Determination of synthetic dyes in selected foodstuffs by high performance liquid chromatography with UV-DAD detection

A Sensitive Electrochemiluminescence Sensor for Brilliant Blue FCF Using Ru(bpy)32+ Immobilized Zn-MOF

A novel electrochemiluminescence (ECL) sensor for detection of brilliant blue FCF (BB) has been developed using Ru@Zn-MOF/nafion modified GCE (glass carbon electrode) in this research. Different from conventional method for usage of Ru(bpy)₃²⁺ in solution-phase, Ru(bpy)₃²⁺ here was immobilized on a zinc-metal-organic-framework (Zn-MOF). After adding BB, a significant quenching phenomenon of ECL intensity was observed. The behavior of BB on the quenching effect of Ru(bpy)₃²⁺/Zn-MOF in different conditions was investigated thoroughly and the detection limit was achieved to 2.5 × 10^-8 M in an optimized condition. Furthermore, the interference of some conventional ions and amino acids to the detection of BB was also investigated. Additionally, the composite showed a good effect on the detection of BB in commercial samples. The proposed sensor provided a promising platform for food safety analysis, environmental monitoring and clinical testing.

Highly selective and sensitive detection of amaranth by using carbon dots-based nanosensor

In this work, a novel fluorescence nanosensor for selective and sensitive determination of amaranth was constructed using carbon dots (C-dots). Water soluble C-dots with strong fluorescence were obtained by a simple microwave-assisted method using urea and glycine as raw materials. It was found that amaranth can efficiently and sensitively quench the C-dots fluorescence by the inner filter effect (IFE) and non-radiative energy transfer (NRET) mechanisms. The fluorescence quenching efficiency (F₀/F) was strongly correlated with the concentration of amaranth in the 0.2–30 μM range. The detection limit (LOD) is 0.021 μM. There was no significant change in the fluorescence intensity of C-dots when other potentially interfering substances were present in the system. Our C-dots-based nanosensor was successfully utilized for the analysis of amaranth in drinks and showed rapid, sensitive and accurate responses. It indicates that the novel C-dots-based nanosensor has great potential in amaranth detection for real-life applications.

Illustration of the synthesis of C-dots and the determination of amaranth based on the fluorescence quenching of C-dots.

A novel voltammetric method for the enhanced detection of the food additive tartrazine using an electrochemical sensor

In this paper, a poly (glycine) modified carbon paste electrode (PGMCPE) for sensitive determination of Tartrazine (Tz) was developed. The electrochemical behaviors of Tz at the PGMCPE were investigated by cyclic voltammetry, differential voltammetry and the results showed that the polymer film on electrode exhibited excellent electrocatalytic activity for the electrochemical oxidation of Tz in phosphate buffer solution, pH 7 (PBS). The influencing factors containing a supporting electrolyte, pH of the solution, deposition potential, amount of Tz and scan rate were investigated. The sensor exhibited two linear behavior in the range of 1 × 10⁻⁶ to 2.7 × 10⁻⁵ mol L⁻¹ and 3.5 × 10⁻⁵ to 8.7 × 10⁻⁵ mol L⁻¹ for Tz (correlation coefficients: 0.991 and 0.995 respectively) with detection limit (LOD) of 2.83 × 10⁻⁷ mol L⁻¹, limit of quantification (LOQ) 9.4 × 10⁻⁷ mol L⁻¹ and detection sensitivity (2.0452 μA/μM), for Tz. The results show that the biosensor is sensitive and useful for the determination of Tz.

Determination of Allura Red in the Presence of Cetylpyridinium Bromide by Square-wave Adsorptive Stripping Voltammetry on a Glassy Carbon Electrode

A simple method to determine Allura Red (AR) in cherry gelatin, chili sauce and strawberry juice by square-wave adsorptive stripping voltammetry (SWAdV) in the presence of cetylpyridinium bromide (CPB) is reported. Using a glassy carbon electrode (GCE), Amaranth (AM), Ponceau 4R (P-4R) and AR were oxidized to very close potential values in medium acid pH 3.0 with phosphate buffer solution (PBS), making selective AR detection impossible. Under these conditions AM, P-4R and AR were oxidized at 0.80, 0.77 and 0.81 V, respectively. When small amounts of CPB were added, an AR-CPB aggregate was formed. This change displaced the oxidation almost 0.14 V in the direction of the most positive potential and increased the current almost 50%, while AM and P-4R were oxidized at almost the same potential. Under these conditions, the selective determination of AR in food was possible. Detection limit was 0.032 μmol L^-1. Finally, the method was successfully applied to the determination of AR in these foods.

