Occurrence of Sudan I in Paprika Fruits Caused by Agricultural

Apr 15, 2014 - Detailed surveys on Sudan dyes I−IV in paprika fruits, soils, and agronomic ... KEYWORDS: paprika fruit, Sudan I, agricultural enviro...
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Occurrence of Sudan I in Paprika Fruits Caused by Agricultural Environmental Contamination Yunhe Lian,† Wei Gao,*,‡ Li Zhou,† Naiying Wu,§ Qingguo Lu,‡ Wenjie Han,‡ and Xiaowei Tie# †

Hebei Engineering Technology Research Center of Natural Pigments, Handan 057250, Hebei, People’s Republic of China Chenguang Biotech Group Limited Corporation, Handan 057250, Hebei, People’s Republic of China § School of Science, Hebei University of Engineering, Handan 056038, Hebei, People’s Republic of China # Eurofins Scientific Group, Suzhou 215000, Jiangsu, People’s Republic of China ‡

S Supporting Information *

ABSTRACT: Current research has demonstrated the presence of sub parts per billion levels of Sudan dye in paprika fruits during the vegetation process, which is difficult to understand on the basis of the conventional concept of cross-contamination or malicious addition. Detailed surveys on Sudan dyes I−IV in paprika fruits, soils, and agronomic materials used from seven fields of Xinjiang (China) were conducted to investigate the natural contamination. Results revealed that Sudan dyes II−IV were never detected and that Sudan I existed in almost all samples except for the mulching film and irrigation water. The higher total amount of Sudan I in soils, pesticides, and fertilizers compared to coated seeds indicated the combination of Sudan I-contaminated soils and application of Sudan I-containing agronomic materials constitutes a major source of 0.18−2.52 μg/kg levels of Sudan I in fruits during the growth period. The study offers a more reasonable explanation for the previously observed Sudan I in paprika fruits. KEYWORDS: paprika fruit, Sudan I, agricultural environment, agronomic materials, UPLC-MS/MS, GPC

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INTRODUCTION Sudan dyes I−IV are attractive as coloring additives in foodstuffs due to their intense red-orange color (Figure 1).1

Various analytical methods for the determination of Sudan dyes have been developed, including high-performance liquid chromatography (HPLC) with different detectors,7−11 liquid chromatography−mass spectrometry (LC-MS),12−14 enzyme immunoanalysis,15−17 voltammetric techniques,18 and chemiluminescence flow injection analysis.19 Among them, LC-MS/ MS displays outstanding advantages in both rapidly identifying Sudan dyes and accurately quantitating the amount at ultratrace levels. As the detection level was lowered through innovative techniques, more and more incidents involving Sudan dyes at sub parts per million levels were documented in recent years. For example, the 2011 RASFF (Rapid Alert System for Food and Feed) annual report showed that, of 18 entries with detections of Sudan dye (mainly Sudan dyes I and IV) in different foodstuffs, 13 samples measured showed only lowlevel ranges of 0.1−3.8 mg/kg.20 Among a total of 21 samples of various spices and foodstuffs analyzed, 15 of them were found to contain Sudan dye I, III, or IV at low concentrations in the range of 0.0033−0.87 mg/kg.21 With the increasing presence of Sudan dyes at milligram per kilograms levels, it is inevitable for researchers to be focused on the contamination source in the context of reducing the levels where possible. Until now, their presence is ascribed to two possible explanations: either illegal addition or cross-contamination. Generally, levels of several 100−1000 mg/kg of Sudan dyes are needed to enhance the color of paprika and paprika

Figure 1. Chemical structures of Sudan dyes I−IV.

However, Sudan dyes have been classified as category 3 carcinogens by the International Agency for Research on Cancer,2 and thus Sudan dyes are not allowed as food additives in most countries, including the European Union and China.3−6 Consequently, monitoring and controlling the abuse of Sudan dyes in foodstuffs is of great importance for guaranteeing the safety of consumers. © 2014 American Chemical Society

Received: Revised: Accepted: Published: 4072

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Table 1. Major Analytical Performance of the Method for Paprika Fruit matrix-matched regression eqa

R2

linear range (μg/kg)

LOD (μg/kg)

LOQ (μg/kg)

RSDb (%)

