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Para Red (PR) and Sudan dyes have been illegally used as colorants to adulterate certain foods by enhancing their red/orange colour. In addition, they are toxic and carcinogenic. This work presents the development of a simple flow injection chromatographic method combined with chemometric tools to perform the determination of PR, Sudan I (SI) and Sudan II (SII) in food samples. The flow chromatographic system consisted of a low-pressure manifold coupled to a reverse phase monolithic column. A Partial Least Square (PLS) model was applied to resolve overlapped absorption spectra registered for each dye at the corresponding retention time. The relative errors of calibration (RMSECV, %) were 0.49, 0.85 and 0.23, and the relative errors of prediction (RMSEP, %) were 1.12, 0.75 and 0.33 for PR, SI and SII, respectively. The residual predictive deviation (RPD) values obtained were higher than 3.00 for all analytes. The method was successfully applied to quantify the dyes in six different commercial spices samples. The results were compared with the HPLC reference method concluding that there were no significant differences at the studied confidence level (α = 0.05). The proposed method can be used to rapidly determine the analytes in a simple, reliable, low-cost and environmentally-friendly manner. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s13197-021-05299-8.

A simple and sensitive liquid chromatography/tandem mass spectrometry (LC-MS/MS) method for the simultaneous determination of 15 illegal dyes (Sudan I, Sudan II, Sudan III, Sudan IV, Sudan Red G, Sudan Orange G, Sudan Red 7B, Para Red, Dimethyl Yellow, Rahodamine B, Sudan Black B, Sudan Red B, Auramine O, Toluidine Red and Orange II) was developed and validated in sauce, cotton candy, and pickle. The samples were extracted with acetonitrile without the use of solid-phase extraction cartridges. Chromatographic separation was achieved on a Zorbax Eclipse Plus C18 column with a flow rate of 500 µL/min at 45 °C, using a gradient elution with A (10 mM ammonium formate in water with 0.1% formic acid) and B (10 mM ammonium formate in acetonitrile (ACN) with 0.1% formic acid) as the mobile phase. The detection was performed on a AB Sciex 6500 Qtrap mass analyzer under multiple reaction monitoring mode. Limit of detection, quantification, linearity, and precision were determined during the validation process. Recoveries ranged from 82% to 119% for all synthetic dyes, in exception to Orange II in cotton candy and pickle, where signal was suppressed due to high matrix interference and poor ionization. This method offers a simple and rapid approach to detect and quantify prohibited dyes in foodstuff that can be utilized in food contaminant laboratories. Keywords: Food additives, Synthetic dyes, Sauce, Cotton candy, Pickle, LC - MS/MS

A simple approach based on cyclic voltammetry (CV) was developed for the simultaneous determination of dopamine (DA) and uric acid (UA) in the presence of ascorbic acid (AA) using a modified glassy carbon paste electrode (GCPE). In the present study, analytical parameters were optimized and electrochemical performance of modified electrode was investigated. The calibration curves were obtained over the range of 15.97-157.98 μmol L-1 dopamine and 15.97-195.35 μmol L-1 uric acid. Detection limits of 12.38 μmol L-1 dopamine and 3 μmol L-1 uric acid were also obtained at pH 7.0. The modified electrode was used for practical application for the detection of dopamine and uric acid in the real samples of uric acid and dopamine injection, human serum and urine samples.

Introduction Some azo dyes, including Sudans I–IV and Para Red, are genotoxic and may be biotransformed to cancerogenic aromatic amines. They are banned as food and feed additives, but their presence has been detected in food. Aromatic amines are also considered potentially toxic. Online EC–MS is a promising tool to study the transformation mechanisms of xenobiotics such as azo dyes. The aim of the study was to investigate emulation of how azo dyes are enzymatically transformed to amines with EC–MS. Material and Methods The reduction reactions of five azo dyes (Sudans I–IV and Para Red) were conducted using a glassy carbon working electrode and 0.1% formic acid in acetonitrile. Reduction results were compared with the literature and in silico to select preliminary candidates for metabolites. The LC-MS/MS method was used to confirm results obtained by electrochemical reactor. Results A limited number of pre-selected compounds were confirmed as azo dyes metabolites – aniline for Sudan I, aniline and 4-aminoazobenzene for Sudan III, o-toluidine for Sudan IV, and 4-nitroaniline for Para Red. No metabolites were found for Sudan II. Conclusions Electrochemistry–mass spectrometry was successfully applied to azo dyes. This approach may be used to mimic the metabolism of azo dyes, and therefore predict products of biotransformation.

