PROOF COVER SHEET Journal acronym: TFAC Author(s): Mannan Hajimahmoodi, Mahdi Afsharimanesh, Ghazaleh Moghaddam, Naficeh Sadeghi, Mohammad Reza Oveisi, Behrooz Jannat, Elham Pirhadi, Fatemeh Zamani Mazdeh and Hossein Kanan Article title: Article no: Enclosures: Determination of eight synthetic dyes in foodstuffs by green liquid chromatography 774465 1) Query sheet 2) Article proofs Dear Author, 1. Please check these proofs carefully. It is the responsibility of the corresponding author to check these and approve or amend them. A second proof is not normally provided. Taylor & Francis cannot be held responsible for uncorrected errors, even if introduced during the production process. Once your corrections have been added to the article, it will be considered ready for publication. Please limit changes at this stage to the correction of errors. You should not make insignificant changes, improve prose style, add new material, or delete existing material at this stage. 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Food Additives & Contaminants: Part A, 2013 Vol. 00, No. 00, 1–6, http://dx.doi.org/10.1080/19440049.2013.774465 Determination of eight synthetic dyes in foodstuffs by green liquid chromatography Mannan Hajimahmoodia*, Mahdi Afsharimanesha, Ghazaleh Moghaddama, Naficeh Sadeghia, Mohammad Reza Oveisia, Behrooz Jannatb, Elham Pirhadic, Fatemeh Zamani Mazdehc and Hossein Kanana a 5 Department of Drug and Food Control, Faculty of Pharmacy, Tehran University of Medical Sciences, Tehran, Iran; bFood and Drug Laboratory, Research Center, Ministry of Health and Medical Education, Tehran, Iran; cFood and Drug Administration, Tehran University of Medical Sciences, Tehran, Iran (Received 21 October 2012; final version received 21 January 2013) 10 15 20 Eight synthetic food colours were analysed by green liquid chromatography. Green liquid chromatography is an environmentally friendly technique which does not use organic solvents in the extraction procedure or in the chromatographic method. Analysis was carried out for the following colours: tartrazine (E102), indigotine (E132), Quinoline Yellow (E104), Ponceau 4R (E124), Sunset Yellow (E110), Brilliant Blue (E133), Allura Red (E129) and carmoisine (E122) in four different foods: cookies, coloured rice, saffron and fruit juice. The method was performed on an Eurospher-100 C8 (5 μm, 4.6 × 250 mm) column with ultraviolet (UV)-VIS detection and validated by determining the calibration lines, measurement of recovery, precision, and limits of quantification and detection (LODs and LOQs). LOD ranged from 0.04 mg kg–1 for E102 to 1.00 mg kg–1 for E132; LOQ ranged from 0.06 mg kg–1 for E102 to 1.12 mg kg–1 for E122. The levels of colours in foods were compared with Iranian National Standards, but only 7.5% of cookies, 30% of coloured rice, 8% of saffron and 12% of juice samples were in compliance with these standards. Tartrazine is prohibited in Iran, but it was found as the most prevalent food colour in the samples analysed. The results of these tests confirmed that HPLC avoiding the use of organic solvents is a suitable method and can be used for quantitative analyses or screening of food samples for synthetic food colours. Keywords: green chromatography; synthetic dye; HPLC analysis 25 30 AQ1 35 40 45 Introduction Currently, analytical methods are used for environmental monitoring. However, a paradoxical situation has emerged because most of the analytical methodologies employed to investigate environmental problems themselves generate chemical waste, resulting in an environmental impact. Consequently, the aim of green chemistry has been focused on the development of methodologies less harmful to humans and the environment. Green analytical chemistry is at an early stage of development, but there is a clear trend towards fast and consistent growth (Vidotti et al. 2005). Food colours are usually added to various commercial food products in order to make them appear more attractive and to achieve the desired colour. Food colours can be divided into four categories: natural, nature-identical, inorganic and synthetic (Aberoumand 2011). For safety reasons there have been recent reductions in the number of permitted food colours but they are still being used all over the world because of their low price, effectiveness and stability. Moreover, the food processing industry uses all types of food colours, but to minimise potential toxicity the amounts of permitted