Sudan I

Y = 647.19X + 6.99

0.9991

0.1−20

0.06

0.09

7.25

Sudan II

Y = 352.16X + 1.74

0.9994

0.1−20

0.05

0.15

9.58

Sudan III

Y = 616.15X + 15.15

0.9990

0.1−20

0.08

0.22

12.38

Sudan IV

Y = 44.64X + 32.71

0.9996

0.1−20

0.12

0.31

10.21

analyte

a

recoveryc (%) 84.0 ± 4.72 (0.4), 87.2 89.6 ± 2.83 (10.0) 85.7 ± 7.18 (0.4), 84.3 91.5 ± 6.08 (10.0) 81.6 ± 3.15 (0.4), 70.4 82.3 ± 4.97 (10.0) 80.0 ± 5.32 (0.4), 82.5 84.8 ± 3.45 (10.0)

± 6.85 (4.0), ± 5.13 (4.0), ± 5.32 (4.0), ± 3.17 (4.0),

Where X is the mass concentration (μg/kg) and Y is the peak area. bRelative standard deviation, n = 5, c = 5 μg/kg. cMean ± SE, n = 3.

Table 2. Mean Concentrations of Sudan I in Paprika Stem and Fruit Samples Prepared Independently from Different Fields (Mean ± SE, n = 3) paprika fruit/maturation stage field

paprika type

1 2 3 4 5 6 7

urn urn bell urn urn line urn

paprika species C. C. C. C. C. C. C.

f rutescens f rutescens annuum f rutescens f rutescens f rutescens f rutescens

stem (μg/kg) 1.49 0.84 c  1.32 1.04 2.49

a

green (80 days) (μg/kg)

± 0.07b ± 0.05

± 0.02 ± 0.02 ± 0.03

0.76 0.28 0.51    1.59

± 0.04 ± 0.01 ± 0.02

± 0.10

orange (86 days) (μg/kg) 1.10 0.10 0.22 2.06 0.63 0.33 2.52

± ± ± ± ± ± ±

0.07 0.04 0.01 0.14 0.03 0.02 0.21

red (95 days) (μg/kg) 0.68 0.26 0.18 0.63 1.08 1.00 0.53

± ± ± ± ± ± ±

0.09 0.03 0.02 0.06 0.13 0.15 0.05

Maturation stage was expressed by the fruit color and days after sowing. bConcentrations are expressed on a dry matter basis. c, means lack of sample.

a

products.22 For this reason, the European Union set 500 μg/kg as an action limit for Sudan dyes in foodstuffs to differentiate between adulterations and cross-contaminations.23 The explanation of cross-contamination can be supported by several observations. Hoenicke reported that Sudan dyes I and IV at milligram per kilogram level were detected in red bags used for drying, transportation, and storage of the paprika pods and in lubricants used for greasing of the extraction plants and, thus, suggested that Sudan dyes detected may result from crosscontamination caused by some materials containing Sudan dyes.24 Similar conclusions of cross-contamination have been reported by RASFF20 and Schummer et al.21 The aim of the present study was to identify the source of the natural contamination of Sudan dyes in paprika fruits by investigating the potential presence of Sudan dyes I−IV and their contents in agricultural materials used. Our results showed that only Sudan I was present and, therefore, we have studied the distribution of Sudan I within the paprika as well as its contamination in some agronomic materials and the soils. This study provides a new insight into re-evaluating the origin of Sudan dyes in paprika fruits and paprika products.