A New Laccase Based Biosensor for Tartrazine

Laccase enzyme, a commonly used enzyme for the construction of biosensors for phenolic compounds was used for the first time to develop a new biosensor for the determination of the azo-dye tartrazine. The electrochemical biosensor was based on the immobilization of laccase on functionalized methacrylate-acrylate microspheres. The biosensor membrane is a composite of the laccase conjugated microspheres and gold nanoparticles (AuNPs) coated on a carbon-paste screen-printed electrode. The reaction involving tartrazine can be catalyzed by laccase enzyme, where the current change was measured by differential pulse voltammetry (DPV) at 1.1 V. The anodic peak current was linear within the tartrazine concentration range of 0.2 to 14 μM (R² = 0.979) and the detection limit was 0.04 μM. Common food ingredients or additives such as glucose, sucrose, ascorbic acid, phenol and sunset yellow did not interfere with the biosensor response. Furthermore, the biosensor response was stable up to 30 days of storage period at 4 °C. Foods and beverage were used as real samples for the biosensor validation. The biosensor response to tartrazine showed no significant difference with a standard HPLC method for tartrazine analysis.

Food colors: Existing and emerging food safety concerns

Food colors are added to different types of commodities to increase their visual attractiveness or to compensate for natural color variations. The use of these additives is strictly regulated in the European Union, the United States, and many other countries worldwide. There is a growing concern about the safety of some commonly used legal food colorants and there is a trend to replace the synthetic forms with natural products. Additionally, a number of dyes with known or suspected genotoxic or carcinogenic properties have been shown to be added illegally to foods. Robust monitoring programs based on reliable detection methods are required to assure the food is free from harmful colors. The aim of this review is to present an up to date status of the various concerns arising from use of color additives in food. The most important food safety concerns in the field of food colors are lack of uniform regulation concerning legal food colors worldwide, possible link of artificial colors to hyperactive behavior, replacement of synthetic colors with natural ones, and the presence of harmful illegal dyes-both known but also new, emerging ones in food. The legal status of food color additives in the EU, United States, and worldwide is summarized. The reported negative health effects of both legal and illegal colors are presented. The European Rapid Alert System for Food and Feed notifications and US import alerts concerning food colors are analyzed and trends in fraudulent use of color additives identified. The detection methods for synthetic colors are also reviewed.

A Zinc Oxide Nanoflower-Based Electrochemical Sensor for Trace Detection of Sunset Yellow

Zinc oxide nanoflower (ZnONF) was synthesized by a simple process and was used to construct a highly sensitive electrochemical sensor for the detection of sunset yellow (SY). Due to the large surface area and high accumulation efficiency of ZnONF, the ZnONF-modified carbon paste electrode (ZnONF/CPE) showed a strong enhancement effect on the electrochemical oxidation of SY. The electrochemical behaviors of SY were investigated using voltammetry with the ZnONF-based sensor. The optimized parameters included the amount of ZnONF, the accumulation time, and the pH value. Under optimal conditions, the oxidation peak current was linearly proportional to SY concentration in the range of 0.50-10 μg/L and 10-70 μg/L, while the detection limit was 0.10 μg/L (signal-to-noise ratio = 3). The proposed method was used to determine the amount of SY in soft drinks with recoveries of 97.5%-103%, and the results were in good agreement with the results obtained by high-performance liquid chromatography.

Pre-concentration and determination of tartrazine dye from aqueous solutions using modified cellulose nanosponges

In this study, a new absorbent based on cellulose nanosponges modified with methyltrioctylammonium chloride (aliquat 336) was prepared and used for pre-concentration, removal and determination of tartrazine dye, using UV-vis spectrophotometry. This adsorbent was fully characterized using various instrumental techniques such as SEM, FTIR and XRD spectra. The pre-concentration and removal procedures were studied in column and batch modes, respectively. The effects of parameters such as pH of the aqueous medium, methyltrioctylammounium chloride dose, adsorbent amount, desorbing conditions and interfering ions on the adsorption of tartrazine were investigated and optimized. The fitting experimental data with conventional isotherm models revealed that the adsorption followed the Brunauer-Emmett-Teller (BET) model and the maximum adsorption capacity for tartrazine was 180mg/g with modified nanosponges. Under the optimized conditions, the calibration curve was linear over the range of 2-300ng/mL and the limit of detection was 0.15ng/mL. The relative standard deviation (RSD) for 20 and 100ng/mL of tartrazine were 3.1% and 1.5%, respectively. The proposed method was applied for pre-concentration and determination of tartrazine dye in different water samples.