In this study, we present a systematic study of linear and nonlinear optical properties of Para Red with the aim of Z-scan technique and quantum mechanical calculations. The Z-scan experiments were performed using a 532 nm Nd: YAG (SHG) CW laser beam. Para Red exhibited a strong nonlinear refractive index, nonlinear absorption coefficient and third-order nonlinear susceptibility 3.487 × 10−6 cm2/W, 2.341 × 10−1cm/W and 2.157 × 10−4 esu, respectively. Also, quantum chemical analysis was used for the calculation of the dipole moment μ, dipole polarizability α, anisotropy of polarizability Δα and molecular hyperpolarizabilities (β,γ). The results revealed that Para Red has large first and second hyperpolarizabilities. However, from the obtained results, it was found that Para Red can be a promising material for applications in the development of non-linear optical materials.

Magnetic solid-phase extraction is an effective and useful technique to preconcentrate trace analytes from food samples. In this study, a magnetic trimeric chromium octahedral metal-organic framework (Fe3O4-NH2@MIL-101) was fabricated and characterized. Fe3O4-NH2@MIL-101 was applied as an adsorbent of magnetic solid-phase extraction combined with high performance liquid chromatography to effectively isolate and simultaneously determine six Sudan dyes (Para Red, Sudan I–IV, and Sudan Red 7B) from tomato sauce. Potential factors affecting the MSPE were investigated in detail, and adsorption efficiency of Fe3O4-NH2@MIL-101 was compared with those of conventional adsorbents, such as neutral alumina, HLB, and C18. The developed method facilitated the extraction with using only 3 mg of adsorbent in 2 min. In addition, enhancement factors of 50, linear range of 0.01–25 μg/mL, and detection limit (S/N = 3) of 0.5–2.5 μg/kg were obtained. The intra-day and inter-day recoveries for spiked Sudan dyes were in the range of 72.6%–92.9% and 69.6%–91.6%, respectively, with relative standard deviations of ≤9.2%.

Spices are added in order to enhance the organoleptic characteristics of food and culinary dishes, making them more attractive for consumers. The use of illicit cheap colourants might be profitable along the food supply chain, posing undue risks to human health. This work evaluates the feasibility of NIR spectroscopy with chemometrics as a rapid, simple, non-destructive and affordable screening tool to determine the presence of Sudan I, II, III, IV and Para-red dyes in paprika. The dataset comprised unadulterated and adulterated samples with the five studied dyes at different concentration levels. Several multivariate classification models were built with Linear Discriminant Analysis (LDA) and different machine learning techniques. Preliminary results show that a classifier based on only six wavenumbers is able to determine the presence of some of these dyes in food samples in levels that may represent risk to human health. Sensitivities and specificities above 90% were obtained in almost all cases. These results show the feasibility of inexpensive and portable devices that can be useful for screening out adulterated stock along the food chain supply. Fil: Trentanni-hansen, Gimena Jessica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; Argentina Fil: Almonacid, Jonathan Samuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Centro para el Estudio de Sistemas Marinos; Argentina Fil: Albertengo, Liliana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; Argentina Fil: Rodriguez, Maria Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; Argentina Fil: Di Anibal, Carolina Vanesa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; Argentina Fil: Delrieux, Claudio Augusto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca; Argentina. Universidad Nacional del Sur. Departamento de Ingeniería Eléctrica y de Computadoras; Argentina

In this study, a solid-phase extraction-high performance liquid chromatography (SPE-HPLC) method was developed for the determination of Para Red, Orange Ⅱ sodium salt, Sudan Ⅰ, and Sudan Ⅱ in paprika powder based on a self-made porous aromatic framework-6 (PAF-6) solid-phase extraction cartridge. The major factors affecting the extraction efficiency and adsorption capacity of this solid-phase extraction were evaluated. Under optimized conditions, the limits of detection (LODs) and limits of quantification (LOQs) of the four target analytes ranged from 1.5 to 7.0 μg/L and 5.0 to 22.1 μg/L, respectively. The recoveries were in the range of 76.5-89.8%, and the relative standard deviation (RSD) was not more than 5.3% (n=6). Moreover, quantum chemistry calculations were performed to investigate the molecular interaction mechanism between the PAF-6 and target analytes. The results indicated that the target molecules could be stably adsorbed onto the PAF-6. The method is accurate, reliable, and sensitive, and can be successfully applied to detect the four azo dyes in paprika powder.

