammetry, Square Wave Voltammetry, Electrochemical Impedance Spectroscopy and Amperometry. The influences of pH, scan rate, and interfering species were studied. Under optimized conditions, the developed sensor shows good linearity over a broad SY concentration range, e.g., 0.028–30 µM, with a low limit of detection (LOD = 0.0085 µM) and quantification (LOQ = 0.028 µM) (data obtained by amperometric technique). Furthermore, the modified electrode shows good selectivity, precision and sensitivity and has been successfully applied for SY quantification from commercially available pharmaceutical formulation as well as from candy bars and orange juice. Full article

Tartrazine and brilliant blue FCF are synthetic dyes used in the food, cosmetic and pharmaceutical industries. The individual and/or simultaneous control of their concentrations is required due to dose-dependent negative health effects. Therefore, the paper presents experimental results related to the development of a sensing platform for the electrochemical detection of tartrazine and brilliant blue FCF based on a glassy carbon electrode (GCE) modified with MnO₂ nanorods, using anodic differential pulse voltammetry. Homogeneous and stable suspensions of MnO₂ nanorods have been obtained involving cetylpyridinium bromide solution as a cationic surfactant. The MnO₂ nanorods-modified electrode showed a 7.9-fold increase in the electroactive surface area and a 72-fold decrease in the electron transfer resistance. The developed sensor allowed the simultaneous quantification of dyes for two linear domains: in the ranges of 0.10–2.5 and 2.5–15 μM for tartrazine and 0.25–2.5 and 2.5–15 μM for brilliant blue FCF with detection limits of 43 and 41 nM, respectively. High selectivity of the sensor response in the presence of typical interference agents (inorganic ions, saccharides, ascorbic and sorbic acids), other food dyes (riboflavin, indigo carmine, and sunset yellow), and vanillin has been achieved. The sensor has been tested by analyzing soft and isotonic sports drinks and the determined concentrations were close to those obtained involving the chromatography technique. Full article

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. Full article

Synthetic colorants, in particular tartrazine and brilliant blue FCF, are widely used in food chemistry and technology although they can give negative health effects of various severities. Therefore, sensitive, selective, simple, and reliable methods for the quantification of these dyes are required. A glassy carbon electrode (GCE) modified with manganese dioxide nanorods (MnO₂ NR) dispersed in cetylpyridinium bromide gives a sensitive response to tartrazine and brilliant blue FCF in mixtures. Electrode modification provides a 7.9-fold increase in the electroactive surface area and a 72-fold decrease in electron transfer resistance. Simultaneous voltammetric quantification of colorants was performed in phosphate buffer pH 7.0 in differential pulse mode. The linear dynamic ranges of 0.10–2.5 and 2.5–15 µM of tartrazine and 0.25–2.5 and 2.5–15 µM of brilliant blue FCF were obtained with the limits of detection of 43 and 41 nM, respectively. The advantage of the sensor developed is the high selectivity of response in the presence of typical interferences (inorganic ions, saccharides, ascorbic and sorbic acids) and other food colorants (riboflavin, indigo carmine, and sunset yellow). The practical applicability of the approach is shown in soft and isotonic sports drinks and is validated by comparison to chromatography. Full article

Considering the notable mechanical properties of thermoplastic polyurethane (TPU), polydopamine–polyethyleneimine (PEI) -modified TPU nanofiber membranes (PDA/PEI-TPU NFMs) have been developed successfully for removal of anionic azo dyes. The adsorption capacity of PDA/PEI-TPU NFMs was evaluated using three anionic dyes: congo red (CR), sunset yellow (SY), and methyl orange (MO). Interestingly, it exhibited different adsorption behaviors and mechanisms of CR on PDA/PEI-TPU NFMs compared with SY and MO. With the decrease in pH, leading to more positive charges on the PDA/PEI-TPU NFMs, the adsorption capacity of SY and MO increased, indicating electrostatic interaction as a main mechanism for SY and MO adsorption. However, wide pH range adaptability and superior adsorption have been observed during the CR adsorption process compared to SY and MO, suggesting a synergistic effect of hydrogen bonding and electrostatic interaction, likely as a critical factor. The adsorption kinetics revealed that chemical interactions predominate in the CR adsorption process, and multiple stages control the adsorption process at the same time. According to the Langmuir model, the maximum adsorption capacity of CR, SY and MO were reached 263, 17 and 23 mg/g, respectively. After six iterations of adsorption–desorption, the adsorption performance of the PDA/PEI-TPU NFMs did not decrease significantly, which indicated that the PDA/PEI-TPU NFMs have a potential application for the removal of CR molecules by adsorption from wastewater. Full article

The substitution of artificial colorants for pigments extracted from fruits is a highly desirable strategy in the food industry for the manufacture of natural, functional, and safe products. In this work, a 100% natural spray-dried (SD) microencapsulated colorant of pink guava pulp, using aloe vera (AV) or Opuntia ficus-indica (OFI) mucilage as functional encapsulating material, was prepared and evaluated as an additive into a yogurt (Y) matrix. The characterization of yogurt samples supplemented with OFI (Y-SD-OFI) and AV (Y-SD-AV) mucilage-covered guava pulp microcapsules was carried out through carotenoid quantification using UV–vis and HPLC–MS techniques, dietary fiber content, antioxidant capacity, colorimetry, and textural analysis, as well as by an evaluation of color stability after 25 days of storage at 4 °C in the dark. These physicochemical characteristics and color stability on the Y-SD-OFI and Y-SD-AV samples were compared with those of a commercial yogurt (control sample, Y-C) containing sunset yellow FCF synthetic colorant (E110). Y-SD-OFI and Y-SD-AV samples exhibited a high content of lycopene, dietary fiber, and antioxidant activity, which were absent in the control sample. Microencapsulated lycopene imparted a highly stable color to yogurt, contrary to the effect provided by the E110 dye in the control sample. The texture profile analysis revealed an increase in firmness, consistency, and cohesion in the Y-SD-OFI sample, contrary to the Y-SD-AV and Y-C samples, which was attributed to the variation in fiber concentration in the microcapsules. The incorporation of OFI and AV mucilage microparticles containing pink guava pulp into yogurt demonstrated its potential application as a functional natural colorant for dairy products. Full article