synthetic colours used are strictly limited (Huang et al. 2005; Hajimahmoodi et al. 2008). *Corresponding author. Email: [email protected] © 2013 Taylor & Francis Regulations for permitted edible food colours are applied nationally and may vary from country to country. In Iran there are seven permitted synthetic food colours, including: indigotine (E132), Quinoline Yellow (E104), Ponceau 4R (E124), Sunset Yellow (E110), Brilliant Blue (E133), Allura Red (E129) and carmoisine (E122). The use of tartrazine (E102) is prohibited in Iran, although in fact it was the most prevalent colour determined in food samples in this study. Therefore, an accurate and reliable method is needed to measure synthetic food colours to protect consumer health. Ion-pair extraction (Van Peteghem and Bijil 2010), adsorption on solid materials such as alumina or polyamide (Kirschbaum et al. 2006) has been used for colorant extraction depending on food type and the chemical structure of the colour. TLC (Lotfi et al. 2008), adsorptive voltammetry (Florian et al. 2002), spectrometry (Oveisi et al. 2003), derivative spectrometry (Gianotti et al. 2005), and capillary electrophoresis (Huang et al. 2005; Ma et al. 2006) can be used for quantitative analysis of colorants, but reversed-phase liquid chromatography (Zatar et al. 2007), capillary electrophoresis (Huang et al. 2005), and ion-pair chromatography (Zatar 2007) are still the most widely used methods. 50 55 AQ2 60 65 AQ3 2 70 75 80 85 M. Hajimahmoodi et al. Techniques evaluated in this article were carried out by green chromatography, which is a general, accurate and safe analytical method. Smaller amounts of toxic organic solvents were used in this method than in previous research (Khanavi et al. 2011). Analysis was carried out on food samples consisting of cookies, coloured rice, saffron and fruit juice. Samples of cookies and juice had the highest levels of colouring. Saffron, with its charming fragrance and delightful taste, is one of the most valuable herbs in Iran, which accounts for 90% of the world’s saffron production (Moghaddasi 2010). In Iran rice is nearly always decorated with saffron. The main aim of this study was to evaluate uses of food colours in terms of a market survey for identification and quantification. Materials and methods Chemicals and reagents 90 95 100 The following solid standards were donated by Iran’s Institute of Standards and Industrial Research: E102, E104, E124, E110, E133, E122, E129 and E132; their purities were ≥ 98%. They were dried at 65°C for 6 h, then individually dissolved in deionised water at a stock concentration of 1 mg ml−1. Polyamide powder (grain size < 0.16) and other chemicals were of analytical grade and purchased form Merck (Darmstadt, Germany). Samples Samples were divided into four groups (fruit juice, saffron, coloured rice and cookie); each group under evaluation consisted of 25 samples. These samples had been collected from restaurants, confectioneries and groceries; they were stored as recommended on their labels and analysed before expiration dates. Sample preparation 105 110 115 Totals of 10 ml of each juice sample, 5 g of coloured rice or saffron samples were taken and first diluted with deionised water (1:1). The solid samples (coloured rice and cookies) were transferred to a flask separately, mixed with 30 ml NH3, centrifuged for 5 min at 1800 rpm and then the liquid phase (supernatant) separated. Polyamide adsorbent (2 g) was added to the liquid extract and then the mixture was stirred vigorously to adsorb all the colorants in the solution (if the solution was still coloured, polyamide adsorbent (1 g) should be added). pH levels of the solutions were adjusted to 3 with HCl (10% v/v), filtered and then the adsorbent was washed three times with 20 ml distilled deionised water. The filtered adsorbent was then transferred to a 100 ml beaker, 20 ml solution of NH3 (25% w/v) was added and filtered again. The procedure was repeated twice to remove all the colour from the polyamide. The collected solution was dried out on a boiling water bath and the whole residue was transferred to a 10-ml volumetric flask using mobile phase. Then it was filtered through a 0.45 μm membrane material filter before HPLC analysis (Khanavi et al. 2011). The preparation of liquid samples (saffron and juice) were initiated by adding HCl 10% and then the same procedure was followed as mentioned above for solid samples. Analysis was carried