The mutagenicity of Direct Black 38, Sudan I, and Para Red were evaluated in the in vivo MutaMouse assay and the in vitro MutaMouse primary hepatocyte (PH) assay. Direct Black 38 is an International Agency for Research on Cancer (IARC) Group 1 carcinogen and a prototypical benzidine-based azo compound that requires azo-reduction to yield a DNA-reactive metabolite. Sudan I and Para Red are structurally related azo compounds that have been detected as illegal contaminants in foods. Sudan I is an in vivo mutagen, and both it and Para Red are known to be mutagenic in vitro. Sudan I is oxidized by hepatic and/or bladder enzymes to yield a mutagenic metabolite, but little is known about Para Red. In the present study, Direct Black 38 elicited a significant mutagenic response in the bone marrow, glandular stomach, small intestine and colon in vivo, and in PHs in vitro. Sudan I elicited a weak positive response in the bone marrow and a marginally significant treatment effect in the bladder (p = 0.059); it did not elicit a significant response in PHs in vitro. Para Red elicited a positive response in the colon, as well as in PHs in vitro, albeit at a cytotoxic concentration. The findings are well aligned with the known mechanisms of action of Direct Black 38 and Sudan I; they suggest that intestinal azo-reduction plays an important role in the activation of Para Red. The MutaMouse pH results illustrate the ability of this assay to detect chemicals requiring azo-reduction; however, they also demonstrate a gap in applicability domain, as MutaMouse PHs elicit a negative response following exposure to Sudan I. Elucidation of the mechanisms underlying this gap will require further study.

This paper reports the development of an ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC‒MS/MS) method to determine eight banned dyes (Sudan I-IV, Sudan Orange, Sudan Red 7B, Para Red, Rhodamine B) in turmeric, curry, and chili products. For this purpose, the feasibility of electrospray (ESI), atmospheric pressure chemical ionization (APCI) and atmospheric pressure photoionization (APPI) for the ionization of these compounds was evaluated. The tandem mass spectrometry (MS/MS) fragmentation of all targeted compounds was studied and both multistage mass spectrometry and high-resolution mass spectrometry were used to establish the fragmentation pathways and identify common fragmentation behaviors. Among the most significant ions, the most characteristic and abundant product ions observed on the triple quadrupole were selected to propose a selective and sensitive UHPLC‒MS/MS method (multiple reaction monitoring mode, MRM) of these target compounds in spices samples after a quick and easy extraction with acetonitrile. Matrix effect (ME) studies carried out in the three atmospheric pressure ionization sources have demonstrated that APCI showed the best performance with ME values ranging from 2 to 25%. Furthermore, the estimated quality parameters indicated the good performance of the proposed method, providing low method limits of detection (MLODs) (1-48 μg kg-1), good intra-day precision (RSD % < 15%), and accurate quantitation (relative error % < 15%). Finally, the applicability of the developed method was demonstrated by the analysis of turmeric, curry, and chili products. In total, 36 diverse samples coming from different countries were analyzed and although none of these compounds were detected above the MLODs, the analysis of spiked samples showed that the method was able to detect this family of compounds at low μg kg-1.

A liquid chromatography/tandem mass spectrometry (LC-MS/MS) method is developed to simultaneously determine 20 synthetic dyes (New Coccine, Indigo Carmine, Erythrosine, Tartrazine, Sunset Yellow FCF, Fast Green FCF, Brilliant Blue FCF, Allura Red AC, Amaranth, Dimethyl Yellow, Fast Garnet GBC, Para Red, Sudan I, Sudan II, Sudan III, Sudan IV, Sudan Orange G, Sudan Red 7B, Sudan Red B, and Sudan Red G) in food samples. This method offers high sensitivity and selectivity through the selection of two fragment ion transitions under multiple reaction monitoring mode to satisfy the requirements of both quantitation and qualitation. Using LC-MS/MS, the newly developed extraction protocol used in this study is rapid and simple and does not require the use of solid-phase extraction cartridges. The linearities and recoveries of the method are observed at the concentration range of 0.10–200 μg/kg and more than 90% for all dyes, respectively. The method has been successfully applied to screen 18 commercial chili powders and six commercial syrup-preserved fruits purchased from retail establishments in Taipei City. The results show that three legal food dyes, Tartrazine, and/or Sunset Yellow FCF, and/or New Coccine, are present in some syrup-preserved fruits. Amaranth, an illegal food dye in certain countries but declared illegal in Taiwan, is found in an imported syrup-preserved fruit.