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with an autosampler system (Waters, Milford, MA, USA), coupled to tandem mass spectrometry operated in positive electrospray ionization (ESI+) mode and multiple reactions monitoring (MRM) mode. The data measured were processed with MassLynx V4.1 software. Sample Collection and Preparation. Sample collection was undertaken in seven planting areas (30−50 km apart from each other) in the Xinjiang Uygur Autonomous Region (China). These fields were away from industry and roads and were amended with commercial pesticide (imidacloprid) and fertilizer (chili special-purpose fertilizer) after growth for 7, 30, and 60 days. For each field, paprika samples at three different stages of ripening including green, orange, and red fruits were collected from the same plant at the 80th, 86th, and 95th days after seeding, respectively. Each batch of samples in the same maturation degree comprised three replicates of subsamples from different paprika plants. All of the corresponding paprika stems and soils adhering to the root system (rhizosphere soils) were sampled 95 days after sowing. The sample type and amount are listed in Table 1. In addition, samples of the pesticide, fertilizer, mulching film, coated seed, and irrigation water were collected from farmers in the planting areas. Paprika fruit and stem samples were dried at 80 °C in an oven and then ground using an FW135 universal grinder (Taisite Instrument Co., Ltd., Tianjin, China). Air-dried soils and chemical fertilizers were pulverized and sieved through an 80-mesh stainless steel sieve. All of the dry powdered samples were homogenized and stored in glass bottles at room temperature prior to extraction and analysis. Mulching films were cut finely into 0.4 cm2 fragments using scissors and homogenized awaiting extraction. All samples were stored at room temperature prior to extraction and analysis. Extraction Procedure. Extraction and analysis were conducted using a modification of the method of the European Commission.25 A 5.0 g (fertilizer), 20.0 g (soil, coated seed, and mulching film), 1.0 g (stem and fruit), or 10 mL (irrigation water) aliquot of the sample was transferred into a 250 mL volumetric flask and diluted with 10 mL (60 mL for 20 g samples) of acetonitrile. Thereafter, samples were shaken for 2 min by an XW-80A model vortex apparatus (Jingke Co., Ltd., Shanghai, China) and then extracted in an ultrasonic bath (TH-300B model ultrasound cleaner, Tianhua Ultrasound Instrument Co., Ltd., Jining, China) for 10 min (30 min for 20 g samples). After

MATERIALS AND METHODS

Reagents and Materials. Sudan dyes I−IV were obtained from Dr. Ehrenstorfer GmbH (Augsburg, Germany). Acetonitrile was purchased from Fisher Scientific (Waltham, MA, USA). All other chemicals and solvents such as HPLC grade isopropyl alcohol and formic acid were purchased from Kermel Chemical Co. Ltd. (Tianjin, China). Ultrapure water was produced by using a Master-S UVF ultrapure water system (Shanghai, China). Stock standard solutions of Sudan dyes I−IV (100 mg/kg) were prepared with acetonitrile in a volumetric flask and stored at 4 °C in the dark. Intermediate working mix solutions at 1 mg/kg were obtained by appropriate dilution of the stock solution with acetonitrile. Apparatus. All analyses were performed on an Acquity TQD ultraperformance liquid chromatography (UPLC) system equipped 4073

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centrifugation (H-2050R model freezing centrifuge, Changsha Xiangyi centrifuge equipment Co., Ltd., Changsha, China) at 10000 rpm for 5 min at 5 °C, supernatants of samples were filtered through a 0.22 μm syringe filter into a 2 mL screw-cap vial. Then, 10 μL of this solution were injected into UPLC-MS/MS for analysis. The pesticide samples were 0.5 mL and dissolved in 10 mL of cyclohexane/ethyl acetate (50:50, v/v), then purified through a PrepLinc gel permeation chromatography (GPC) system (J2 Scientific, Columbia, MD, USA) and eluted with cyclohexane/ethyl acetate (50:50, v/v) at a flow rate of 5 mL/min using a modification of the method of Song et al.26 Finally, the eluates were evaporated and redissolved with acetonitrile, followed by filtering through a 0.22 μm syringe filter into a 2 mL screw-cap vial awaiting UPLC-MS/MS analysis. UPLC-MS/MS Conditions. A 50 mm × 2.1 mm × 5 μm reversed phase C18 Waters Acquity BEH column, heated at 35 °C, was eluted using a mixture of acetonitrile (A) and 0.1% formic acid water solution (B) at a flow rate of 0.35 mL/min. The gradient elution was realized as follows: 0−0.5 min, 70% A; 0.5−3.0 min, 70−95% A; 3.0−4.0 min, 95% A; 4.0−5.0 min, 95−70% A. The optimized experimental design parameters for ESI were as follows: capillary voltage, 1.0 kV; extractor cone voltage, 3.0 V; RF lens, 0.0 V; source temperature, 120 °C; desolvation temperature, 420 °C; desolvation gas flow, 700 L/h; cone gas flow, 50 L/h. The qualitative ion pairs of Sudan dyes I−IV as well as the cone voltage and the collision energy are shown in Table 2. Data Analysis. Qualitative analysis was performed by comparing the retention times of qualitative ion pair peaks of the samples with those of standard chromatograms. Quantification was based on the external standard method. The matrix-matched standard curve of paprika fruit was done with blank samples spiked with 10 gradient concentrations of Sudan dyes I−IV immediately prior to UPLC-MS/ MS analysis. The concentrations of Sudan dyes were then quantified by comparing the peak area of the particular compound in sample extracts with the corresponding external standard after replicate analysis. Quality Assurance. Standard solutions of Sudan dyes I−IV were run at the beginning of the sample analysis to determine the relative response factors and evaluate peak resolution. A solvent blank was processed through the entire procedure and analyzed prior to and after each set of eight samples. Each sample analysis was set up in duplicate. Results were considered invalid when the difference between duplicate analyses was >10% of the mean value of three values. Any sample showing no response or less than the limit of quantitation (LOQ) was concentrated to recheck or else reported as nondetected (ND).