out using calibration curves and confirmed by standards for each dyes in the HPLC. Thin layer chromatography (TLC) TLC is the official Iranian standard method, but it is not fit for determination purposes. Whatman chromatographic paper No. 3 was used to separate colorants. The mobile phase consisted of an equal volume of NH3 (0.25% w/v) and NaCl (1% w/v). The paper (20 × 20 cm) was marked with each of the standard colours allowing about a 2.0 cm minimum distance between each different spot. The chromatography paper was placed into a 250 ml beaker. The beaker served to hold the solvent; it was filled to a depth of 3–7 mm (10 ml of mobile phase). Lastly, the beaker was covered with a watch glass to prevent the solvent vapours. Liquid chromatographic analysis Samples were analysed by a Knauer HPLC (Germany) system which consisted of a binary pump, a degasser, an automated injector, a column oven and an ultraviolet (UV) detector. The system was controlled by Eurochrom 2000 software. Since all eight colours tested in the study are not usually present in foodstuff simultaneously, a different strategy and approach that involved two different HPLC conditions for the separation of these dyes were used (Khanavi et al. 2011). Chromatographic conditions were evaluated and optimised using a Eurospher-100 C8 (5 μm, 4.6 × 250 mm) column. Before analysis, the temperature of the column was set at 35°C and was conditioned making the mobile phase flow through the system for 30 min at 1.0 ml min−1. The mobile phase was prepared by dissolving 0.25 ml of Triton X-100 up to 100 ml with 50 mmol phosphate buffer solution adjusted to pH 7 and the solution was filtered through a 0.45 µm membrane filter. Due to polarity of the analytes, two different solvent gradient systems (A and B) were employed to accomplish a quick separation of the colours under analysis (Table 1). After identifying the colour present in each sample by TLC the most suitable method for each sample was selected. 120 125 130 135 140 145 150 155 160 165 Food Activities & Contaminants: Part A 3 Table 1. Methods of the colour standard solutions. Method A Method B Colour E number Detection wavelength (nm) Retention time (min) Flow rate (ml min–1) Tartrazine Quinoline Yellow Ponceau 4R Brilliant Blue Allura Red Carmoisine Indigotine Ponceau 4R Sunset Yellow Allura Red Carmoisine E102 E104 E124 E133 E129 E122 E132 E124 E110 E129 E122 450 450 630 630 515 515 600 450 450 515 515 2.103 5.634 7.818 12.409 20.120 33.256 4.017 7.761 10.436 20.120 33.256 1.5 1.5 1.5 1.5 2.25 2.25 1.5 1.5 1.5 2.25 2.25 Results and discussion 170 175 180 185 190 AQ4 195 AQ5 200 205 Iranian National Standards have some stringent rules for regulating the use of food colouring additives and only seven synthetic colours are permitted under these regulations. However, methods to evaluate levels of colouring in food for quality control are currently made by the TLC method. Therefore, based on the achieved results, it seems that approved standards need to be revised both in terms of colour type and related quantitative limitations made regarding further risk assessments. Figure 1 shows the separation of a mixture of edible colours which was actually found in one randomly selected juice sample, including the prevalent Iranian edible colours. Some important method validation parameters are presented in Table 2. Results for correlation coefficients were always > 0.995 and closer to unity showing a good relationship between peak areas and concentrations. Detection limits of colours in the samples were also found to be satisfactory. The ADI of a food additive is determined from an estimated amount of that food additive expressed on a body weight basis that can be ingested daily over a lifetime without any appreciable health risk. Table 2 presents corresponding ADIs as set by the FAO/WHO (1999), the European Food Safety Authority (EFSA 2009) and it also shows the percentages of each colour in juice, coloured rice, saffron and cookie. Tartrazine is commonly understood to contribute to several health problems; it is therefore a prohibited food colour in Iran Standards (Beseler 1999; Iran-Standard 2012). However, according to these tests tartrazine was the most commonly used colour in all four studied groups, with a prevalence of 92% in saffron solution, 88% in juice, 60% in coloured rice and 59% in cookie samples (Table 2), but there were low percentages of indigotine and Allura Red detected in the