WOS: 000413291700070, PubMed ID: 29037726, Hybrid nanostructures composed of gamma-Fe2O3 (maghemite) and carboxylated-multi walled carbon nanotube (cMWCNT) were used for the magnetic solid phase extractions and determination of Sudan I, II, III, IV, Para Red, Sudan Black B and Sudan Red 7B in chili products. High performance liquid chromatography (HPLC) was employed for the measurements. Limit of quantification (LOQ) values were found in the range 0.44-2.82 ng mL(-1) for analytes. The best extraction parameters were determined as pH 8.0, 40 mg of magnetic nanoparticle, 4.0 min of contact time, 0.3 mL desorption by acetonitrile. The samples were dissolved in acetone-dichloromethane-methanol (3: 2: 1, v/v/v) and diluted with acetonitrile-methanol (v/v; 80: 20) before the method was applied. Concentrations of Sudan dyes and Para Red were determined in four samples of chili powder from less than LOQ to 31.21 +/- 1.6 ng g(-1), two samples of chili tomato sauces (lower than LOQ) and two samples of ketchup (lower than LOQ)., Mardin Artuklu University [MAU-BAP-14-SHMYO-09], The present work was carried out under the financial support of Mardin Artuklu University (MAU-BAP-14-SHMYO-09).

A sensitive and efficient method was developed for the simultaneous determination of eight synthetic dyes (Chrysoidin, Auramine O, Sudan(I-IV), Para Red, and Rhodamine B) in bean and meat products using high-performance liquid chromatography with tandem mass spectrometry. A simple extraction procedure using acetonitrile has been applied for the extraction of these dyes from spiked bean and meat samples. Chromatographic separation was achieved on a Waters XTerra C18 column (2.1 × 150 mm, 5 μm) with a multistep gradient elution. Detection and quantification were performed using mass spectrometry in multiple reaction monitoring mode. Linear calibrations were obtained with correlation coefficients R(2) > 0.99. The limits of detection and quantification for the eight dyes were in the ranges of 0.03-0.75 and 0.1-2.0 μg/kg depending on matrices, respectively. The recoveries of these dyes in different food matrices were between 71.2 and 116.9% with relative standard deviations

Sudan I, II, III, IV, Para Red, Orange G and Red 7B are synthetic regularly dyes utilized to dye plastics and other manufactured materials. In recent years, concerns about the genotoxic possibilities of Sudan colors have been raised. A few national bodies and food experts consider Sudan dyes to be genotoxic cancer-causing agents while others view these dyes as possible cancer-causing agents. Therefore, it is of the outmost importance to assess the risk and presence of Sudan dyes in Egyptian spices, including; sumac, hot chilli, cumin, paprika, curry and turmeric. A total of 83 samples were collected randomly from different supermarkets and spice shop in various municipalities of Egypt (Cairo, Giza, Qalyubia, Faiyum and Alexandria). For Sudan dyes determination, gel permeation chromatography (GPC) and high-performance liquid chromatography (HPLC) were used. Dyes were extracted from spices with acetonitrile and selectively initial separated by GPC. Fractions were collected from 12 min to 24 min and then determined by HPLC with diode array detection (HPLC-DAD). The method performance was validated on hot chilli samples, and the limit of quantification (LOQ) was 0.1 mg/kg for the seven Sudan dyes. Moreover, other method validation parameters were determined in this work, including linearity, accuracy, recovery, limit of detection (LOD), repeatability, reproducibility and expanded uncertainty. Finally, a market survey was conducted to assess the incidence of such illegal dyes and enlighten buyers, almost 50% of the tested samples were contaminated with Sudan dyes. Sudan Red 7B and Para Red were not detected in the samples, and the mean contamination level varied from 0.01 mg/kg for Sudan Ⅱ to 50.1 mg/kg for Sudan Ӏ. It is recommended to buy raw whole spices – not in powder form- and blend them at home. In addition, spices should be purchased from established retailers, and buyers should avoid spices with abnormally red shading.

