Determination of eight synthetic food colorants in drinks by high-performance ion chromatography

Fluorescent composite based on peptide nanotubes activating coumarin 6 for sensitive detection of new coccine in food samples

New coccine (NC), as a kind of common colorant, has been frequently used in our daily life. Herein, the fluorescent composite (PNTs@C6) prepared by the hydrophobic non-covalent interaction between peptide nanotubes and coumarin 6 (C6) was designed for the determination of NC. Due to the activation of C6 by peptide nanotubes, the composite exhibits strong green fluorescence emission, which can be selectively quenched by NC through the inner filter effect. Therefore, a new fluorescent method based on the PNTs@C6 composite for NC detection was constructed. Under optimal conditions, the fluorescence quenching of the sensor exhibits a good linear relationship with the concentration of NC in the range of 0.01-10 μM and the limit of detection is 3.6 nM. Furthermore, the strategy shows simplicity, rapid response and high selectivity and has been successfully applied to the detection of NC in food samples.

A novel voltammetric amaranth sensor based on screen printed electrode modified with polypyrrole nanotubes

Azo dyes are the most used type of dye in the textile industry. Some of these dyes have the potential to be extremely toxic to both human health and the environment. The purpose of this study was to develope an electrochemical sensor for detection of amaranth. The electrochemical sensor based on the modification of a screen-printed electrode via polypyrrole nanotubes (PPy NTs/SPE) for detection of amaranth was developed. The preparation of PPy NTs was performed through the pyrrole monomer oxidation with iron (III) chloride in exposure to methyl orange as structure-guiding agent. Findings exhibited an excellent electrocatalytic activity of as-fabricated sensor for amaranth detection. Our sensor under the optimized circumstances also had a broad linear dynamic range (between 0.03 μM and 290.0 μM) and a narrow limit of detection (0.01 μM) towards the amaranth detection. Moreover, the proposed sensor could practically and successfully determine the amaranth content present in the real food specimens, with acceptable recovery rates.

A label-free fluorescence nanosensor based on nitrogen and phosphorus co-doped carbon quantum dots for ultra-sensitive detection of new coccine in food samples

In this paper, an innovative method for the sensitive detection of new coccine using N, P-doped carbon quantum dots (N,P-CQDs) as fluorescent nanosensor is reported for the first time. The sensing mechanism is based on the fluorescence quenching of N,P-CQDs by new coccine through inner filter effect (IFE). N,P-CQDs were prepared by simple hydrothermal treatment of citric acid, phosphoric acid and ethylenediamine. Under the optimal conditions, the new coccine has two good linear responses in the concentration range of 0.2-100 and 100-200 μM, and the detection limits are as low as 24.8 and 9.4 nM, respectively. Our developed nanosensor has been successfully used for the determination of new coccine in food samples with good precision and high accuracy. This work highlights the economic, rapid, simple, selective and ultra-sensitive for new coccine detection, and opens up a new way for the monitoring of new coccine in actual food samples.

Quantification of permitted synthetic colours in food by liquid chromatographic methods: a review on analytical methods and their performance

Colours, natural and synthetic, are substances which add or restore colour to a food after processing or storage. They are widely used by food manufacturers but may pose a potential risk to human health. Most food safety authorities set up regulations to limit the use of synthetic colours, and monitor their levels and consumption by the general public. Therefore, validated analytical methods are needed to fulfil this requirement. This review presents a comprehensive overview of various liquid chromatographic methods used for quantification of permitted synthetic colours in foods. Available analytical methods have been assessed for their fitness for purpose in terms of extraction, clean-up, liquid chromatographic separation, quantification and method performance. The advantages and disadvantages are given of available analytical methods for analysing 24 synthetic colours, permitted for use by different jurisdictions. Gaps in the knowledge and levels of validation are identified and recommendations made on further research to develop suitable methods for routine monitoring of these permitted synthetic colours.

Plasmonic nanoparticles on metal-organic framework: A versatile SERS platform for adsorptive detection of new coccine and orange II dyes in food

Synthetic dyes have been widely applied to food processing, but abuse of colourants in food may pose risks to human health. To analyze new coccine (NC) and orange II (OII) in food, a versatile surface-enhanced Raman scattering (SERS) platform was proposed. A metal-organic framework (MOF, UiO-66(NH₂)) with octahedral crystal structure was synthesized and gold nanoparticles were grown on the MOF surface to fabricate UiO-66(NH₂)@Au versatile SERS platform. The UiO-66(NH₂)@Au displayed much better SERS performance than gold nanoparticles with high R² of 0.9684 for NC and 0.9912 for OII and low LOD of 0.4015 mg/L for NC and 0.0546 mg/L for OII. The recoveries of NC and OII in Mirinda soft drink and paprika ranged from 82.92 to 109.63%. This study provided a sensitive and rapid method for determination of NC and OII through UiO-66(NH₂)@Au, and the proposed SERS platform revealed great potential for analyzing synthetic colourants in food samples.