Confirmation of Sudan I Contamination in Paprika Fruit. Figures 1 and 2 depict the UPLC-MS/MS chromato-

Figure 2. UPLC-MS/MS MRM trace obtained from standard solution (0.5 μg/kg) of Sudan I (A, B) and paprika sample of Sudan I (C, D).

graphic separation of Sudan dyes I, II, III, and IV in a standard solution (0.5 μg/kg) and a random paprika fruit sample. The retention times of standard solution are 1.44 min for Sudan I, 2.18 min for Sudan II, 2.91 min for Sudan III, and 4.90 min for Sudan IV, whereas for the paprika sample, only a Sudan I peak is observed at 1.47 min; Sudan dyes II, III, and IV were not detected, suggesting that Sudan dyes II, III, and IV did not exist in the paprika sample. Further analysis showed that the abundance ratio of Sudan I between the two ions of m/z 249.3 → 156.1 and 249.3 → 93.1 (qualitative ion pair) in paprika sample was 0.48 and 2.1% higher than that of the standard (0.47), which was within the acceptable deviations (±20%).27 Therefore, it was concluded that only Sudan I contamination occurred in the paprika fruit. Level of Sudan I Contamination in Paprika Fruit. Sudan I levels in paprika fruits and paprika stems from seven fields in Xinjiang (China) were investigated in triplicate (three aliquots of the same sample individually extracted and injected). As shown in Table 2, ultratrace levels of Sudan I contamination occurred in not only all paprika fruits but also the corresponding paprika stems. Considering all samples were directly collected by researchers from the field, neither addition nor cross-contamination occurred during the sample preparation and analysis processes, indicating that Sudan I contamination in paprika had really occurred over its growth period and was a universal phenomenon in the surveyed regions.

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RESULTS AND DISCUSSION Analytical Performance of UPLC-MS/MS for Sudan Dyes. UPLC-MS/MS displays outstanding advantages in both rapidly identifying Sudan dyes and accurately quantitating the amount at ultratrace levels and, thus, was selected to determine the Sudan dye contamination in this study. The major analytical performances of the method for Sudan dyes I−IV were investigated. As shown in Table 1, the limit of detection (LOD) and the limit of quantitation (LOQ) of 0.05− 0.12 and 0.09−0.31 μg/kg were estimated on the basis of 3 and 10 times the signal-to-noise ratio (S/N), respectively. Recovery experiments were carried out by spiking three different concentrations (0.4, 4.0, 10.0 μg/kg) of standard solutions into a selected sample. The mean recovery was in the range of 70.4−91.5%. The precision of the analytical method was evaluated by repeatedly analyzing the spiked samples five times, yielding reproducible responses with the relative standard deviation of 7.3−12.4%. Sudan dyes I−IV exhibited good linearity (R2 ≥ 0.9990), indicating this method offered improved sensitivity. 4074

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Table 3. Concentrations of Sudan I in Different Agronomic Materials (Soil, Pesticide, Fertilizer, Mulching Film, Coated Seed, and Irrigation Water) from Different Fields (Mean ± SE, n = 3) field

a

soil (μg/kg)

pesticide (μg/kg)

fertilizer (μg/kg)

mulching film (μg/kg)

coated seed (μg/kg)

irrigation water (μg/kg)

1 2 3

0.0180 ± 0.0005 0.0090 ± 0.0004 0.0120 ± 0.0005

0.75 ± 0.04 0.50 ± 0.03 0.62 ± 0.02

0.03 ± 0.02 0.02 ± 0.01 0.04 ± 0.02

NDa ND ND

0.03 ± 0.02 0.04 ± 0.01 0.07 ± 0.03

ND ND ND

mean

0.013

0.62

0.03

ND

0.05 ± 0.02

ND

Not detected. All samples were prepared independently.