The inclusion compounds of iodine such as α-cyclodextrin-KI-I2-4H2O, β-cyclodextrin-KI-I2-H2O, and amylose-iodine are hydrogen bonded with dyes such as Para red, Congo red, Direct red, Bismark brown, Trypan blue, and Evans blue. Hydrogen bonding of these with dyes containing O–H and N–H occurs in glucosidic oxygen atoms or O–H groups of the polysaccharides. Excitons are emitted and absorbed by the electrons along the iodine chains as revealed by the analysis, which reduces band gap along the polyiodide chains.

Sudan dyes (Sudan 1, 2, 3, 4, Para red and Sudan red G) have been banned as food colorants due to their carcinogenicity. This study first synthesized a hapten of Sudan 4 and produced the monoclonal antibody for immunoassay of these red dyes. The hapten was synthesized by coupling 4-amino-3-methylbenzoic acid to o -toluidine to obtain an intermediate hapten and then the intermediate hapten was coupled to β-naphthol to obtain a tentative hapten. The generated monoclonal antibody showed broad specificity to the six Sudan dyes. After evaluation of different coating antigens, a heterologous competitive indirect immunoassay was developed to determine the six red dyes in egg yolk simultaneously. The crossreactivities for the six analytes were in a range of 64%–110% and the limits of detection were in a range of 0.08–0.2 ng/g depending on the compound. Intra- and inter-assay recoveries from the standards fortified blank samples ranged from 71.5% to 107.4% with coefficients of variation lower than 14.6%.

Sudan azo dyes are banned for food usage in most countries, but they are illegally used to maintain or enhance the color of food products due to low cost, bright staining, and wide availability of the dyes. In this report, we examined the toxic effects of these azo dyes and their potential reduction metabolites on 11 prevalent human intestinal bacterial strains. Among the tested bacteria, cell growth of 2, 3, 5, 5, and 1 strains was inhibited by Sudan I, II, III, IV, and Para Red, respectively. At the tested concentration of 100 μM, Sudan I and II inhibited growth of Clostridium perfringens and Lactobacillus rhamnosus with decrease of growth rates from 14 to 47%. Sudan II also affected growth of Enterococcus faecalis. Growth of Bifidobacterium catenulatum, C. perfringens, E. faecalis, Escherichia coli, and Peptostreptococcus magnus was affected by Sudan III and IV with decrease in growth rates from 11 to 67%. C. perfringens was the only strain in which growth was affected by Para Red with 47 and 26% growth decreases at 6 and 10 h, respectively. 1-Amino-2-naphthol, a common metabolite of the dyes, was capable of inhibiting growth of most of the tested bacteria with inhibition rates from 8 to 46%. However, the other metabolites of the dyes had no effect on growth of the bacterial strains. The dyes and their metabolites had less effect on cell viability than on cell growth of the tested bacterial strains. Clostridium indolis and Clostridium ramosum were the only two strains with about a 10 % decrease in cell viability in the presence of Sudan azo dyes. The present results suggested that Sudan azo dyes and their metabolites potentially affect the human intestinal bacterial ecology by selectively inhibiting some bacterial species, which may have an adverse effect on human health.

Many methods have been reported to determine the residues of Sudan dyes in food samples. Among the reported methods, enzyme-linked immunosorbent assay (ELISA) was a frequently used practical screen tool. In this study, a novel hapten of Sudan 2 was synthesized by coupling 4-amino-3-methylbenzoic acid to β-naphthol, and the monoclonal antibody against Sudan 2 was produced. The obtained antibody can recognize Sudan 1, 2, 3, and 4, Sudan red G, and Para red simultaneously. After evaluation of different coating antigens, a heterologous indirect competitive ELISA was then developed to determine the six Sudan dyes in egg. The cross-reactivities for the six analytes were in a range of 63% to 100%, and the limits of detection were in a range of 0.2 to 0.5 ng/g, depending on the compound. Intra- and interassay recoveries from the standard fortified blank eggs were in a range of 71.7% to 97.6% with coefficients of variation lower than 17.1%.