studied samples. Lok et al. (2010) found that tartrazine and Sunset Yellow were also the most common synthetic colourings used in Hong Kong. To check the accuracy of the method, different kinds of matrices were spiked with the analyte of interest at intermediate concentrations of the each calibration curves. The concentrations were recalculated from the corresponding calibration straight line (experimental concentration) and were compared with the theoretical concentrations. Recovery was estimated as the relationship between the experimental and the theoretical concentration expressed as a percentage: (Cexp/Ctheo) × 100. Table 3 presents the recoveries level of four groups of samples. The recoveries (n = 6) ranged from 93.5 ± 0.9% to 99.7 ± 1.2%. Precision accuracy showed good standard deviations and recovery values. The mean concentration of colours in each sample group is presented in Table 4. All studied colours were present in the juice group, but carmoisine (208 ± 65.3 mg kg–1) and indigotine (5.00 ± 0.83 mg kg–1) recorded the highest and lowest amounts for colour additives, respectively. Research by Ma et al. (2006), carried out in China, reported that tartrazine, Ponceau 4R and Sunset Yellow contents in soft drinks were 10.52 ± 0.91, 2.44 ± 0.41 and 11.71 ± 0.93 mg kg–1, respectively, records which were lower than the colour contents in juice samples tested in this study (Table 4). Other research in Taiwan showed that tartrazine was the most prevalent colour used in soft drinks; Brilliant Blue at a level of 0.6 mg kg–1 and Allura Red at a level of 67.1 mg kg–1 had the highest and lowest concentrations (Huang et al. 2005). According to Brazilian legislation, maximum allowable concentrations of Sunset Yellow, Allura Red and tartrazine are set at 100 mg kg–1 in soft drinks (Pereira Alves et al. 2008). Therefore, according to these Brazilian Standards, these three dyes in the juice samples tested in this study could be approved, but the amounts of carmoisine were higher than the permitted level. Saffron has been used as a spice and colouring agent for many centuries, especially in Iran, and it is known to have numerous medicinal properties (Moghaddasi 2010). Crocin (C44 H64 O24) is the most significant substances providing the colouring power of saffron. It is a rare 210 215 220 225 230 235 240 245 4 M. Hajimahmoodi et al. 1 2 Figure 1. HPLC chromatogram of mixed colours which was actually found in one randomly selected juice sample by: 1. Method A: (tartrazine, Quinoline Yellow; Ponceau; Brilliant Blue; Allura Red; carmoisine); and 2. Method B: (indigotine; Ponceau; Sunset Yellow; Allura Red; carmoisine). Table 2. Linear range, coefficient of determination (R2), ADI permitted colours (mg kg–1 of body) and percentages of each dyes in studied sample (%). Colour Tartrazine Ponceau 4R Brilliant Blue Carmoisine Sunset Yellow Quinoline Yellow Indigotine Allura Red 250 Linear range (ppm) R2 ADI (mg kg–1 bw–1) Juice (%) Coloured rice (%) Saffron (%) Cookie (%) 0.5–2.5 1–20 2–25 2–25 1–10 2–15 1–10 1–15 0.9923 0.9971 0.9996 0.9908 0.9984 0.9974 0.9952 0.9980 0–7.5 0–4.0 0–12.5 0–4.0 0–1 0–0.5 0–5.0 0–7.0 88 40 40 52 40 24 8 8 92 4 − − 20 12 − − 60% − − − 20% 10% − − 59 − 7 7 29 55 − − carotenoid found in nature which can easily dissolve in water. In comparison with other carotenoids, crocin has a wider application as a colour in food and medicine, mainly because of its high solubility. As saffron is the world’s most expensive spice, a dishonest producer may adulterate saffron by adding a similar looking material or a yellow dye to give the saffron the appearance of good quality. Pure saffron contains only the stigma of the crocus flower Food Activities & Contaminants: Part A 5 Table 3. LOD, LOQ and recoveries of the edible dyes fortified to cookie, coloured rice, saffron and juice samples. Dyes Allura Red Indigotine Quinoline Yellow Sunset Yellow Carmoisine Brilliant Blue Ponceau Matrices Juice Juice Cookie Spiked level 8 5 8 Recovery (n = 6) 99.0 ± 0.5 98.9 ± 0.8 96.6 ± 0.6 0.45 0.06 0.40 LOD (mg kg–1) LOQ (mg kg–1) 0.92 0.11 0.46 Table 4. Saffron 5 93.5 ± 0.9 0.15 0.22 Juice 13 99.7 ± 1.2 1.00 1.12 Juice 13 98.3 ± 0.2 0.60 0.65 Tartrazine Juice Coloured rice 10 1 97.0 ±0.4 98.1 ± 0.4 0.23 0.04 0.29 0.06 Mean and range of dye concentrations (mg kg–1) in studied samples. Colour: Sample Tartrazine Ponceau Brilliant Blue Carmoisine Sunset Yellow Quinoline Yellow Indigotine Allura Red Juice Mean 24.42 22.89 24.85 208.57 25.49 5.24 Range 0.06–121.82 0.37–187.72 2.75–71.44 11.9–603.14 0.48–215.14 0.8–13.79 2.46 6.46 1.93–3.00 5.77–7.15 Saffron Mean 56.55 0.60 Range 0.04–129.69 0.60 n.d. – n.d. – 2.14 0.94–4.81 44.8 0.84–73.10 n.d. – n.d. – Coloured Rice Mean 9.66 Range 0.20–38.01 n.d. – n.d. – n.d. – 3.297 0.24–7.03 27.027 n.d. 10.23–43.82 – n.d. – Cookie n.d. – 0.95 0.90–0.99 3.75 2.21–5.28 6.30 0.08–28.29 19.77 0.61–96.36 n.d. – Mean 4.66 Range 0.13–17.36 n.d. – Note: n.d., Not detected. 