Synthetic Food Dyes – Some Aspects Of Use And Methods Of Determination

Color is one of the key ingredients for increasing the appetizing of food, so food dyes have become firmly established in food production technologies. However, with the acquisition of toxicity data of synthetic food dyes (SFD), there were restrictions and standards for their content in food have emerged. Numerous papers published in recent years demonstrate the importance of the problem of the use and definition of SFD. The review contains over 180 literary references in the field of usage and methods of determination of synthetic food dyes, among them regulatory documents (regulations), official internet resources of international and Ukrainian organizations, review articles and original works. Varieties of chromatography, enzyme-linked immunoassay, optical and electrochemical methods are used to identify and determine SFD. Special attention was paid to voltammetry (VA) as a method that is cheaper than chromatography and completely satisfies selectivity, sensitivity, reliability requirements and is compatible with the concept of green analytical chemistry, as it doesn't need organic solvents. Moreover, single sweep voltammetry can be considered as a screening method with low limits of determination and rapid respons

Sensitive and Selective Detection of New Red Colorant Based on Surface-Enhanced Raman Spectroscopy Using Molecularly Imprinted Hydrogels

A polyacrylamide-based molecularly imprinted hydrogel (MIH) doped with positively charged gold nanoparticles (Au NPs) has been synthesized via a free radical polymerization of acrylamide (AM) aqueous solution containing positively charged Au NPs as a Raman active substrate, New Red colorant as a template molecule, N,N’-methylenebis(acrylamide) as a crosslinking agent, and potassium persulfate as an initiator. The Au NPs-doped MIHs were subsequently explored as a Raman active substrate for the sensitive and selective detection of New Red colorant via surface-enhanced Raman spectroscopy (SERS). The logarithmic intensity of the characteristic peak of New Red at 1572 cm−1 was proportional to the logarithmic concentration of New Red with a detection linear range of 1.64 × 10−6 to 1.64 × 10−4 M and a limit of detection (LOD) of 1.64 × 10−7 M. The recoveries ranged from 86.3% to 100.6% with a relative standard deviation (RSD) in the range of 2.3% to 7.7%. The RSD and recovery rates for the detection of New Red spiked in a sports drink sample were 1.8% to 7.7% and 91.0% to 97.1%, respectively. These results showed that SERS combined with MIHs as Raman active substrates could provide a sensitive, selective, and effective approach for the detection of the New Red colorant in beverage matrix.

Identification and Quantitation of Water-Soluble Synthetic Colors in Foods by Liquid Chromatography/Ultraviolet-Visible Method Development and Validation

A simple and sensitive liquid chromatography method of analysis has been developed and validated for the simultaneous quantitative determination of food colors in a broad range of foods. The method of analysis applies specific extraction solutions to obtain optimal color extraction. The extraction solutions are composed of different proportions of methanol and ammonium acetate, as the ion-pairing agent. Analysis was performed on reverse-phase C18 Poroshell column with ammonium acetate, methanol, acetonitrile, and acetone gradient elution as the mobile phases. Multiple-specific wavelengths were used to monitor color additives in the visible range to provide higher sensitivity and expanded scope needed for a large number of analytes. All 27 color compounds showed good linearity with regression coefficients predominantly above 0.990. The limit of detection and limit of quantitation values ranged from 0.10 to 0.43 and from 0.34 to 1.45 μg/g, respectively. The precision of the method ranged from 1.4 to 15.9%, while recoveries averaged 72% across all food commodities tested. The method of analysis offers convenience and adequate sensitivity for the analysis of a wide variety of food matrices containing a broad range of colors.

Research on the Determination of 10 Industrial Dyes in Foodstuffs

An efficient method was developed for the simultaneous determination of 10 industrial dyes (basic orange 2, basic orange 21, basic orange 22, acid orange II, auramine, basic rhodamine B and Sudan I-IV) in the foodstuffs using high-performance liquid chromatography coupled with diode array detector. Samples were extracted with acetonitrile and cleaned up on a solid phase extraction cartridge using HLB. The chromatographic separation was achieved on a C18 column using a mobile phase consisting of methanol and 10 mmol/L ammonium acetate with 0.1% formic acid by gradient elution. Good linearity (r ≥ 0.9993) was observed between 0.050 and 5.0 μg/mL. The limits of detection were in the range of 0.007-0.01 mg/kg, high recoveries (80.6-104%) and good reproducibility (1.1-5.7%) were obtained. Such method is simple, feasible and accurate, which can be applied to the quantification of 10 dyes in food samples.