Azo dyes para red was synthesized. The products were characterized by FTIR and UV-Visible spectrophotometers. The antibacterial activities of the compounds were studied using gram positive and gram negative microorganism.

Different nitrates were used as sources of nitrosonium ion to obtain diazonium salts. Diverse azo compounds were synthetized in acetonitrile giving very good yields and free of by-products in comparison with traditional synthesis. Among the tested species, the best combination for para red synthesis was nitric acid and gaseous hydrogen chloride.

A liquid–liquid extraction method was developed for purifying and enriching the sample of 6 azo-dyes (including Para red, Sudan red G, Sudan I, Sudan II, Sudan III and Sudan IV) by formic acid and chloroform. The results indicated that formic acid can facilitate the solution of fat-soluble azo-dyes, which was helpful for the separation of the fat-soluble interferences from the samples. The extracting conditions of 6 azo-dyes were also optimised. And the proposed extraction method was evaluated by the determination of 6 azo-dyes in chilli products. The mean recoveries of 6 azo-dyes were from 94.1% to 99.2% for chilli powder and from 94.2% to 98.6% for chilli spice. The CC α and CC β obtained for 6 azo-dyes were in the range of 1.7–2.1 and 2.8–3.4 μg/kg for chilli spice and chilli powder. The inexpensive and simple method was acceptable for routine monitoring 6 azo-dyes in chilli products.

To obtain antibodies to develop an enzyme-linked immunosorbent assay (ELISA) for the analysis of Sudan red I, haptens were designed and synthesized via four different strategies: (i) attachment of a spacer at the para position of the benzene ring, (ii) attachment of a spacer at the naphthol part, (iii) attachment of a spacer at the hydroxyl group of the Sudan red I molecule, and (iv) use of a fragment of the target molecule. A total of 10 haptens were used to generate immunogens, coating antigens, and polyclonal antibodies. One of the heterologous ELISAs developed exhibited an IC 50 of 1.6 ng/ml, a limit of detection (LOD) of 0.03 ng/ml, and a dynamic range between 0.1 and 14 ng/ml. The assay had 13% cross-reactivity with Para red and negligible cross-reactivity with other structure-related compounds. This ELISA was much more specific than those published previously. This assay was used to determine Sudan red I residues in tomato sauce and chili powder samples after simple pretreatment. The results were validated by comparison with high-performance liquid chromatography (HPLC). The average recoveries of Sudan red I by ELISA and HPLC were in ranges of 70–97% and 82–114%, respectively, indicating suitability of the developed ELISA for screening of Sudan red I in foods.

Sudan azo dyes have genotoxic effects and ingestion of food products contaminated with Sudan I, II, III, IV, and Para Red could lead to exposure in the human gastrointestinal tract. In this study, we examined thirty-five prevalent species of human intestinal bacteria to evaluate their capacity to degrade Sudan dyes and Para Red. Among these tested bacterial strains, 23, 13, 33, 30, and 29 out of 35 species tested were able to reduce Sudan I, II, III, IV, and Para Red, respectively, to some extent. Bifidobacterium infantis, Clostridium indolis, Enterococcus faecalis, Lactobacillus rhamnosus, and Ruminococcus obeum were able to reduce completely all four tested Sudan dyes and Para Red. Escherichia coli and Peptostreptococcus magnus were the only two strains that were not able to reduce any of the tested Sudan dyes and Para Red to any significant extent. Metabolites of the reduction of the tested Sudan dyes and Para Red by E. faecalis were isolated and identified by HPLC and LC/ESI-MS analyses and compared with authentic standards. Thus it appears that the ability to reduce Sudan dyes and Para Red except Sudan II is common among bacteria in the human colon.

Matrix solid-phase dispersion (MSPD) with alumina N as adsorbent has been used for extraction of para red, Sudan 1, Sudan 2, Sudan 3, and Sudan 4 dyes from egg yolk. The extracts were analyzed by ultra-performance liquid chromatography–tandem mass spectrometry (UPLC–MS–MS). Mean recovery for the five dyes ranged from 63.2 to 98.6%, with CV 0.55–10.00%. One sample was confirmed to contain 0.3 mg kg−1 Sudan 4.