255 260 265 270 275 280 with nothing else added. Therefore, related yellow synthetic dyes in saffron must be considered in evaluations of purity in saffron. Adulteration of saffron, especially by synthetic dyes, has not only an economic impact, but also may have direct pharmacological and toxicological consequences (Alonso et al. 1998; Fernandez 2004). In view of the diversity of fraudulent methods, the purity of saffron from the field down to the consumer is important. Chromatographic analyses showed evidence of the colours tartrazine, Ponceau, Sunset Yellow and Quinoline Yellow in saffron samples tested in this study and that tartrazine with a mean concentration of 56 ± 39.9 mg kg–1 was the most predominantly used colorant. In Iran rice is usually decorated with saffron and its high price contributes to the use of synthetic colour for dying rice. Additives of synthetic dyes that were found in samples of coloured rice were tartrazine, Quinoline Yellow and Sunset Yellow, of which Quinoline Yellow had the record for the maximum amount with a mean concentration of 27 ± 18.25 mg kg–1. Concentrations of evaluated colours in cookies were lower than those in other sample groups, but in spite of the low amount of detected colours they had diverse colour types after the juice samples. Quinoline Yellow and Brilliant Blue with mean concentrations of 19 ± 9.5 and 0.95 ± 0.31 ppm were the lowest and highest records of colour in cookie samples, respectively (Table 4). In Greece, food colour contents were determined by reversed-phase HPLC. Apart from Quinoline Yellow and carmoisine as exceptions, all sweets had higher colour concentrations than cookie samples in this study (Minioti et al. 2007). Rao and Bhat (2003) studied 218 cookie samples taken from the city and the countryside. In this research only 38% of samples from the city and 39% of samples from the countryside met the Indian Standard, which is 100 ppm (maximum) for all determined food colorants. In a study by Guler (2005) in which synthetic colours were evaluated in confectionary and powder drinks, 45% of whole samples had more than the approved amounts of colorant under Turkish standards. The TLC technique is the approved standard method for food colour evaluation in Iran, but it does not provide an accurate quantification method (Iran-Standard 2012). Iranian Standard numbers for different materials (saffron solution A-1-259, orange juice 507, Cherry juice 5528, Barberry juice 2736, multi-fruit juice 507, coloured rice 259, cookie 3493) recommend that there must be no trace of synthetic colours in current unbranded products. According to these above-mentioned standards, most of the analysed samples in this study were rejected and just 7.5% of cookies, 30% of coloured rice, 8% of saffron and 12% of juice were approved. Compared with other countries, Ponceau 4R is prohibited in the United States and Norway. Brilliant Blue is prohibited in many countries including Belgium, France, Germany, Switzerland, Sweden, Austria and Norway. Tartrazine is also forbidden in the United States and Austria (Vachirapatama et al. 2008). However, countries 285 AQ6 290 295 300 305 310 6 315 320 M. Hajimahmoodi et al. have different restrictions. Regarding Japanese standards for food additives, Brilliant Blue, indigo carmine, amaranth, erythrosine, Allura Red, Sunset Yellow and tartrazine are permitted without any restrictions (Specifications and food standards, food additives 2011). Synthetic colours are used in Hong Kong; they follow the Codex Alimentarius Commission of the FAO/WHO, which is currently being updated (Lok et al. 2010). Conclusion 325 330 There have been problems with Iranian National Standards for regulating the use of food colorants in terms of determining food colouring types and quantitative limitations. Therefore, it is necessary to revise standards and introduce a reliable quantitative method to control food quality. 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