The spatial variability of Sudan I was investigated by comparing the concentrations of Sudan I in five mature urn samples from different fields. As seen from Table 2, variability of the Sudan I levels of the same type changed with fields, with the maximum value of 1.08 μg/kg in field 5 and the minimum value of 0.26 μg/kg in field 2. Conversations with farmers revealed that such a large difference among fields (p < 0.05) was possibly attributable to the different operating conditions among different farmers. To assess the evolution of Sudan I level over different stages of maturation, green paprika, orange paprika, and red paprika samples were collected from four fields (fields 1, 2, 3, and 6) for analysis. As shown in Table 2, no clear variation tendency of Sudan I level was observed with respect to paprika colors; four values at the same maturity stage were averaged, and the mean concentrations were 0.53 μg/kg for green paprika, 0.44 μg/kg for orange paprika, and 0.50 μg/kg for red paprika. These findings suggested that the Sudan I level remained almost unchanged with various maturation periods, and there may be no enrichment or degradation of Sudan I during the maturation process of paprika fruit. Source of Sudan I Contamination in Paprika Fruits. To trace the source of Sudan dye contamination in paprika fruits, Sudan dye concentrations in reagents used in experiments, soils, and several agronomic materials, including pesticide, fertilizer, mulching film, coated seed, and irrigation water, were determined. No Sudan dyes were detected in any of the reagents used. Sudan dyes II, III, and IV were never detected in any samples, and Sudan I was detected only in soils, pesticides, fertilizers, and coated seeds (Table 3). Generally, about 10.00 g of fertilizer, 0.03 g of pesticide, and 60.00 g of rhizosphere soil are applied in the process from sowing to maturity for a paprika fruit; however, only 0.008 g of coated seed is used. With this planting mode taken into account, the total amount of Sudan I in soils, pesticides, and fertilizers seems to correlate well with Sudan I concentration in paprika fruits (Table 4). Moreover,

the mean Sudan I contents in soils, pesticides, and fertilizers were at least 2 orders of magnitude higher than that in coated seeds. These all together provide evidence for the major contribution of pesticide, fertilizer, and soil to Sudan I contamination in paprika fruit during its vegetation period. During paprika cropping, Sudan I from the fertilizer may be absorbed by the root and transported to other parts of the plant including the stem and fruit. When pesticides are sprayed, Sudan I from the pesticide may be absorbed by the fruit or absorbed by the soil and then transported to the fruit. Soil contamination of planting areas may come from cumulative agriculture practices for many years due to application of Sudan I-containing pesticide and fertilizer, and when paprika was planted in the Sudan I-contaminated soil, Sudan I may migrate from the soil to different parts of the plant including the fruit. As for the source of Sudan I in the pesticide and fertilizer, it can be traced to usage of Sudan dyes in chemical industry. Sudan dyes I−IV are widely used for different industrial and scientific applications such as oils, fats, plastics, printing inks, waxes, and spirit varnishing, among others,28 which were often used as raw and auxiliary materials in manufacturing agronomic materials or in their packaging due to great access. Therefore, the most effective way of controlling Sudan I contamination in paprika is to eliminate the abuse of Sudan dyes in the manufacture of agronomic materials and packages. To our knowledge, the present study is the first to report the occurrence of sub parts per billion levels of Sudan I contamination in paprika fruits in the process of growth. The Sudan I-contaminated soil combined with application of Sudan I-containing agronomic materials contributes to paprika fruit contamination. Due to the widespread use of Sudan Icontaining agronomic materials during agricultural production, soils are contaminated with Sudan I to some extent, which results in the Sudan I contamination in paprika in conjunction with the effect of agronomic materials during the growth period. This discovery has significant implication for reevaluating the origin of Sudan I in paprika fruits and paprika products.

Table 4. Total Amounts of Fruit, Soil, Pesticide, Fertilizer, Coated Seed per Fruit, and Total Amount of Sudan I in These Materials per Fruit sample fruit soil pesticide fertilizer coated seed

total amount (μg) used per fruit 5.0 6.0 9.0 1.0 8.0

× × × × ×

106 107 104 107 103

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total amount (μg) of Sudan I in materialsa 9.0 6.0 (4.5−6.9) (2.0−4.0) (2.4−5.6)

× × × × ×

ASSOCIATED CONTENT

S Supporting Information *

Type and amount of samples collected from different fields, compound-specific UPLC-ESI-MS/MS parameters for Sudan dyes I−IV, analytical method validation for other sample matrices (soil, pesticide, fertilizer, mulching film, coated seed, and irrigation water), and UPLC-MS/MS MRM trace obtained from standard solution (0.5 μg/kg) and paprika sample of Sudan II, Sudan III, and Sudan IV. This material is available free of charge via the Internet at http://pubs.acs.org.