A simple, sensitive and reliable UPLC method was developed and validated for the simultaneous determination of six Sudan dyes (Sudan Red G, Sudan I, II, III, Sudan Red 7B, Sudan IV) and Para Red in duck muscle and egg samples. Samples were extracted with acetonitrile, then the extract was dried under rotary evaporation and dissolved in acetonitrile/0.1% formic acid (85:15, v/v). Chromatographic separation was achieved on an Acquity UPLC BEH C18 column under gradient conditions. Samples were detected using a diode array detector set to 480 and 500 nm. The method was validated with respect to linearity, accuracy, precision, and specificity.

An automated, confirmatory and sensitive procedure has been developed and validated for the determination of Sudan (I-IV), Sudan Orange G, Sudan Red 7B and Para Red in hot chilli food samples. The proposed method includes pressurised liquid extraction (PLE) with acetone, gel permeation chromatography (GPC) clean-up and detection by liquid chromatography (LC) coupled to electrospray ionization in positive mode tandem mass spectrometry (ESI-MS-MS). The main parameters affecting the performance of the different ionization sources and PLE parameters were previously optimised using statistical design of experiments (DOE). The method was in-house validated on chilli powder and chilli meat. Linear calibrations were obtained with correlation coefficients R(2)>0.999. The limits of detection (LOD) and quantification (LOQ) of the method were in the ranges of 0.002-0.012 ng g(-1) and 0.006-0.036 ng g(-1), respectively for chilli powder. The decision limit and detection capability were between 0.005-0.022 ng g(-1) and 0.007-0.026 ng g(-1), respectively for chilli meat. Recoveries ranged from 94% to 105%. The applicability of the method to the determination of azo-dyes in hot chilli products was demonstrated.

A high-throughput mass spectrometric method is presented for the simultaneous detection of Sudan I, II, III, IV, and Para-Red azodyes in foodstuff. The method is based on the use of deuterium-labeled internal standards and atmospheric pressure chemical ionization (APCI) in a triple-quadrupole instrument. The gas-phase breakdown pattern of each labeled and unlabeled analogue displays the naphthoic moiety as a common fragment. The search for the parents of this common species (parent ion scans) allows, by flow injection and in a single run, the evaluation of the presence of each polluting species spiked in typical foodstuffs. A detailed assay of each azodye was performed by LC-APCI and isotope dilution method, through the multiple reaction monitoring approach, using deuterium-labeled internal standards. Sudan dyes can be quantified above the threshold of 10 ppb except for Sudan Para-Red, for which the limit of quantification was 20 ppb, likely due to the different ionization efficiency.

A sensitive and accurate methodology was developed for the analysis of seven illegal dyes (Sudan I, Sudan II, Sudan III, Sudan IV, Sudan Orange G, Sudan R and Para Red,) used as additives in food products, such as chilli powder and steak sauces. The analytical methodology consisted of solvent extraction with acetonitrile followed by liquid chromatography time-of-flight mass spectrometry detection. Accurate mass measurements were crucial in order to achieve a high degree of specificity for the target analytes in such complex samples. The dyes were effectively extracted from spice and sauce matrices achieving recoveries higher than 75%. Because of the excellent mass accuracy obtained for the target analytes (better than 2 ppm), no cleanup of the samples was required using this methodology, thus leading to a better precision and reproducibility of the results from the quantitative point of view. Calibration curves were linear and covered two orders of magnitude (from 0.01 to 1 mg L−1) for all the compounds s...

A sensitive and cheap high performance liquid chromatography (HPLC) with ultraviolet-visible (UV-VIS) was developed for the determination of Sudan dyes (I, II, III, and IV) residues in various types of eggs. The chromatographic separation was achieved on a reverse phase C18 column with gradient elution, using a mobile phase of 0.1% formic acid acetonitrile/0.1% formic acid aqueous solution; detector was set at 478 nm for Sudan I and 520 nm for Sudan II, III and IV. The suspected egg samples were derivatized with N,O-bis (trimethylsilyl) trifluoro-acetamide and confirmed by gas chromatography-mass spectrometry (GC-MS) in EI. Mass spectra of trimethylsilyl derivatives of the Sudan dyes were built up in EI mode. Recoveries of the Sudan dyes ranged between 79.8 and 95.7% in eggs by HPLC-UV, with all the relative standard deviations of less than 5%. Limit of detection (LOD), limit of quantification (LOQ) were in the range of 4.0-4.8 and 12.3-13.8 microg kg(-1) in eggs, respectively. Identification and confirmation could be validated in the range of 2.0-4.2 microg kg(-1) with the GC-MS method. This method is suitable for routine fast monitoring, screening and confirmation of Sudan dyes residues in eggs, as mandated by regulatory agencies.