Green effervescence assisted dispersive liquid–liquid microextraction based on a hydrophobic deep eutectic solvent for determination of Sunset Yellow and Brilliant Blue FCF in food samples

In this study, a simple, fast and sensitive method called effervescence assisted dispersive liquid–liquid microextraction based on a hydrophobic deep eutectic solvent (EADLLME-DES) was used to extract synthetic dyes from food samples.

Organic Colouring Agents in the Pharmaceutical Industry

Food dyes are largely used in the process of manufacturing pharmaceutical products. The aim of such a procedure is not only to increase the attractiveness of products, but also to help patients distinguish between pharmaceuticals. Various dyes, especially organic colouring agents, may in some cases have a negative impact on the human body. They are incorporated into pharmaceutical products including tablets, hard gelatine capsules or soft gelatine capsules, lozenges, syrups, etc. This article provides an overview of the most widely used colouring agents in pharmaceuticals, their characteristics and the EU legislation which regulates their use.

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.

Floral parts of Gomphrena globosa L. as a novel alternative source of betacyanins: Optimization of the extraction using response surface methodology

The present study describes a novel mechanical process for the pigmented parts of Gomphrena globosa L. The effects of the variables of the maceration extraction of betacyanins have not been properly described. Therefore, this study also aims to optimize the conditions that maximize betacyanins extraction from G. globosa as an alternative source. Assisted by response surface methodology, an experimental design was developed for testing the extraction variables (time, temperature, ethanol-water proportion and solid-liquid ratio). The responses used were betacyanins quantification (by HPLC-PDA-MS/ESI and spectrophotometric analysis), the extraction-yield and the colour intensity of the produced powder. The betacyanins identified were gomphrenin and isogomphrenin II and III. The highest betacyanins content (∼45mg/g) was obtained by 165min, 25°C, 0% of ethanol and 5g/L of solid-liquid ratio. The betacyanins content from the floral parts of G. globosa is higher than those normally found in other sources highlighting its industrial application.

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.

Quantification of Ponceau 4R in Foods by Indirect Competitive Enzyme-Linked Immunosorbent Assay (icELISA)

As one of the rarely allowable azo dyes, ponceau 4R can be added in some foods in some countries. However, it is necessary to develop a credible and rapid analytical method for its monitoring, because of its potentially harmful risk. The hapten of ponceau 4R was first designed and synthesized by introducing a primary amine group into the structure of ponceau 4R. Based on the well-prepared hapten, the immunogen of ponceau 4R was prepared using glutaraldehyde to link ponceau 4R to the carrier protein. The triggered polyclonal antibody was obtained and tested by ELISA to optimize the proper dilution. An icELISA was developed for ponceau 4R, and the IC50 of the method is 36.82 ng/mL. The limit of detection is 0.80 ng/mL, and the linear range is 1-10000 ng/mL. Five selected structural analogues have no cross-reactivity with the anti-ponceau 4R polyclonal antibody (<0.3). In three food samples (grape juice, carbonated beverage, and RIO cocktail), the assay exhibits good stability and reproducibility with a recovery range of 93.87-103.77%, and the intra- and interassay coefficients of variation were <11.73%. The results indicate that the proposed icELISA is sensitive, accurate, specific, and simple, which provides an alternative for the detection of ponceau 4R in foods.

Identification and determination of 34 water-soluble synthetic dyes in foodstuff by high performance liquid chromatography-diode array detection-ion trap time-of-flight tandem mass spectrometry

An accurate method combining high performance liquid chromatography (HPLC) with diode array detection (DAD) and ion-trap time-of-flight mass spectrometry (IT-TOF/MS) was developed for simultaneous identification and quantification of 34 water-soluble synthetic dyes in foodstuff. Fragmentation patterns of synthetic dyes were proposed based on IT-TOF/MS. The molecular ion [M+H](+) was not observed in the conventional single-stage mass spectra for most of synthetic dyes. The single-stage mass spectra of synthetic dyes all afforded the diagnostic ions [(M-nNa+nH)+H](+) or [(M-nNa+nH)-H](-) in the positive or negative mode. Doubly charged ions were the characteristic ions of azo dyes. An HPLC-DAD method was developed to analyze 34 synthetic dyes in foodstuffs. The limits of detection (LOD) for the dyes were 0.01-0.05 μg/mL. The recoveries were between 76.1% and 105.0% with a RSD ranging from 1.4% to 6.4%. This method was successfully applied to analyzing the 34 water-soluble synthetic dyes in 21 commercial foods.