The Determination of Food Dyes in Vitamins by RP-HPLC

Reversed-phase high performance liquid chromatography (RP-HPLC) for the determination of five synthetic food dyes (Quinoline Yellow E104, Sunset Yellow E110, Ponceau 4R E124, Tartrazine E102 and Carmine E120) in vitamins was used. The dyes were analyzed within 10 min using a column with stationary phase C 18 (250 mm × 4.6 mm, 5 μm) at 40 °C with isocratic elution, and the mobile phase contained acetonitrile and a mixture of CH₃COONa:CH₃OH (85:15, v/v) in a ratio of 10:90 (v/v) for yellow-colored capsules and 20:80 (v/v) for red-colored capsules, respectively. A diode-array detector was used to monitor the dyes between 190 and 800 nm. It was established that the analyzed samples contained synthetic dyes in a concentration range from 79.5 ± 0.01 μg/capsule of Ponceau 4R, E124 to 524 ± 0.01 μg/capsule of Tartrazine, E102. The obtained results were compared with existing acceptable daily intakes (ADIs) for individual dyes. This paper provides information about the content of dyes in samples of vitamins. This information is not generally available to consumers.

Fluorescence Turn off Sensor for Brilliant Blue FCF- an Approach Based on Inner Filter Effect

A nanosensor with fluorometric readout based on L-cysteine capped cadmium sulphide quantum dots for discriminative detection and determination of Brilliant blue FCF (BB) (in 0.5 M Tris buffer solution of pH 9.5) over other synthetic food colourants is developed. Mechanism of the nanosensor is based on inner filter effect (IFE). The addition of BB into quantum dot solution might induce the quenching of fluorescence. The nanosensor described in this report reveals its simplicity and flexibility due to less laborious and more cost-effective synthesis. The developed fluorescence sensor showed excellent selectivity towards BB, and allows the detection as low as 3.50 × 10^-7 M. The developed sensor exhibited a linear concentration range of 4.00 × 10^-5 to 4.50 × 10^-6 M. More importantly, the proposed sensor exhibit sensitive responses toward BB in food samples such as sports drink and candies, demonstrating its potential in food analysis, which might be significant in food quality control in the future.

Multifunctional Fe3O4@SiO2-Au Satellite Structured SERS Probe for Charge Selective Detection of Food Dyes

Nanofabrication of multifunctional surface-enhanced Raman scattering (SERS) substrates is strongly desirable but currently remains a challenge. The motivation of this study was to design such a substrate, a versatile core-satellite Fe3O4@SiO2-Au (FA) hetero-nanostructure, and demonstrate its use for charge-selective detection of food dye molecules as an exemplary application. Our experimental results and three-dimensional finite difference time domain (FDTD) simulation suggest that tuning the Au nanoparticle (NP) gap to sub-10 nm, which could be readily accomplished, substantially enhanced the Raman signals. Further layer-by-layer deposition of a charged polyelectrolyte on this magnetic SERS substrate induced active adsorption and selective detection of food dye molecules of opposite charge on the substrates. Molecular dynamics (MD) simulations suggest that the selective SERS enhancement could be attributed to the high affinity and close contact (within a 20 Å range) between the substrate and molecules. Density function theory (DFT) calculations confirm the charge transfer from food dye molecules to Au NPs via the polyelectrolytes. This multifunctional SERS platform provides easy separation and selective detection of charged molecules from complex chemical mixtures.

Simultaneous determination of some common food dyes in commercial products by digital image analysis

A simple and relatively fast image-analysis method using digital images, obtained with a flatbed scanner, has been described. The method was used for the simultaneous determination of four common food dyes, namely, carmoisine, brilliant blue, sunset yellow, and quinoline yellow, in binary mixtures in commercial products without a need for any prior separation steps. The results obtained were validated against a standard high-performance liquid chromatography method and a good agreement was obtained. The parameters affecting the experimental results were optimized. Under the optimal conditions, the method provided acceptable linear ranges (20–250 mg/L) with correlation coefficients higher than 0.998, suitable precision (relative standard deviation ≤ 4.5%), and limits of detection between 4.82 and 8.05 mg/L.

Determination of dyes in cosmetic products by micro-matrix solid phase dispersion and liquid chromatography coupled to tandem mass spectrometry

A simple method based on micro-matrix solid phase dispersion (MSPD) followed by liquid chromatography-mass spectrometry (LC-MS/MS) has been developed for the rapid and simultaneous determination of nine regulated water-soluble dyes in personal care and decorative products. The proposed miniaturized extraction procedure was optimized by means of experimental designs in order to obtain the highest extraction efficiency. Under the optimal selected conditions, the method was validated showing satisfactory performance in terms of linearity, sensitivity, and intra-day and inter-day precision. Recoveries were evaluated in different cosmetic matrices and they can be considered quantitative with average values between 70 and 120% with relative standard deviations (RSD) lower than 15%. Finally, the validated method was applied to 24 samples of cosmetic and personal care products, including decorative makeup, lipsticks, lip gloss, toothpastes, regenerating creams, shampoos, and eye shadows, among others, to cover a broad range of commercial real samples. Seven of the analyzed dyes were detected, being declared all of them in the label list of ingredients. More than 50% of the samples contained at least two dyes. Tartrazine was the most frequently found (50% of the samples) at concentration levels of 0.243-79.9μgg(-1). Other targets were found in 1-9 samples, highlighting the presence of Quinoline at high concentration (>500μgg(-1)) in a toothpaste sample.