A simple and rapid multiresidue method for the determination of nine banned synthetic dyes in various spices has been developed. Reversed phase HPLC coupled with mass spectrometry (tandem in time - ion trap mass analyser) was employed for the examination of crude acetonitrile extract acidified with acetic acid. The detection limits of Para Red, Sudan Orange G, Sudan I, Sudan II, Sudan III, Sudan IV, Sudan Red 7B and Rhodamine B were in the range of 0.02-0.1 mg/kg, the recoveries ranged from 75.7 to 92.3% with repeatability of 0.9-11.3%. Rather worse performance characteristics were obtained with Tropaeolin 000, obviously due to its more polar nature as compared to other dyes involved in this study. In spite of that, the developed method can be used for a reliable control of a wide range of dyes used for illegal colouring of various spices.

A rapid and sensitive ultra-fast liquid chromatography tandem mass spectrometry method, followed by simple protein precipitation and solid-phase extraction, has been developed and validated for the quantitative determination of four azo dyes (Para red, Solvent yellow 2, Solvent red 1 and Sudan red 7B) in rat plasma using D5-Sudan I as the internal standard. The optimal separation was accomplished on an Agilent Eclipse Plus C18 column (100 × 2.1 mm, 1.8 μm) with gradient elution using the mobile phase including acetonitrile and water (containing 0.1% formic acid). The flow rate was 0.45 mL/min. The detection was conducted by means of electrospray ionization mass spectrometry in positive ion mode with multiple reaction monitoring. The calibration curves showed good linearity, with correlation coefficients >0.998 for all of the analytes within the concentration range. The lower limits of quantification (LLOQs) of Para red, Solvent yellow 2, Solvent red 1 and Sudan red 7B in rat plasma were 1.0, 0.1, 0.1 and 0.1 μg/L, respectively. The intra- and interday relative standard deviations were ≤9.6 and ≤12.4%, respectively, and the accuracy was in the range of -5.8 to -9.5%. The average recoveries were between 81.49 and 118.65%, and the matrix effects were satisfactory in the biological matrices. The fully validated method has been successfully applied in measuring levels of the four azo dyes in rat plasma following oral administration of 20.0 mg/kg of analytes in rats, which was suitable for the pharmacokinetic studies of the azo dyes.

A simple and fast analytical method for the determination of sudans I, II, III, and IV in chili- and curry-containing foodstuffs is described. These dyes are extracted from the samples with acetonitrile and analyzed by high-performance liquid chromatography coupled to a photodiode array detector. The chromatographic separation is carried out on a reverse phase C18 column with an isocratic mode using a mixture of acetonitrile and water. An "in-house" validation was achieved in chili- and curry-based sauces and powdered spices. Depending on the dye, limits of detection range from 0.2 to 0.5 mg/kg in sauces and from 1.5 to 2 mg/kg in spices. Limits of quantification are between 0.4 and 1 mg/kg in sauces and between 3 and 4 mg/kg in spices. Validation data show a good repeatability and within-lab reproducibility with relative standard deviations < 15%. The overall recoveries are in the range of 51-86% in sauces and in the range of 89-100% in powdered spices depending on the dye involved. Calibration curves are linear in the 0-5 mg/kg range for sauces and in the 0-20 mg/kg range for spices. The proposed method is specific and selective, allowing the analysis of over 20 samples per working day.

Azo dyes, extensively used for coloring a variety of consumer goods, such as leather, clothes, food, and toys, can under certain conditions be reduced to form confirmed or suspected carcinogenic aromatic amines. This article gives an overview of the state of development of analytical procedures for the determination of such azo dyes, which are banned by the European Commission.

The Commission Decision of EC dated 20 June 2003, on emergency measures concerning hot chilli and hot chilli products coming into any EC member state, required that the consignments of such products should be accompanied by an analytical report showing that they are free of artificial dye Sudan I. The opportunity to set a confirmatory method is evident, and the paper proposes a HPLC/APCI-MS method useful for identification and quantitation of Sudan I, also at very low levels in hot chilli, other spices, and oven-baked foods. Validation data are reported.