Quantitative SERS analysis of azorubine (E 122) in sweet drinks

Considering both the potential effects on human health and the need for knowledge of food composition, quantitative detection of synthetic dyes in foodstuffs and beverages is an important issue. For the first time, we report a fast quantitative analysis of the food and drink colorant azorubine (E 122) in different types of beverages using surface-enhanced Raman scattering (SERS) without any sample preparation. Seven commercially available sweet drinks (including two negative controls) with high levels of complexity (sugar/artificial sweetener, ethanol content, etc.) were tested. Highly uniform Au "film over nanospheres" (FON) substrates together with use of Raman signal from silicon support as internal intensity standard enabled us to quantitatively determine the concentration of azorubine in each drink. SERS spectral analysis provided sufficient sensitivity (0.5-500 mg L(-1)) and determined azorubine concentration closely correlated with those obtained by a standard HPLC technique. The analysis was direct without the need for any pretreatment of the drinks or Au surface. Our SERS approach is a simple and rapid (35 min) prescan method, which can be easily implemented for a field application and for preliminary testing of food samples.

Determination of synthetic food colorants in fish products by an HPLC-DAD method

Reliable methods for quantification of synthetic water-soluble colors in complex food matrices are currently not available. The present work describes the development and validation of an improved protocol for the analysis of synthetic food colorants in complex food matrices presenting high protein and/or fat content. The method developed employs an extraction stage, followed by a subsequent sonification, centrifugation and concentration step. A final clean up via SPE on polyamide cartridges was also employed. The isolated colorants were separated and analyzed by an RP-HPLC/DAD system. High and consistent recoveries (min. 81%) and low RSDs (max. 6%) were achieved for all studied colorants. The issue of high fat content matrices was also addressed showing the need for an additional defatting step in the procedure. Overall, the protocol presented shows high precision and accuracy of detection and can provide the basis for future development of similar methods in other complex food matrices.

Advanced analytical methods and sample preparation for ion chromatography techniques

The recently developed advanced ion chromatography techniques and the various sample preparation methods have been summarized in this mini-review.

Determination of seven certified color additives in food products using liquid chromatography

This study describes a new method for determining FD&C Blue No. 1, FD&C Blue No. 2, FD&C Green No. 3, FD&C Red No. 3, FD&C Red No. 40, FD&C Yellow No. 5, and FD&C Yellow No. 6 in food products. These seven color additives are water-soluble dyes that are required to be batch certified by the U.S. Food and Drug Administration (FDA) before they may be used in food and other FDA-regulated products. In the new method, the color additives are extracted from a product using one of two procedures developed for various product types, isolated from the noncolored components, and analyzed by liquid chromatography with photodiode array detection. The method was validated by determining linearity, range, precision, recovery from various matrices, limit of detection, limit of quantitation, and relative standard deviation for each color additive. A survey of 44 food products, including beverages, frozen treats, powder mixes, gelatin products, candies, icings, jellies, spices, dressings, sauces, baked goods, and dairy products, found total color additives ranging from 1.9 to 1221 mg/kg. FDA intends to use the new method for conducting a rigorous, comprehensive dietary exposure assessment of certified color additives in products likely to be consumed by children.

[Simultaneous determination of 14 restricted substances in flavor and fragrant by ultra high performance liquid chromatography]

An ultra high performance liquid chromatographic method was established for the separation and determination of 14 restricted substances in flavor and fragrant samples. The sample was extracted by 10% (v/v) methanol aqueous solution containing 1% (v/v) ammonia. The 14 analytes were separated in 12 min on a Waters BEH C18 column (50 mm x 2.1 mm, 1.7 microm) using acetonitrile and 10 mmol/L ammonium acetate aqueous solution (containing 0.1% (v/v) acetic acid) as mobile phases with gradient elution at a flow rate of 0.2 mL/min and 35 degrees C, and detected by a diode array detector scanned from 200 nm to 500 nm. The regression equations revealed acceptable linearity (correlation coefficients ranged from 0.995 0 to 0.999 9) in the range of 0.10 - 50 mg/L for the 14 analytes. The limits of detection (LODs) were from 0.32 mg/kg to 2.51 mg/kg. The recoveries of the 14 analytes spiked in real samples at 5, 10 and 20 mg/L were 93.0% - 121% with the relative standard deviations (RSDs) of 0.51% - 4.50%. With the advantages of accessibility, high sensitivity and good reproducibility, this simple method can be used in the simultaneous determination of the restricted substances in flavor and fragrant samples.