Highly-sensitive electrochemical sensing platforms for food colourants based on the property-tuning of porous carbon

It is very challenging to develop highly-sensitive analytical platforms for toxic synthetic colourants that widely added in food samples. Herein, a series of porous carbon (PC) was prepared using CaCO3 nanoparticles (nano-CaCO3) as the hard template and starch as the carbon precursor. Characterizations of scanning electron microscopy and transmission electron microscopy indicated that the morphology and porous structure were controlled by the weight ratio of starch and nano-CaCO3. The electrochemical behaviours of four kinds of widely-used food colourants, Sunset yellow, Tartrazine, Ponceau 4R and Allura red, were studied. On the surface of PC samples, the oxidation signals of colourants enhanced obviously, and more importantly, the signal enhancement abilities of PC were also dependent on the starch/nano-CaCO3 weight ratio. The greatly-increased electron transfer ability and accumulation efficiency were the main reason for the enhanced signals of colourants, as confirmed by electrochemical impedance spectroscopy and chronocoulometry. The prepared PC-2 sample by 1:1 starch/nano-CaCO3 weight ratio was more active for the oxidation of food colourtants, and increased the signals by 89.4-fold, 79.3-fold, 47.3-fold and 50.7-fold for Sunset yellow, Tartrazine, Ponceau 4R and Allura red. As a result, a highly-sensitive electrochemical sensing platform was developed, and the detection limits were 1.4, 3.5, 2.1 and 1.7 μg L(-1) for Sunset yellow, Tartrazine, Ponceau 4R and Allura red. The practical application of this new sensing platform was demonstrated using drink samples, and the detected results consisted with the values that obtained by high-performance liquid chromatography.

TNPs as a novel fluorescent sensor for the selective recognition of fast green FCF: a spectrofluorimetric approach

The fast green FCF dye adsorbed over the surface of the CTAB stabilized tetracene nanoparticles (TNPs) forms a stable, non-fluorescent ground state complex and quenches fluorescence of nanoparticle sensor.

Partial intercalative binding of the food colorant erythrosine to herring sperm DNA

Erythrosine partially inserts into the G–C rich region of hsDNA and induces moderate conformational perturbation of the DNA.

Using dyes for evaluating photocatalytic properties: a critical review

This brief review aims at analyzing the use of dyestuffs for evaluating the photocatalytic properties of novel photocatalysts. It is shown that the use of dyes as predictors for photocatalytic activity has its roots in the pre visible-light activity era, when the aim was to treat effluents streams containing hazardous dyes. The main conclusion of this review is that, in general, dyes are inappropriate as model compounds for the evaluation of photocatalytic activity of novel photocatalysts claimed to operate under visible light. Their main advantage, the ability to use UV-Vis spectroscopy, is severely limited by a variety of factors, most of which are related to the presence of other species. The presence of a second mechanism, sensitization, diminishes the generality required from a model contaminant used for testing a novel photocatalyst. While it is recommended not to use dyes for general testing of novel photocatalysts, it is still understandable that a model system consisting of a dye and a semiconductor can be of large importance if the degradation of a specific dye is the main aim of the research, or, alternatively, if the abilities of a specific dye to induce the degradation of a different type of contaminant are under study.

Determination of sunset yellow and tartrazine in food samples by combining ionic liquid-based aqueous two-phase system with high performance liquid chromatography

We proposed a simple and effective method, by coupling ionic liquid-based aqueous two-phase systems (IL-ATPSs) with high performance liquid chromatography (HPLC), for the analysis of determining tartrazine and sunset yellow in food samples. Under the optimized conditions, IL-ATPSs generated an extraction efficiency of 99% for both analytes, which could then be directly analyzed by HPLC without further treatment. Calibration plots were linear in the range of 0.01-50.0 μg/mL for both Ta and SY. The limits of detection were 5.2 ng/mL for Ta and 6.9 ng/mL for SY. This method proves successful for the separation/analysis of tartrazine and sunset yellow in soft drink sample, candy sample, and instant powder drink and leads to consistent results as obtained from the Chinese national standard method.