10−4−5.4 × 10−3 10−4−1.2 × 10−3b 10−5 10−4 10−7

a

The amount range represented the different values for different species. bThe data were calculated by using the rhizosphere soil. 4075

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Article

(15) Han, D.; Yu, M.; Knopp, D.; Niessner, R.; Wu, M.; Deng, A. P. Development of a highly sensitive and specific enzyme-linked immunosorbent assay for detection of Sudan I in food samples. J. Agric. Food Chem. 2007, 55, 6424−6430. (16) Wang, Y. Z.; Wei, D. P.; Yang, H.; Yang, Y.; Xing, W. W.; Li, Y.; Deng, A. P. Development of a highly sensitive and specific monoclonal antibody-based enzyme-linked immunosorbent assay (ELISA) for detection of Sudan I in food samples. Talanta 2009, 77, 1783−1789. (17) Xu, T.; Wei, K. Y.; Wang, J.; Eremin, S. A.; Liu, S. Z.; Li, Q. X.; Li, J. Development of an enzyme-linked immunosorbent assay specific to Sudan red I. Anal. Biochem. 2010, 405, 41−49. (18) Du, M. J.; Han, X. G.; Zhou, Z. H.; Wu, S. G. Determination of Sudan I in hot chili powder by using an activated glassy carbon electrode. Food Chem. 2007, 105, 883−888. (19) Liu, Y. H.; Song, Z. H.; Dong, F. X.; Zhang, L. Flow injection chemiluminescence determination of Sudan I in hot chilli sauce. J. Agric. Food Chem. 2007, 55, 614−617. (20) RASFF. Rapid Alert System for Food and Feed; available at http://ec.europa.eu/food/food/rapidalert/indexen.htm/ (accessed Sept 13, 2012). (21) Schummer, C.; Sassel, J.; Bonenberger, P.; Moris, G. Low-level detections of Sudan I, II, III and IV in spices and chili-containing foodstuffs using UPLC-ESI-MS/MS. J. Agric. Food Chem. 2013, 61, 2284−2289. (22) American Spice Trade Association (ASTA). Sudan red and related dyes − white paper [EB/OL]; http://www.astaspice.org/files/ public/SudanWhitePaper.pdf, 2005 (accessed Dec 12, 2013). (23) Summary record of the standing committee on the food chain and animal health held in Brussels on 14 December 2006; SANCOD1(06)D/413447; European Commission: Brussels, Belgium, 2006; http://ec.europa.eu/food/committees/regulatory/scfcah/toxic/ summary 23_en. pdf (accessed Nov 29, 2013). (24) Hoenicke, K. Detection of low amounts of Sudan dyed and other illegal dyes in food and oleoresins. Analytical Artefact or CrossContamination? Europe Section of AOAC International Limassol, Cyprus; Nov 6−7, 2006; http://www.aoaceurope.com/ katrinhoenicke.pdf (accessed Sept 13, 2012). (25) European Commission, Health and Consumer Protection Directorate General, Committee IV − Food Safety in Production and Currency, Part III − Physical and Chemical Substances Surveillance. New Method Declaration, March 1999. (26) Song, H.; Lian, G. Y.; Du, L. J.; Li, H. P.; Xue, P.; Yuan, L.; Song, J.; Li, B. P. Determination of Para Red and Sudan red dyes in Capsicum and Capsicum products by high performance liquid chromatography with GPC. Food Sci. 2006, 27, 611−613. (27) Commission of the European Communities. Off. J. Eur. Communities 2002, L221, 8−36 (2002/657/EC). (28) Ertaş, E.; Ö zer, H.; Alasalvar, C. A rapid HPLC method for determination of Sudan dyes and Para Red in red chilli pepper. Food Chem. 2007, 105, 756−760.

AUTHOR INFORMATION

Corresponding Author

*(W.G.) Phone: +86 310 885 9305. Fax: +86 310 885 9306. Email: [email protected]. Funding

The present work was supported by the National International S&T Cooperation Project (No. 2014DFA31220). Notes

The authors declare no competing financial interest.

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